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Chapter 62 - Minerals and Agricultural Chemicals

MINERALS*

*Adapted from 3rd edition, Encyclopaedia of Occupational Health and Safety. Revision includes information from A. Bruusgaard, L.L. Cash, Jr., G. Donatello, V. D’Onofrio, G. Fararone, M. Kleinfeld, M. Landwehr, A. Meiklejohn, J.A. Pendergrass, S.A. Roach, T.A. Roscina, N.I. Sadkovskaja and R. Stahl.

Minerals are used in ceramics, glass, jewellery, insulation, stone carving, abrasives, plastics and numerous other industries in which they present primarily an inhalation hazard. The amount and type of impurities within the minerals may also determine the potential hazard associated with inhalation of the dust. The major concern during mining and production is the presence of silica and asbestos. The silica content in different rock formations, such as sandstone, feldspars, granite and slate, may vary from 20% to nearly 100%. It is therefore imperative that worker exposure to dust concentrations be kept to a minimum by the implementation of strict dust-control measures.

Improved engineering controls, wet drilling, exhaust ventilation and remote handling are recommended to prevent the development of lung disease in mineral workers. Where effective engineering controls are not possible, workers should wear approved respiratory protection, including the proper selection of respirators. Where possible, industrial substitution of less hazardous agents can reduce occupational exposure. Finally, the education of workers and employers regarding the hazards and proper control measures is an essential component of any prevention programme.

Regular medical examinations of mineral-dust-exposed workers should include evaluations for respiratory symptoms, lung function abnormalities and neoplastic disease. Workers showing the first signs of lung changes should be assigned to other jobs entailing no dust hazards. In addition to individual reports of illness, data from groups of workers should be collected for prevention programmes. The chapter Respiratory system provides more detail on the health effects of several of the minerals described here.

Apatite (Calcium Phosphate)

Occurrence and uses. Apatite is a natural calcium phosphate, usually containing fluorine. It occurs in the earth’s crust as phosphate rock, and it is also the chief component of the bony structure of teeth. Deposits of apatite are located in Canada, Europe, the Russian Federation and the United States.

Apatite is used in laser crystals and as a source of phosphorus and phosphoric acid. It is also employed in the manufacture of fertilizers.

Health hazards. Skin contact, inhalation or ingestion may cause irritation of skin, eyes, nose, throat or gastric system. Fluorine may be present in the dust and may cause toxic effects.

Asbestos

Occurrence and uses. Asbestos is a term used to describe a group of naturally occurring fibrous minerals which are widely distributed throughout the world. The asbestos minerals fall into two groups—the serpentine group, which includes chrysotile, and the amphiboles, which include crocidolite, tremolite, amosite and anthophyllite. Chrysotile and the various amphibole asbestos minerals differ in crystalline structure, in chemical and surface characteristics, and in the physical characteristics of their fibres.

The industrial features which have made asbestos so useful in the past are the high tensile strength and flexibility of the fibres, and their resistance to heat and abrasion and to many chemicals. There are many manufactured products which contain asbestos, including construction products, friction materials, felts, packings and gaskets, floor tiles, paper, insulation and textiles.

Health hazards. Asbestosis, asbestos-related pleural disease, malignant mesothelioma and lung cancer are specific diseases associated with exposure to asbestos dust. The fibrotic changes which characterize the pneumoconiosis, asbestosis, are the consequence of an inflammatory process set up by fibres retained in the lung. Asbestos is discussed in the chapter Respiratory system.

Bauxite

Occurrence and uses. Bauxite is the principal source of aluminium. It consists of a mixture of minerals formed by the weathering of aluminium-bearing rocks. Bauxites are the richest form of these weathered ores, containing up to 55% alumina. Some lateritic ores (containing higher percentages of iron) contain up to 35% Al2O3. The commercial deposits of bauxite are mainly gibbsite (Al2O3×3H2O) and boehmite (Al2O3×H2O), and are found in Australia, Brazil, France, Ghana, Guinea, Guyana, Hungary, Jamaica and Surinam. Gibbsite is more readily soluble in sodium hydroxide solutions than boehmite, and is therefore preferred for alumina production.

Bauxite is extracted by open-cast mining. The richer ores are used as mined. The lower-grade ores may be upgraded by crushing and washing to remove clay and silica waste.

Health hazards. Severe pulmonary disability has been reported in workers employed on smelting bauxite that is combined with coke, iron and very small amounts of silica. The affliction is known as “Shaver’s disease”. Because silica contamination of aluminium-containing ores is common, the health hazards associated with the presence of free crystalline silica in bauxite ores must be considered an important causal factor.

Clays (Hydrated Aluminium Silicates)

Occurrence and uses. Clay is a malleable plastic material formed by the weathered disintegration residues of argillaceous silicate rock; it usually contains 15 to 20% water and is hygroscopic. It occurs as a sediment in many geological formations in all parts of the world and contains in varying amounts feldspars, mica and admixtures of quartz, calcspar and iron oxide.

The quality of clay depends on the amount of alumina in it—for example, a good porcelain clay contains about 40% alumina, and the silica content is as low as 3 to 6%. On average the quartz content of clay deposits is between 10 and 20%, but at worst, where there is less alumina than usual, the quartz content may be as high as 50%. Content may vary in a deposit, and separation of grades may take place in the pit. In its plastic state, clay can be moulded or pressed, but when fired it becomes hard and retains the shape into which it has been formed.

Clay is often extracted in open-cast pits but sometimes in underground mines. In open-cast pits the method of extraction depends on the quality of the material and the depth of the deposit; sometimes the conditions require the use of hand-operated pneumatic tools, but, wherever possible, mining is mechanized, using excavators, power shovels, clay cutters, deep digging machines and so on. The clay is taken to the surface by truck or cable transport. The clay brought to the surface may be subjected to preliminary processing before dispatch (drying, crushing, pugging, mixing and so on) or it may be sold whole (see the chapter Mining and quarrying). Sometimes, as in many brickyards, the clay pit may be adjacent to the factory where the finished articles are made.

Different types of clay form the basic material in the manufacture of pottery, bricks and tiles, and refractories. Clay may be used without any processing in dam construction; in situ, it sometimes serves as a cover for gas stored in lower stratum. Appropriate ventilation and engineering controls are required.

Health hazards. Clays usually contain large amounts of free silica, and chronic inhalation can cause silicosis. Skin contact with wet clay may cause skin drying and irritation. There is a silicosis risk to underground workers where there is mechanized mining of clay with a high quartz content and little natural moisture. Here the decisive factor is not merely the quartz content but also the natural dampness: if the moisture level is less than 12%, much fine dust must be expected in mechanical extraction.

Coal

Occurrence and uses. Coal is a natural, solid, combustible material formed from prehistoric plant life. It occurs in layers or veins in sedimentary rocks. Conditions suitable for the natural formation of coal occurred between 40 and 60 million years ago in the Tertiary Age (brown-coal formation) and over 250 million years ago in the Carboniferous Age (bituminous-coal formation), when swampland forests thrived in a hot climate and then gradually subsided during ensuing geological movements. The main deposits of brown coal are found in Australia, eastern Europe, Germany, the Russian Federation and the United States. Major reserves of bituminous coal are located in Australia, China, India, Japan, the Russian Federation and the United States.

Coal is an important source of chemical raw materials. Pyrolysis or destructive distillation yields coal tar and hydrocarbon gases, which can be upgraded by hydrogenation or methanation to synthetic crude oil and fuel gas. Catalytic hydrogenation yields hydrocarbon oils and gasoline. Gasification produces carbon monoxide and hydrogen (synthetic gas), from which ammonia and other products can be made. While in 1900, 94% of the world’s energy requirements were met by coal and only 5% by petroleum and natural gas, coal has been increasingly replaced by liquid and gaseous fuels throughout the world.

Health hazards. Hazards of mining and of coal dust are discussed in the chapters Mining and quarrying and Respiratory system.

Corundum (Aluminium Oxide)

Occurrence and uses. Corundum is one of the principal natural abrasives. Natural corundum and artificial corundum (alundum or artificial emery) are usually relatively pure. The artificial material is produced from bauxite by smelting in an electric furnace. Because of its hardness, corundum is used to shape metals, wood, glass and ceramics, by a process of grinding or polishing. Health hazards are discussed elsewhere in this Encyclopaedia.

Diatomaceous Earth (Diatomite, Kieselguhr, Infusorial Earth)

Occurrence and uses. Diatomaceous earth is a soft, bulky material composed of skeletons of small, prehistoric aquatic plants related to algae (diatoms). Certain deposits comprise up to 90% free amorphous silica. They have intricate geometric forms and are available as light-coloured blocks, bricks, powder and so on. Diatomaceous earth absorbs 1.5 to 4 times its weight of water and has a high oil absorption capacity. Deposits occur in Algeria, Europe, the Russian Federation and the western United States. Diatomaceous earth may be used in foundries, in paper coating, in ceramics and in the maintenance of filters, abrasives, lubricants and explosives. It is used as a filtering medium in the chemical industry. Diatomaceous earth also finds use as a drilling-mud thickener; an extender in paints, rubber and plastic products; and as an anti-caking agent in fertilizers.

Health hazards. Diatomaceous earth is highly respirable. For many industrial purposes diatomaceous earth is calcined at 800 to 1,000 ºC to produce a greyish-white powder called kieselguhr, which may contain 60% or more crystobalite. During mining and processing of diatomaceous earth, the risk of death from both respiratory diseases and lung cancer has been related to the inhalation of dust as well as to cumulative crystalline silica exposures, as discussed in the chapter Respiratory system.

Erionite

Occurrence and uses. Erionite is a crystalline, fibrous zeolite. Zeolites, a group of alumino-silicates found in the cavities of volcanic rocks, are used in the filtration of hard water and in the refining of oil. Erionite occurs in California, Nevada and Oregon in the United States, and in Ireland, Iceland, New Zealand and Japan.

Health hazards. Erionite is a known human carcinogen. Chronic inhalation may cause mesothelioma.

Feldspar

Occurrence and uses. Feldspar is a general name for a group of sodium, potassium, calcium and barium aluminium silicates. Commercially, feldspar usually refers to the potassium feldspars with the formula KAlSi3O8, usually with a little sodium. Feldspar occurs in the United States. It is used in pottery, enamel and ceramic ware, glass, soaps, abrasives, cements and concretes. Feldspar serves as a bond for abrasive wheels, and it finds use in insulating compositions, tarred roofing materials and fertilizers.

Health hazards. Chronic inhalation may cause silicosis due to the presence of substantial amounts of free silica. Feldspars may also contain irritating sodium oxide (soda spars), potassium oxide (potash spars), and calcium oxide (lime spars) in insoluble form. See the section “Silica” below.

Flint

Occurrence and uses. Flint is a crystalline form of native silica or quartz. It occurs in Europe and the United States. Flint is used as an abrasive, a paint extender and a filler for fertilizer. In addition, it finds use in insecticides, rubber, plastics, road asphalt, ceramics and chemical tower packing. Historically, flint has been an important mineral because it was used to make some of the first known tools and weapons.

Health hazards are related to the toxic properties of silica.

Fluorspar (Calcium Fluoride)

Occurrence and uses. Fluorspar is a mineral that contains 90 to 95% calcium fluoride and 3.5 to 8% silica. It is extracted by drilling and blasting. Fluorspar is a principal source of fluorine and its compounds. It is used as a flux in open hearth steel furnaces and in metal smelting. In addition, it finds use in the ceramics, paint and optical industries.

Health hazards. The hazards of fluorspar are due primarily to the harmful effects of the fluorine content and its silica content. Acute inhalation may cause gastric, intestinal, circulatory and nervous system problems. Chronic inhalation or ingestion may cause loss of weight and appetite, anaemia, and bone and teeth defects. Pulmonary lesions have been reported among persons inhaling dust containing 92 to 96% calcium fluoride and 3.5% silica. It appears that calcium fluoride intensifies the fibrogenic action of silica in the lungs. Cases of bronchitis and silicosis have been reported among fluorspar miners.

In the mining of fluorspar, dust control should be carefully enforced, including wet drilling, watering of loose rock, and exhaust and general ventilation. When heating fluorspar, there is also the hazard of hydrofluoric acid being formed, and the relevant safety measures should be applied.

Granite

Occurrence and uses. The coarse-grained igneous rock granite consists of quartz, feldspar and mica in shapeless interlocking grains. It finds use as crushed granite and as dimension granite. After it is crushed to the required size, granite may be used for concrete aggregate, road metal, railroad ballast, in filter beds, and for riprap (large chunks) in piers and breakwaters. The colors—pink, grey, salmon, red and white—are desirable for dimension granite. The hardness, uniform texture and other physical properties make dimension granite ideal for monuments, memorials, foundation blocks, steps and columns.

Large production of crushed granite comes mainly from California, with substantial amounts from the other US States of Georgia, North Carolina, South Carolina and Virginia. Major production areas of dimension granite in the United States include Georgia, Maine, Massachusetts, Minnesota, North Carolina, South Dakota, Vermont, and Wisconsin.

Health hazards. Granite is heavily contaminated with silica. Therefore, silicosis is a major health hazard in granite mining.

Graphite

Occurrence and uses. Graphite is found in almost every country of the world, but the majority of production of the natural ore is limited to Austria, Germany, Madagascar, Mexico, Norway, the Russian Federation and Sri Lanka. Most, if not all, natural graphite ores contain crystalline silica and silicates.

Lump graphite is found in veins which cross different types of igneous and metamorphic rock containing mineral impurities of feldspar, quartz, mica, pyroxine, zircon, rutile, apatite and iron sulphides. The impurities are often in isolated pockets in the veins of ore. Mining is commonly underground, with hand drills for selective mining of narrow veins.

Deposits of amorphous graphite are also underground, but usually in much thicker beds than the veins of lumps. Amorphous graphite is commonly associated with sandstone, slate, shale, limestone and adjunct minerals of quartz and iron sulphides. The ore is drilled, blasted and hand-loaded into wagons and brought to the surface for grinding and impurity separation.

Flake graphite is usually associated with metamorphosed sedimentary rock such as gneiss, schists and marbles. The deposits are often on or near the surface. Consequently, normal excavating equipment such as shovels, bulldozers and scarifiers are used in open-cast mining, and a minimum of drilling and blasting is necessary.

Artificial graphite is produced by the heating of coal or petroleum coke, and generally contains no free silica. Natural graphite is used in the manufacture of foundry linings, lubricants, paints, electrodes, dry batteries and crucibles for metallurgical purposes. The “lead” in pencils is also graphite.

Health hazards. Inhalation of carbon, as well as associated dusts, may occur during the mining and milling of natural graphite, and during the manufacture of artificial graphite. X-ray examinations of natural and artificial graphite workers have shown varying classifications of pneumoconioses. Microscopic histopathology has revealed pigment aggregates, focal emphysema, collagenous fibrosis, small fibrous nodules, cysts and cavities. The cavities have been found to contain an inky fluid in which graphite crystals were identified. Recent reports note that the materials implicated in exposures leading to severe cases with massive pulmonary fibrosis are likely to be mixed dusts.

Graphite pneumoconiosis is progressive even after the worker has been removed from the contaminated environment. Workers may remain asymptomatic during many years of exposure, and disability often comes suddenly. It is essential that periodic analyses are made of the raw ore and airborne dust for crystalline silica and silicates, with special attention to feldspar, talc and mica. Acceptable dust levels must be adjusted to accommodate the effect these disease-potentiating dusts may have on workers’ health.

In addition to being exposed to the physical hazards of mining, graphite workers may also face chemical hazards, such as hydrofluoric acid and sodium hydroxide used in graphite purification. Protection against the risks associated with these chemicals should be part of any health programme.

Gypsum (Hydrated Calcium Sulphate)

Occurrence and uses. Though it occurs throughout the world, gypsum is rarely found pure. Gypsum deposits may contain quartz, pyrites, carbonates and clayey and bituminous materials. It occurs in nature in five varieties: gypsum rock, gypsite (an impure, earthy form), alabaster (a massive, fine-grained translucent variety), satin spar (a fibrous silky form) and selenite (transparent crystals).

Gypsum rock may be crushed and ground for use in the dihydrate form, calcined at 190 to  200 ºC (thus removing part of the water of crystallization) to produce calcium sulphate hemihydrate or plaster of Paris, or completely dehydrated by calcining at over 600 ºC to produce anhydrous or dead-burned gypsum.

Ground dihydrate gypsum is used in the manufacture of Portland cement and artificial marble products; as a soil conditioner in agriculture; as a white pigment, filler or glaze in paints, enamels, pharmaceuticals, paper and so on; and as a filtration agent.

Health hazards. Workers employed in the processing of gypsum rock may be exposed to high atmospheric concentrations of gypsum dust, furnace gases and smoke. In gypsum calcining, workers are exposed to high environmental temperatures, and there is also the hazard of burns. Crushing, grinding, conveying and packaging equipment presents a danger of machinery accidents. The pneumoconiosis observed in gypsum miners has been attributed to silica contamination.

Dust formation in gypsum processing should be controlled by mechanization of dusty operations (crushing, loading, conveying and so on), addition of up to 2% by volume of water to gypsum prior to crushing, use of pneumatic conveyors with covers and dust traps, enclosure of dust sources and provision of exhaust systems for kiln openings and for conveyor transfer points. In the workshops containing the calcining kilns, it is advisable to face the walls and floors with smooth materials to facilitate cleaning. Hot piping, kiln walls and drier enclosures should be lagged to reduce the danger of burns and to limit heat radiation to the work environment.

Limestone

Occurrence and uses. Limestone is a sedimentary rock composed mainly of calcium carbonate in the form of mineral calcite. Limestones may be classified either according to the impurities they contain (dolomitic limestone, which contains substantial amounts of magnesium carbonate; argillaceous limestone, with a high clay content; siliceous limestone, which contains sand or quartz; and so on) or according to the formation in which they occur (e.g., marble, which is a crystalline limestone). Limestone deposits are widely distributed throughout the earth’s crust and are extracted by quarrying.

Since early times, limestone has been used as a building stone. It is also crushed for use as a flux in smelting, in refining, and for the manufacture of lime. Limestone is used as hardcore and ballast in road and railway construction, and it is mixed with clay for the manufacture of cement.

Health hazards. During extraction, the appropriate quarrying safety measures should be taken, and machinery-guarding principles should be observed on crushers. The main health hazard in limestone quarries is the possible presence, in the airborne limestone dust, of free silica, which normally accounts for 1 to 10% of limestone rock. In studies of limestone quarry and processing workers, x-ray examinations revealed pulmonary changes, and clinical examination showed pharyngitis, bronchitis and emphysema. Workers dressing stone for construction work should observe the safety measures appropriate to the stone industry.

Marble (Calcium Carbonate)

Occurrence and uses. Marble is geologically defined as a metamorphosed (re-crystallized) limestone composed primarily of crystalline grains of calcite, dolomite, or both, having a visible crystalline texture. Long usage of the term marble by the quarry and finishing industry has led to the development of the term commercial marble, which includes all crystalline rock capable of taking a polish and composed primarily of one or more of the following minerals: calcite, dolomite or serpentine.

Marble has been utilized throughout historic time as an important construction material because of its strength, durability, ease of workability, architectural adaptability and aesthetic satisfaction. The marble industry comprises two major branches—dimension marble and crushed and broken marble. The term dimension marble is applied to deposits of marble quarried for the purpose of obtaining blocks or slabs that meet specifications as to size and shape. The uses of dimension marble include building stone, monumental stone, ashlar, veneer panelling, wainscotting, tiling, statuary and so on. Crushed and broken marble ranges in size from large boulders to finely ground products, and products include aggregates, ballast, roofing granules, terrazzo chips, extenders, pigments, agricultural lime and so on.

Health hazards. Occupational diseases specifically connected with the mining, quarrying and processing of marble itself have not been described. In underground mining there may be exposure to toxic gases produced by blasting and some types of motor-driven equipment; adequate ventilation and respiratory protection are necessary. In abrasive blasting there will be exposure to silica if sand is used, but silicon carbide or aluminium oxide are equally effective, carry no silicosis risk, and should be substituted. The large quantities of dust generated in processing marble should be subject to dust control, either by the use of moist methods or by exhaust ventilation.

Mica

Occurrence and uses. Mica (from the Latin micare, to gleam or sparkle) is a mineral silicate which occurs as a primary constituent of igneous rocks, particularly granites. It is also a common component of such silicate materials as kaolin, which are produced by the weathering of these rocks. In the rock bodies, particularly in the pegmatite veins, mica occurs as lenticular masses of cleavable sheets (known as books) of up to 1 m in diameter, or as particles. There are many varieties, of which the most useful are muscovite (common, clear or white mica), phlogopite (amber mica), vermiculite, lepidolite and sericite. Muscovite is generally found in siliceous rocks; there are substantial deposits in India, South Africa and the United States. Sericite is the small plate variety of muscovite. It results from the weathering of schists and gneisses. Phlogopite, which occurs in calcareous rocks, is concentrated in Madagascar. Vermiculite has the outstanding characteristic of expanding considerably when quickly heated to around 300 ºC. There are large deposits in the United States. The main value of lepidolite lies in its high content of lithium and rubidium.

Mica is still used for slow-combustion stoves, lanterns or peep-holes of furnaces. The supreme quality of mica is that it is dielectric, which makes it a top-priority material in aircraft construction. Mica powder is used in the manufacture of electric cables, pneumatic tyres, welding electrodes, bituminized cardboard, paints and plastics, dry lubricants, dielectric dressings and flameproof insulators. It is often compacted with alkyd resins. Vermiculite is widely used as an insulating material in the building industry. Lepidolite is used in the glass and ceramic industries.

Health hazards. When working with mica, the generation of static electricity is possible. Straightforward engineering techniques can harmlessly discharge it. Mica miners are exposed to the inhalation of a wide variety of dusts, including quartz, feldspar and silicates. Chronic inhalation may cause silicosis. Exposure of workers to mica powder may cause irritation of the respiratory tract, and, after several years, nodular fibrotic pneumoconiosis can occur. It was long considered to be a form of silicosis, but it is now believed not to be, because pure mica dust contains no free silica. The radiological appearance is often close to that of asbestosis. Experimentally, mica has proved to possess a low cytotoxicity on macrophages and to induce only a poor fibrogenic response limited to the formation of thick reticulin fibres.

Chronic inhalation of vermiculite, which often contains asbestos, may cause asbestosis, lung cancer and mesothelioma. Ingestion of vermiculite is also suspected in stomach and intestinal cancer.

Pumice

Occurrence and uses. Pumice is a porous rock, grey or white, fragile and of low specific gravity, coming from recent volcanic magma; it is composed of quartz and silicates (mainly feldspar). It is found either pure or mixed with various substances, chief among them obsidian, which differs by its shiny black colour and its specific gravity, which is four times greater. It occurs principally in Ethiopia, Germany, Hungary, Italy (Sicily, Lipari), Madagascar, Spain and the United States. Some varieties, such as Lipari pumice, have a high content of total silica (71.2 to 73.7%) and a fair amount of free silica (1.2 to 5%).

In commerce and for practical uses, a distinction is made between pumice in blocks and in powder. When it is in block form the designation differs according to the size of block, colour, porosity and so on. The powder form is classified by numbers according to grain size. Industrial processing comprises a number of operations: sorting to separate the obsidian, crushing and pulverizing in machines with stone or metal grinding wheels, drying in open kilns, sifting and screening using hand-operated flat and open sieves and reciprocating or rotating screens, the waste matter generally being recovered.

Pumice is used as an abrasive (block or powder), as a lightweight building material, and in the manufacture of stoneware, explosives and so on.

Health hazards. The most dangerous operations involving exposure to pumice are kiln drying and sifting, because of the large amount of dust produced. Apart from the characteristic signs of silicosis observed in the lungs and sclerosis of the hilar lymphatic glands, the study of some fatal cases has revealed damage to various sections of the pulmonary arterial tree. Clinical examination has revealed respiratory disorders (emphysema and sometimes pleural damage), cardiovascular disorders (cor pulmonale) and renal disorders (albuminuria, haematuria, cylindruria), as well as signs of adrenal deficiency. Radiological evidence of aortitis is more common and serious than in the case of silicosis. A typical radiological appearance of lungs in liparitosis is the presence of linear thickening due to lamellar atelactasis.

Sandstone

Occurrence and uses. Sandstone is a siliciclastic sedimentary rock consisting primarily of sand, usually sand that is predominantly quartz. Sandstones often are poorly cemented and can be easily crumbled into sand. Yet, strong, durable sandstone, with tan and grey colours, is used as dimension sandstone for exterior facing and trim for buildings, in houses, as curbstones, in bridge abutments and in various retaining walls. Firm sandstones are crushed for use as concrete aggregate, railroad ballast and riprap. However, many commercial sandstones are weakly cemented and therefore are crumbled and used for moulding sand and glass sand. Glass sand is the main ingredient in glass. In the metalworking industry, sand with good cohesiveness and refractoriness is used for making special shaped moulds into which molten metal is poured.

Sandstone is found throughout the United States, in Illinois, Iowa, Minnesota, Missouri, New York, Ohio, Virginia and Wisconsin.

Health hazards. The primary risks are from the silica exposure, which is discussed in the chapter Respiratory system.

Silica

Occurrence and uses. Silica occurs naturally in crystalline (quartz, cristobalite and tridymite), cryptocrystalline (e.g., chalcedony) and amorphous (e.g., opal) forms, and the specific gravity and melting point depend on the crystalline form.

Crystalline silica is the most widely occurring of all minerals, and it is found in most rocks. The most commonly occurring form of silica is the sand found on beaches throughout the world. The sedimentary rock sandstone consists of grains of quartz cemented together with clays.

Silica is a constituent of common glass and most refractory bricks. It is also used extensively in the ceramic industry. Rocks containing silica are used as common building materials.

Free and combined silica. Free silica is silica which is not combined with any other element or compound. The term free is used to distinguish it from combined silica. Quartz is an example of free silica. The term combined silica originates from the chemical analysis of naturally occurring rocks, clays and soils. The inorganic constituents are found to consist almost always of oxides bound chemically, commonly including silicon dioxide. Silica so combined with one or more other oxides is known as combined silica. The silica in mica, for example, is present in the combined state.

In crystalline silica, the silicon and oxygen atoms are arranged in a definite, regular pattern throughout the crystal. The characteristic crystal faces of a crystalline form of silica are the outward expression of this regular arrangement of atoms. The crystalline forms of free silica are quartz, cristobalite and tridymite. Quartz is crystallized in the hexagonal system, cristobalite in the cubic or tetragonal system and tridymite in the ortho-rhombic system. Quartz is colourless and transparent in the pure form. The colours in naturally occurring quartz are due to contamination.

In amorphous silica the different molecules are in a dissimilar spatial relationship one to another, with the result that there is no definite regular pattern between molecules some distance apart. This absence of long-range order is characteristic of amorphous materials. Cryptocrystalline silica is intermediate between crystalline and amorphous silica in that it consists of minute crystals or crystallites of silica which are themselves arranged in no regular orientation one to another.

Opal is an amorphous variety of silica with a varying amount of combined water. A commercially important form of amorphous silica is diatomaceous earth, and calcinated diatomaceous earth (kieselguhr). Chalcedony is a cryptocrystalline form of silica which occurs filling cavities in lavas or associated with flint. It is also found in the annealing of ceramics when, under certain temperature conditions, the quartz in silicates may crystallize out in minute crystals in the body of the ware.

Health hazards. The inhalation of airborne dust of silica gives rise to silicosis, a serious and potentially fatal fibrotic disease of the lungs. The chronic, accelerated, and acute forms of silicosis reflect differing exposure intensities, latency periods and natural histories. Chronic silicosis may progress to progressive massive fibrosis, even after exposure to silica-containing dust has ceased. Hazards of silica are discussed in more detail in the chapter Respiratory system.

Slate

Occurrence and uses. Slate is very fine-grained, sedimentary argillaceous or schisto-argillaceous rock, easily split, of a leaden-grey, reddish or greenish colour. The principal deposits are in France (Ardennes), Belgium, the United Kingdom (Wales, Cornwall), the United States (Pennsylvania, Maryland) and Italy (Liguria). With a high calcium carbonate content, they contain silicates (mica, chlorite, hydrosilicates), iron oxides and free silica, amorphous or crystalline (quartz). The quartz content of hard slates is in the region of 15%, and that of soft slates, less than 10%. In North Wales quarries, respirable slate dust contains between 13 and 32% of respirable quartz.

Slate slabs are used for roofing; stair treads; door, window and porch casements; flooring; fireplaces; billiard tables; electricity switch panels; and school blackboards. Powdered slate has been used as a filler or pigment in rustproofing or insulating paints, in mastics, and in paints and bituminous products for road surfacing.

Health hazards. Disease in slate workers has attracted attention since the early nineteenth century, and cases of “miner’s phthisis” uncomplicated by tubercle bacilli were described at an early date. Pneumoconiosis has been found in a third of workers studied in the slate industry in North Wales, and in 54% of slate pencil makers in India. Slateworkers’ pneumoconiosis may have features of silicosis due to the high quartz content of some slates. Chronic bronchitis and emphysema are frequently observed, especially in extraction workers.

The replacement of the hand pick by low-velocity mechanical equipment considerably reduces dust generation in slate quarries, and the use of local exhaust ventilation systems makes it possible to maintain airborne dust concentrations within acceptable limits for 8-hour exposure. Ventilation of underground workings, drainage of groundwater into pits, lighting and work organization are improving the general hygiene of working conditions.

Circular sawing should be carried out under water jets, but planing does not usually give rise to dust provided the slivers of slate are not allowed to fall to the ground. Larger sheets are usually wet-polished; however, where dry-polishing is carried out, well-designed exhaust ventilation should be employed since slate dust is not easily collected even when using scrubbers. The dust readily clogs bag filters.

Workshops should be cleaned daily to prevent accumulation of dust deposits; in certain cases, it may be preferable to prevent deposited dust in gangways from becoming airborne again by covering dust with sawdust rather than by wetting it.

Talc

Occurrence and uses. Talc is a hydrous magnesium silicate whose basic formula is (Mg Fe+2)3Si4O10 (OH2), with theoretical weight percentages as follows: 63% SiO2, 32% MgO and  5% H2O. Talc is found in a variety of forms and is frequently contaminated with other minerals, including silica and asbestos. Talc production occurs in Australia, Austria, China, France and the United States.

The texture, stability and fibrous or flaky properties of the various talcs have made them useful for many purposes. The purest grades (i.e., those which most nearly approximate the theoretical composition) are fine in texture and colour, and are therefore widely used in cosmetics and toilet preparations. Other varieties, containing admixtures of different silicates, carbonates and oxides, and perhaps free silica, are relatively coarse in texture and are used in the manufacture of paint, ceramics, automobile tyres and paper.

Health hazards. Chronic inhalation may cause silicosis if silica is present, or asbestosis, lung cancer, and mesothelioma if asbestos or asbestos-like minerals are present. Investigations of workers exposed to talc without associated asbestos fibres revealed trends for higher mortality from silicosis, silicotuberculosis, emphysema and pneumonia. The major clinical symptoms and signs of talc pneumoconiosis include chronic productive cough, progressive shortness of breath, diminished breath sounds, limited chest expansion, diffuse rales and clubbing of the finger tips. Lung pathology has revealed various forms of pulmonary fibrosis.

Wollastonite (Calcium Silicate)

Occurrence and uses. Wollastonite (CaSiO3) is a natural calcium silicate found in metamorphic rock. It occurs in many different forms in New York and California in the United States, in Canada, Germany, Romania, Ireland, Italy, Japan, Madagascar, Mexico, Norway and Sweden.

Wollastonite is used in ceramics, welding-rod coatings, silica gels, mineral wool and paper coating. It is also used as a paint extender, a soil conditioner, and as a filler in plastics, rubber, cements and wallboard.

Health hazards. Wollastonite dust may cause skin, eye and respiratory irritation.

AGRICULTURAL CHEMICALS

Gary A. Page

Agricultural chemicals are usually defined as pesticides, fertilizers and health products. The US Environmental Protection Agency (EPA) defines pesticides as any materials manufactured or formulated to kill a pest. This means that herbicides, fungicides, insecticides and miticides are pesticides. Fertilizers are nutrient chemicals that enhance the growth of the plant. The important elements in the fertilizers are nitrogen, phosphorus and potassium. Nitrogen is usually in the form of ammonia, ammonium nitrate, ammonium sulphate, ammonium phosphate or solutions of these materials. Other nitrogen-containing chemicals are used for some special nutrient needs. Ammonium phosphate is the normal source of phosphorous. Potash (potassium oxide) is the potassium nutrient. Animal health products are any chemicals that are used to promote the health or growth of an animal. This includes products that are used topically by drenching or pouring-on, orally as a tablet or gel, and injectibles.

Pesticides

The most significant development in the pesticide manufacturing industry has been the introduction of the environmentally friendly pesticides. The imidazolinone family of herbicides has been a benefit to soybean and other field crops, as the herbicides are much more effective pound for pound; are less toxic to humans, animals and fish; have less persistence in the soil; and are formulated using water instead of flammable solvents, as compared to the old generation nitroaromatics. Concurrent with these innovations is the development of imidazolinones-resistant seeds that can be protected from weed growth. Corn is in the forefront in this area and has been successfully grown, protected by the imidazolinones. This also makes carry-over from year to year of the herbicide an insignificant problem, as in many areas soybeans and corn are rotated.

A newer development is the production of the synthetic pyrethroids, which are broad-range pesticides. These products are effective pesticides and are less toxic to animals and humans than the old organophosphates and carbamates. They are activated by the insect’s biological system and therefore not a danger to vertebrates. They are also less persistent in the environment, as they are biodegradable. 

There have also been developments in the use of the old generation pesticides and herbicides. Herbicide formulations have been developed that utilize water dispersion technology that eliminates the use of volatile solvents. This not only reduces the amount of volatile organic chemicals that go to the atmosphere, but also makes handling, storage, formulation and transportation much safer. In the area of pesticides, a superior method of handling the toxic pesticides has been developed that uses closed container transfer of the material from the package to the spreader, called “Lock-N-Load”. This reduces the chances of exposure to these toxic materials. Organophosphates are still being used successfully to help eradicate health problems such as malaria and river blindness. Some of the less toxic organophosphates are effective in the treatment of animals for insects, worms and mites by direct application to the skin using pour-on or aerosol formulations.

The pesticide industry is regulated by many countries, and labelling, application to plants and soil, training in pesticide use, and transportation are controlled. Many pesticides can only be spread by licensed applicators. Precautions during pesticide application are discussed elsewhere in this Encyclopaedia. Bulk transportation vehicles can only be operated by qualified drivers. The producers of pesticide have a legal obligation to provide safe handling and application methods. This is usually accomplished by providing comprehensive labelling, training and material safety data sheets (MSDSs) (see the chapter Using, storing and transporting chemicals).

Another problem is the disposal of empty containers. It is not advisable, and in many places it is illegal, to reuse pesticide containers. Many advances have been made to mitigate this problem. Plastic containers have been collected by the distributors and reprocessed into plastic pipe. Bulk, refillable containers have been used. With the advent of the wettable powders and water-based dispersions, triple rinsing the container into the solutions tank gives the applicator a method to decontaminate the container before landfilling or recycling. Hand lances with spray nozzles that can pierce the container are used to assure proper cleaning and the destruction of the container so that it can not be reused.

Pesticides are made to kill; therefore, care is necessary to handle them safely. Some of the problems have been lessened by the product advances. In most cases, copious quantities of water are the best first-aid treatment for superficial exposures to skin and eyes. For ingestion, it is best to have a specific antidote available. It is important that the nearest health facility know what is being used and have a supply of the appropriate antidote on hand. For instance, organophosphates and carbamates cause cholinesterase inhibition. Atropine, the specific antidote for the treatment of this reaction, should be available wherever these pesticides are used.

For further discussion of pesticides, see the eponymous article in this chapter.

Fertilizers

Ammonia is the base of most important fertilizers. The major fertilizers are ammonia itself, ammonium nitrate, urea, ammonium sulphate and ammonium phosphate. There appears to be an environmental problem associated with nitrogen use, as the ground water in many farming areas is contaminated with nitrates, which causes health problems when the water is consumed as drinking water. There are pressures for farmers to use less fertilizer and to rotate crops of nitrogen-using legumes such as soy beans and rye grass. Ammonium nitrate, an oxidizer, is explosive if heated. The dangers of ammonium nitrate as a blasting agent were demonstrated by the destruction of a US federal building in Oklahoma City, Oklahoma, in 1995. There is some movement to add inert ingredients to make fertilizer-grade ammonium nitrate detonation-resistant. An industrial explosion resulting in multiple fatalities which occurred in an ammonium nitrate solutions plant that was thought to be safe from detonation because the ammonium nitrate was handled as an 85% solution is anonther example. Investigation results indicated that an intricate condition of temperature and contamination caused the incident. These conditions would not exist in the retail or farming sector. Anhydrous ammonia is a moderately toxic gas at room temperature and must be kept under pressure or refrigeration during storage and use. It is a skin, eye and respiratory irritant, can cause burns, and is flammable. It is directly applied to the soil or used as an aqueous solution. There is significant anhydrous ammonia storage in many farming areas. A hazardous condition is created if the storage is not managed correctly. This should include monitoring for leaks and emergency leak procedures.

Animal Health Products

The development and marketing of bovine somatotropin (BST) has caused controversy. BST, a fermentation product, raises the productivity of milk cows by 10 to 20%. Many people are opposed to the product because it introduces a chemical into the production of milk. However, the BST milk is indistinguishable from ordinary milk since BST is produced naturally by the milk cow. A problem seems to be an increase in infections of the cow’s udder. Antibiotics for these infections are available, but the use of these antibiotics is also controversial. The important benefits of BST are the increased production of milk with a reduction in food consumption and a similar reduction in cow manure, a material that is a solid-waste problem in many areas. A similar product, porcine somatotropin (PST), is still in the testing stage. It produces bigger hogs quickly, utilizing less feed, and results in pork containing less fat.

Antibiotic use in the beef-raising industry is also causing controversy. There is fear that consumption of large amounts of beef will result in hormonal problems in humans. There has been little in the way of confirmed problems, but the concern persists. Animal health products have been developed that control worms in animals. The previous generation was a synthetic chemical product, but the new generation products are the result of biological fermentation technology. These products are effective in many types of animals at very low use levels, and include domestic pets in their protection arena. These products are very toxic to aquatic life, though, so much care must be taken to avoid contamination of creeks and streams. These materials do biodegrade, so there appear to be no long-term or residual aquatic problems.

Manufacture of Agricultural Chemicals

The manufacturing of agricultural chemicals entails many processes and raw materials. Some agricultural chemicals are batch chemical syntheses that involve exothermic reactions where temperature control and emergency relief sizing are an issue. Hazard evaluations are necessary to assure that all the hazards are discovered and addressed. Hazard and operability studies (HAZOP) are recommended for conducting reviews. Relief sizing must be conducted using Design Institute for Emergency Relief Systems (DIERS) technology and data from calorimetric equipment. Usually, because of the complexity of the molecules, the production of agricultural chemicals involves many steps. Sometimes there is considerable aqueous and organic liquid waste. Some of the organics may be recyclable, but most of the aqueous waste must be biologically treated or incinerated. Both methods are difficult because of the presence of organic and inorganic salts. The previous generation herbicides, because they involved nitrations, were produced using continuous reactors to minimize the quantities of the nitrated materials at reaction temperatures. Severe runaway reactions, resulting in property damage and injuries, have occurred when batch reactors of nitrated organics have been subjected to a temperature excursion or contamination.

Many modern pesticide products are dry powders. If the concentration, particle size, oxygen concentration and a source of ignition are present at the same time, a dust explosion can occur. The use of inerting, the exclusion of oxygen, and utilization of nitrogen or carbon dioxide minimizes the oxygen source and can make the processes safer. These dusts may also be an industrial hygiene issue. Ventilation, both general and local, is a solutions to these problems.

The major fertilizers are made continuously rather than by the batch process. Ammonia is made by reforming methane at high temperatures utilizing a specific catalyst. Carbon dioxide and hydrogen are also formed and must be separated from the ammonia. Ammonium nitrate is made from ammonia and nitric acid in a continuous reactor. The nitric acid is formed by the continuous oxidation of ammonia on a catalytic surface. Ammonium phosphate is a reaction of ammonia and phosphoric acid. Phosphoric acid is made by reacting sulphuric acid with phosphate -containing ores. Sulphuric acid is formed by burning sulphur to sulphur dioxide, and catalytically converting the sulphur dioxide continuously to sulphur trioxide, and then adding water to form the sulphuric acid. Urea is a continuous high-pressure reaction of carbon dioxide and ammonia, the carbon dioxide usually coming from the ammonia continuous reaction by-product.

Many of these raw materials are toxic and volatile. Release of the raw materials or finished products, through an equipment failure or operator error, can expose employees and others in the community. A detailed emergency response plan is a necessary tool to minimize the effects of a release. This plan should be developed by determining a credible worst-case event through hazard evaluations and then forecasting consequences using dispersion modelling. This plan should include a method to notify employees and the community, an evacuation plan, emergency services and a recovery plan.

Transportation of agricultural chemicals should be thoroughly investigated to choose the safest route—one that minimizes the exposures if an incident occurs. A transportation emergency response plan should be implemented to address transportation incidents. This plan should include a published emergency response telephone number, company personnel to respond to calls and, in some cases, an accident site emergency response team.

Fermentation is the method of producing some of the animal health products. Fermentation is usually not a hazardous process, as it involves growing a culture using a nutritional medium such as lard oil, glucose, or starch. Sometimes anhydrous ammonia is used for pH (acidity) control or as a nutrient, so the process can involve hazards. Solvents may be used to extract the active cells, but the quantities and the methodology are such that is can be done safely. Recycling these solvents is often part of the process.

PESTICIDES*

*Adapted from 3rd edition, Encyclopaedia of Occupational Health and Safety. Revision includes information from A. Baiinova, J.F. Copplestone, L.A. Dobrobolskij,  F. Kaloyanova-Simeonova, Y.I. Kundiev and A.M. Shenker.

The word pesticide generally denotes a chemical substance (which may be mixed with other substances) that is used for the destruction of an organism deemed to be detrimental to humans. The word clearly has a very wide meaning and includes a number of other terms, such as insecticides, fungicides, herbicides, rodenticides, bactericides, miticides, nematocides and molluscicides, which individually indicate the organisms or pests that the chemical or class of chemicals is designed to kill. As different types of chemical agents are used for these general classes, it is usually advisable to indicate the particular category of pesticide.

General Principles

Acute toxicity is measured by the LD50 value; this is a statistical estimate of the number of mg of the chemical per kg of body weight required to kill 50% of a large population of test animals. The dose may be administered by a number of routes, usually orally or dermally, and the rat is the standard test animal. Oral or dermal LD50 values are used according to which route has the lower value for a specific chemical. Other effects, either as a result of short-term exposure (such as neurotoxicity or mutagenicity) or of long-term exposure (such as carcinogenicity), have to be taken into account, but pesticides with such known properties are not registered for use. The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 1996-1997 issued by the World Health Organization (WHO) classifies technical products according to the acute risk to human health as follows:

·     Class IA—extremely hazardous

·     Class IB—highly hazardous

·     Class II—moderately hazardous

·     Class III—slightly hazardous.

The guidelines based on the WHO Classification list pesticides according to toxicity and physical state; these are presented in a separate article in this chapter.

Poisons enter the body through the mouth (ingestion), the lungs (inhalation), the intact skin (percutaneous absorption) or wounds in the skin (inoculation). The inhalation hazard is determined by the physical form and solubility of the chemical. The possibility and degree of percutaneous absorption varies with the chemical. Some chemicals also exert a direct action on the skin, causing dermatitis. Pesticides are applied in many different forms—as solids, by spraying in dilute or concentrated form, as dusts (fine or granulated), and as fogs and gases. The method of use has a bearing on the likelihood of absorption.

The chemical may be mixed with solids (often with food used as bait), water, kerosene, oils or organic solvents. Some of these diluents have some degree of toxicity of their own and may influence the rate of absorption of the pesticide chemical. Many formulations contain other chemicals which are not themselves pesticides but which enhance the effectiveness of the pesticide. Added surface-active agents are a case in point. When two or more pesticides are mixed in the same formulation, the action of one or both may be enhanced by the presence of the other. In many cases, the combined effects of mixtures have not been fully worked out, and it is a good rule that mixtures should always be treated as more toxic than any of the constituents on their own.

By their very nature and purpose, pesticides have adverse biological effects on at least some species, human beings included. The following discussion provides a broad overview of the mechanisms by which pesticides can act, and some of their toxic effects. Carcinogenicity, biological monitoring and safeguards in the use of pesticides are discussed in more detail elsewhere in this Encyclopaedia.

Organochlorine Pesticides

The organochlorine pesticides (OCPs) have caused intoxication following skin contact, ingestion or inhalation. Examples are endrin, aldrin and dieldrin. The rate of absorption and toxicity differ depending on the chemical structure and the solvents, surfactants and emulsifiers used in the formulation.

The elimination of OCPs from the body takes place slowly through the kidneys. Metabolism in the cells involves various mechanisms—oxidation, hydrolysis and others. OCPs have a strong tendency to penetrate cell membranes and to be stored in the body fat. Because of their attraction to fatty tissues (lipotropic properties) OCPs tend to be stored in the central nervous system (CNS), liver, kidneys and the myocardium. In these organs they cause damage to the function of important enzyme systems and disrupt the biochemical activity of the cells.

OCPs are highly lipophilic and tend to accumulate in fatty tissue as long as exposure persists. When exposure ceases, they are released slowly into the bloodstream, often over a period of many years, from whence they can be transported to other organs where genotoxic effects, including cancer, may be initiated. The great majority of US residents, for example, have detectable levels of organochlorine pesticides, including breakdown products of DDT, in their adipose (fatty) tissue, and the concentrations increase with age, reflecting lifetime accumulations.

A number of OCPs that have been used throughout the world as insecticides and herbicides are also proven or suspected carcinogens to humans. These are discussed in more detail in the Toxicology and Cancer chapters of this Encyclopaedia.

Acute intoxications

Aldrin, endrin, dieldrin and toxaphene are most frequently implicated in acute poisoning. Delay in the onset of symptoms in severely acute intoxications is about 30 minutes. With lower toxicity OCPs it is several hours but not more than twelve.

Intoxication is demonstrated by gastrointestinal symptoms: nausea, vomiting, diarrhoea and stomach pains. The basic syndrome is cerebral: headache, dizziness, ataxia and paraesthesia. Gradually tremors set in, starting from the eyelids and the face muscles, descending towards the whole body and the limbs; in severe cases this leads to fits of tonic-clonic convulsions, which gradually extend to the different muscle groups. Convulsions may be connected with elevated body temperature and unconsciousness and may result in death. In addition to the cerebral signs, acute intoxications may lead to bulbar paralysis of the respiratory and/or vasomotor centres, which causes acute respiratory deficiency or apnoea, and to severe collapse.

Many patients develop signs of toxic hepatitis and toxic nephropathy. After these symptoms have disappeared some patients develop signs of prolonged toxic polyneuritis, anaemia and haemorrhagic diathesis connected with the impaired thrombocytopoiesis. Typical of toxaphene is an allergic bronchopneumonia.

Acute intoxications with OCPs last up to 72 hours. When organ function has been seriously impaired, the illness may continue up to several weeks. Complications in cases of liver and kidney damage can be long-lasting.

Chronic poisoning

During the application of OCPs in agriculture as well as in their production, poisoning is most commonly chronic—that is, low doses of exposure over time. Acute intoxication (or high-level exposures at a particular instant) are less common and are usually the result of misuse or accidents, both in the home and in industry. Chronic intoxication is characterized by damage to the nervous, digestive and cardiovascular systems and the blood-formation process. All OCPs are CNS stimulants and are capable of producing convulsions, which frequently appear to be epileptic in character. Abnormal electroencephalographic (EEG) data have been recorded, such as irregular alpha rhythms and other abnormalities. In some cases bitemporal sharp-peaked waves with shifting localization, low voltage and diffuse theta activity have been observed. In other cases paroxysmal emissions have been registered, composed of slow sharp-peaked waves, sharp-peaked complexes and rhythmic peaks with low voltage.

Polyneuritis, encephalopolyneuritis and other nervous system effects have been described following occupational exposure to OCPs. Tremor of the limbs and alterations in the electromyograms (EMGs) have also been observed in workers. In workers handling OCPs such as BHC, polychloropinene, hexachlorobutadiene and dichloroethane, non-specific signs (e.g., diencephalic signs) have been observed and very often develop together with other signs of chronic intoxication. The most common signs of intoxication are headache, dizziness, numbness and tingling in the limbs, rapid changes in blood pressure and other signs of circulatory disturbances. Less frequently, colic pains below the right ribs and in the region of the umbilicus, and dyskinesia of the bile ducts, are observed. Behavioural changes, such as disturbances of sensory and equilibrium functions, are found. These symptoms are often reversible after cessation of the exposure.

OCPs cause liver and kidney damage. Microsomal enzyme induction has been observed, and increased ALF and aldolase activity have also been reported. Protein synthesis, lipoid synthesis, detoxification, excretion and liver functions are all affected. Reduction of creatinine clearance and phosphorus reabsorption are reported in workers exposed to pentachlorophenol, for example. Pentachlorophenol, along with the family of chlorophenols, are also considered possible human carcinogens (group 2B as classified by the International Agency for Research on Cancer (IARC)). Toxaphene is also considered to be a group 2B carcinogen.

Cardiovascular disturbances have been observed in exposed persons, most frequently demonstrated as dyspnoea, high heart rate, heaviness and pain in the heart region, increased heart volume and hollow heart tones.

Blood and capillary disturbances have also been reported following contact with OCPs. Thrombopenia, anaemia, pancytopenia, agranulocytosis, haemolysis and capillary disorders have all been reported. Medullar aplasia can be complete. The capillary damage (purpura) can develop following long- or short-term but intensive exposures. Eosinopenia, neutropenia with lymphocytosis, and hypochromic anaemia have been observed in workers subjected to prolonged exposures.

Skin irritation is reported to follow from skin contact with some OCPs, particularly chlorinated terpenes. Often chronic intoxications are clinically demonstrated by signs of allergic damage.

Organophosphate Pesticides

The organophosphorus pesticides are chemically related esters of phosphoric acid or certain of its derivatives. The organic phosphates are also identified by a common pharmacological property—the ability to inhibit the action of the cholinesterase enzymes.

Parathion is among the most dangerous of the organophosphates and is discussed in some detail here. In addition to parathion’s pharmacological effects, no insect is immune to its lethal action. Its physical and chemical properties have rendered it useful as an insecticide and acaricide for agricultural purposes. The description of parathion’s toxicity applies to other organophosphates, although their effects may be less rapid and extensive.

The toxic action of all organic phosphates is on the CNS through inhibition of the cholinesterase enzymes. Inhibiting these cholinesterases produces excessive and continuous stimulation of those muscle and gland structures which are activated by acetylcholine, to a point where life can no longer be sustained. Parathion is an indirect inhibitor because it must be converted in the environment or in vivo before it can effectively inhibit cholinesterase.

Organophosphates can generally enter the body by any route. Serious and even fatal poisoning may occur by ingesting a small amount of parathion while eating or smoking, for example. Organophosphates may be inhaled when dusts or volatile compounds are even briefly handled. Parathion is easily absorbed through the skin or the eye. The ability to penetrate the skin in fatal quantities without the warning of irritation makes parathion especially difficult to handle.

Signs and symptoms of organophosphate poisoning can be explained on the basis of cholinesterase inhibition. Early or mild poisoning may be hard to distinguish because of a number of other conditions; heat exhaustion, food poisoning, encephalitis, asthma and respiratory infections share some of the manifestations and confuse the diagnosis. Symptoms can be delayed for several hours after the last exposure but rarely longer than 12 hours. Symptoms most often appear in this order: headaches, fatigue, giddiness, nausea, sweating, blurred vision, tightness in the chest, abdominal cramps, vomiting and diarrhoea. In more advanced poisoning, difficult breathing, tremors, convulsions, collapse, coma, pulmonary oedema and respiratory failure follow. The more advanced the poisoning, the more obvious are the typical signs of cholinesterase inhibition, which are: pinpoint pupils; rapid, asthmatic type breathing; marked weakness; excessive sweating; excessive salivation; and pulmonary oedema.

In very severe parathion poisoning, in which the victim has been unconscious for some time, brain damage from anoxia may occur. Fatigue, ocular symptoms, electroencephalogram abnormalities, gastrointestinal complaints, excessive dreams and exposure intolerance to parathion have been reported to persist for days to months following acute poisoning. There is no evidence that permanent impairment occurs.

Chronic exposure to parathion may be cumulative in the sense that repeated exposures closely following each other can reduce cholinesterase faster than it can be regenerated, to the point where a very small exposure can precipitate acute poisoning. If the person is removed from exposure, clinical recovery is usually rapid and complete within a few days. The red blood cells and plasma should be tested for cholinesterase inhibition when phosphate ester poisoning is suspected. Red cell cholinesterase activity is most often reduced and close to zero in severe poisoning. Plasma cholinesterase is also severely reduced and is a more sensitive and more rapid indicator of exposure. There is no advantage in chemical determinations of parathion in the blood because metabolism of the pesticide is too rapid. However, p-nitrophenol, an end-product of the metabolism of parathion, can be determined in the urine. Chemical examination to identify the pesticide can be made on contaminated clothing or other material where contact is suspected.

Carbamates and Thiocarbamates

The biological activity of carbamates was discovered in 1923 when the structure of the alkaloid eserine (or physostigmine) contained in the seeds of Calabar beans was first described. In 1929 physostigmine analogues were synthesized, and soon such derivatives of dithiocarbamic acid as thiram and ziram were available. The study of carbamic compounds began in the same year, and now more than 1,000 carbamic acid derivatives are known. More than 50 of them are used as pesticides, herbicides, fungicides and nematocides. In 1947 the first carbamic acid derivatives having insecticide properties were synthesized. Some thiocarbamates have proved effective as vulcanization accelerators, and derivatives of dithiocarbamic acid have been obtained for the treatment of malignant tumours, hypoxia, neuropathies, radiation injuries and other diseases. Aryl esters of alkylcarbamic acid and alkyl esters of arylcarbamic acid are also used as pesticides.

Some carbamates can produce sensitization in exposed individuals, and a variety of foetotoxic, embryotoxic and mutagenic effects have also been observed for members of this family.

Chronic effects

The specific effects produced by acute poisoning have been described for each substance listed. A review of the specific effects gained from an analysis of published data makes it possible to distinguish similar features in the chronic action of the different carbamates. Some authors believe that the main toxic effect of carbamic acid esters is the involvement of the endocrine system. One of the peculiarities of carbamate poisoning is the possible allergic reaction of exposed subjects. The toxic effects of carbamates may not be immediate, which can present a potential hazard because of lack of warning. Results from animal experiments are indicative of embryotoxic, teratogenic, mutagenic and carcinogenic effects of some carbamates.

Baygon (isopropoxyphenyl-N-methylcarbamate) is produced by reaction of alkyl isocyanate with phenols, and is used as an insecticide. Baygon is a systemic poison. It causes inhibition of the serum cholinesterase activity up to 60% after oral administration of 0.75 to 1 mg/kg. This highly toxic substance exerts a weak effect on the skin.

Carbaryl is a systemic poison which produces moderately severe acute effects when ingested, inhaled or absorbed through the skin. It may cause local skin irritation. Being a cholinesterase inhibitor, it is much more active in insects than in mammals. Medical examinations of workers exposed to concentrations of 0.2 to 0.3 mg/m3 seldom reveal a fall in cholinesterase activity.

Betanal (3-(methoxycarbonyl)aminophenyl-N-(3-methylphenyl) carbamate; N-methylcarbanilate) belongs to the arylcarbamic acid alkyl esters and is used as a herbicide. Betanal is slightly toxic for the gastrointestinal and respiratory tracts. Its dermal toxicity and local irritation are insignificant.

Isoplan is a highly toxic member of the group, its action, like that of Sevin and others, being characterized by the inhibition of acetylcholinesterase activity. Isoplan is used as an insecticide. Pyrimor (5,6-dimethyl-2-dimethylamino-4-pyrimidinyl methylcarbamate) is a derivative of arylcarbamic acid alkyl esters. It is highly toxic for the gastrointestinal tract. Its general absorption and local irritative effect are not very pronounced.

Thiocarbamic Acid Esters

Ronite (sym-ethylcyclohexylethyl thiocarbamate; Eurex); Eptam (sym-ethyl-N,N-dipropyl thiocarbamate); and Tillam (sym-propyl-N-ethyl-N-butylthiocarbamate) are esters which are synthesized by reaction of alkylthiocarbamates with amines and of alkaline mercaptides with carbamoyl chlorides. They are effective herbicides of selective action.

The compounds of this group are slightly to moderately toxic, and the toxicity is reduced when they are absorbed through the skin. They can affect the oxidative processes as well as the nervous and endocrine systems.

Dithiocarbamates and bisdithiocarbamates include the following products, which have much in common as regards their use and their biological effects. Ziram is used as a vulcanization accelerator for synthetic rubbers and, in agriculture, as a fungicide and seed fumigant. This compound is very irritant to the conjunctiva and upper airway mucous membranes. It can cause extreme pain in the eyes, skin irritation and liver function disorders. It has embryotoxic and teratogenic effects. TTD is used as a seed fumigant, irritates the skin, causes dermatitis and affects the conjunctiva. It increases sensitivity to alcohol. Nabam is a plant fungicide and serves as an intermediate in the production of other pesticides. It is irritating to the skin and mucous membranes, and it is a narcotic in high concentrations. In the presence of alcohol it can cause violent vomiting. Ferbam is a fungicide of relatively low toxicity, but may cause renal function disorders. It irritates the conjunctiva, the mucous membranes of the nose and upper airways, and the skin. Zineb is an insecticide and fungicide that can cause irritation of the eyes, nose and larynx, and is harmful if inhaled or swallowed. Maneb is a fungicide that can cause irritation of the eyes, nose and larynx, and is harmful if inhaled or swallowed. Vapam (sodium methyldithiocarbamate; carbation) is white crystalline powder of unpleasant smell similar to that of carbon disulphide. It is an effective soil fumigant which destroys weed seeds, fungi and insects. It irritates the skin and mucous membranes.

Rodenticides

Rodenticides are toxic chemicals used for the control of rats, mice and other pest species of rodents. An effective rodenticide must conform to stringent criteria, a fact that is borne out by the small number of compounds that are currently in satisfactory use.

Poisoned baits are the most generally effective and widely used means of formulating rodenticides, but some are used as “contact” poisons (i.e., dusts, foams and gels), where the toxicant adheres to the fur of the animal and is ingested during subsequent grooming, while a few are applied as fumigants to burrows or infested premises. Rodenticides may conveniently be divided into two categories, depending on their mode of action: acute (single dose) poisons and chronic (multiple dose) poisons.

Acute poisons, such as zinc phosphide, norbormide, fluoracetamide, alpha-chloralose, are highly toxic compounds, with LD50s that are usually less than 100 mg/kg, and can cause death after a single dose consumed during a period not longer than a few hours.

Most acute rodenticides have the disadvantages of producing symptoms of poisoning rather quickly, of being generally rather non-specific, and lacking satisfactory antidotes. They are used at relatively high concentrations (0.1 to 10%) in bait.

Chronic poisons, which may act, for example, as anticoagulants (e.g., calciferol), are compounds that, having a cumulative mode of action, may need to be eaten by the prey over a succession of days to cause death. Anticoagulants have the advantage of producing symptoms of poisoning very late, usually well after the target species has eaten a lethal dose. An effective antidote to anticoagulants is available for those accidentally exposed. Chronic poisons are used at relatively low concentrations (0.002 to 0.1%).

Application

Rodenticides intended for use in baits are available in one or more of the following forms: technical grade material, concentrate (“master-mix”) or ready-to-use bait. Acute poisons are usually acquired as the technical material and mixed with the bait-base shortly before use. Chronic poisons, because they are used at low concentrations, are normally sold as concentrates, where the active ingredient is incorporated into a finely powdered flour (or talc) base.

When the final bait is prepared, the concentrate is added to the bait-base at the relevant rate. If the bait-base is of a coarse consistency, it may be necessary to add a vegetable or mineral oil at a prescribed rate to act as a “sticker”, thus ensuring that the poison adheres to the bait-base. It is commonly compulsory for a warning dye to be added to concentrates or ready-to-use baits.

In control treatments against rats and mice, poisoned baits are laid at frequent intervals throughout the infested area. When acute rodenticides are used, better results are obtained when unpoisoned bait (“prebait”) is laid for a few days before the poison is given. In “acute” treatments, poisoned bait is presented for a few days only. When anticoagulants are used, prebaiting is unnecessary, but the poison should remain in position for 3 to 6 weeks to achieve complete control.

Contact formulations of rodenticides are especially useful in situations where baiting is difficult for any reason, or where the rodents are not being drawn satisfactorily off their normal diet. The poison is usually incorporated in a finely divided powder (e.g., talc), which is laid on runways or around bait points, or is blown into burrows, wall cavities and so on. The compound may also be formulated in gels or foams, which are inserted into burrows.

The use of contact rodenticides relies on the target animal ingesting the poison while grooming itself. Because the amount of dust (or foam, etc.) adhering to the fur may be small, the concentration of the active ingredient in the formulation is usually relatively high, making it safe to use only where the contamination of food and so on cannot occur. Other specialized formulations of rodenticides include water baits and wax-impregnated blocks. The former, which are aqueous solutions of soluble compounds, are especially useful in dry environments. The latter are made by impregnating the toxicant and bait-base in molten paraffin wax (of low melting point) and casting the mixture into blocks. Wax-impregnated baits are designed to withstand wet climates and insect attack.

Hazards of rodenticides

Although toxicity levels of rodenticides may vary between target and non-target species, all poisons must be presumed to be potentially lethal to humans. Acute poisons are potentially more dangerous than chronic ones because they are rapid in action, non-specific and generally lack effective antidotes. Anticoagulants, on the other hand, are slow and cumulative, allowing adequate time for the administration of a reliable antidote, such as vitamin K.

As stated above, the concentrations of active ingredients in contact formulations of a given poison are higher than those in bait preparations, thus making operator hazard considerably greater. Fumigants present a special danger when used to treat infested premises, holds of ships and so on, and should be used only by trained technicians. The gassing of rodent burrows, although less hazardous, must also be carried out with extreme caution.

Herbicides

Grassy and broad-leaved weeds compete with crop plants for light, space, water and nutrients. They are hosts to bacteria, fungi and viruses, and hamper mechanical harvesting operations. Losses in crop yields as a result of weed infestation can be very heavy, commonly reaching 20 to 40%. Weed-control measures such as hand weeding and hoeing are ineffective in intensive farming. Chemical weedkillers or herbicides have successfully replaced mechanical methods of weed control.

In addition to their use in agriculture in cereals, meadows, open fields, pastures, fruit growing, greenhouses and forestry, herbicides are applied on industrial sites, railway tracks and power lines to remove vegetation. They are used for destroying weeds in canals, drainage channels and natural or artificial pools.

Herbicides are sprayed or dusted on weeds or on the soil they infest. They remain on the leaves (contact herbicides) or penetrate into the plant and so disturb its physiology (systemic herbicides). They are classified as non-selective (total—used to kill all vegetation) and selective (used to suppress the growth of or kill weeds without damaging the crop). Both non-selective and selective can be contact or systemic.

Selectivity is true when the herbicide applied in the correct dose and, at the right time, is active against certain species of weed only. An example of true selective herbicides are the chlorophenoxy compounds, which affect broad-leaved but not grassy plants. Selectivity can also be achieved by placement (i.e., by using the herbicide in such a way that it comes into contact with the weeds only). For example, paraquat is applied to orchard crops, where it is easy to avoid the foliage. Three types of selectivity are distinguished:

1.     physiological selectivity, which relies upon the plant’s ability to degrade the herbicide into non-phytotoxic components

2.     physical selectivity, which exploits the particular habit of the cultivated plant (e.g., the upright in cereals) and/or a specially fashioned surface (e.g., wax-coating, resistant cuticule) protecting the plant against herbicide penetration

3.  positional selectivity, in which the herbicide remains fixed in the upper soil layers adsorbed on colloidal soil particles and does not reach the root zone of the cultivated plant, or at least not in harmful quantities. Positional selectivity depends on the soil, precipitation and temperature as well as the water solubility and soil adsorption of the herbicide.

Some commonly used herbicides

Following are brief descriptions of acute and chronic effects associated with some commonly used herbicides.

Atrazine gives rise to decreased body weight, anaemia, disturbed protein and glucose metabolism in rats. It causes occupational contact dermatitis due to skin sensitization. It is considered a possible human carcinogen (IARC group 2B).

Barban, in repeated contact with 5% water emulsion, causes severe skin irritation in rabbits. It provokes skin sensitization in both experimental animals and agricultural workers, and causes anaemia, methaemoglobinaemia and changes in lipid and protein metabolism. Ataxia, tremor, cramps, bradycardia and ECG deviations are found in experimental animals.

Chlorpropharm can produce slight dermal irritation and penetration. In rats, exposure to atrazine causes anaemia, methaemoglobinaemia and reticulocytosis. Chronic application causes skin carcinoma in rats.

Cycloate causes polyneuropathia and liver damage in experimental animals. No clinical symptoms have been described after occupational exposure of workers for three consecutive days.

2,4-D poses moderate dermal toxicity and skin irritancy risks to exposed persons. It is highly irritating to the eyes. Acute exposures in workers provoke headache, dizziness, nausea, vomiting, raised temperature, low blood pressure, leucocytosis, and heart and liver injury. Chronic occupational exposure without protection may cause nausea, liver functional changes, contact toxic dermatitis, irritation of airways and eyes, as well as neurological changes. Some of the derivatives of 2,4-D are embryotoxic and teratogenic for experimental animals in high doses only.

2,4-D and the related phenoxy herbicide 2,4,5-T are rated as group 2B carcinogens (possible human carcinogens) by the IARC. Lymphatic cancers, particularly non-Hodgkin lymphoma (NHL), have been associated in Swedish agricultural workers with exposure to a commercial mixture of 2,4-D and 2,4,5-T (similar to the herbicide Agent Orange used by the US military in Viet Nam during the years 1965 to 1971). Possible carcinogenicity is often ascribed to contamination of 2,4,5-T with 2,3,7,8-tetrachloro-dibenzo-p-dioxin. However, a US National Cancer Institute research group reported a risk of 2.6 for adult NHL among Kansas residents exposed to 2,4-D alone, which is not thought to be dioxin-contaminated.

Dalapon-Na can cause depression, an unbalanced gait, decreased body weight, kidney and liver changes, thyroid and pituitary dysfunctions, and contact dermatitis in workers who are exposed. Diallate has dermal toxicity and causes irritation to the skin, eyes and mucous membranes. Diquat is an irritant to the skin, eyes and upper respiratory tract. It can cause a delay in the healing of cuts and wounds, gastrointestinal and respiratory disturbances, bilateral cataract and functional liver and kidney changes.

Dinoseb presents dangers because of its toxicity through dermal contact. It can cause moderate skin and pronounced eye irritation. The fatal dose for humans is about 1 to 3 g. After an acute exposure, Dinoseb causes central nervous system disturbances, vomiting, reddening (erythema) of the skin, sweating and high temperature. Chronic exposure without protection results in decreased weight, contact (toxic or allergic) dermatitis and gastrointestinal, liver and kidney disturbances. Dinoseb is not used in many countries because of its serious adverse effects.

Fluometuron is a moderate skin sensitizer in guinea-pigs and humans. It has been observed to cause decreased body weight, anaemia, and liver, spleen and thyroid gland disturbances. The biological action of diuron is similar.

Linuron causes mild irritation to the skin and eyes, and has low cumulative toxicity (threshold value after single inhalation 29 mg/m3). It causes CNS, liver, lung and kidney changes in experimental animals, as well as thyroid dysfunction.

MCPA is highly irritant to skin and mucous membranes, has low cumulative toxicity and is embryotoxic and teratogenic in high doses in rabbits and rats. Acute poisoning in humans (an estimated dose of 300 mg/kg) results in vomiting, diarrhoea, cyanosis, mucus burns, clonic spasms, and myocardium and liver injury. It provokes severe contact toxic dermatitis in workers. Chronic exposure without protection results in dizziness, nausea, vomiting, stomach aches, hypotonia, enlarged liver, myocardium dysfunction and contact dermatitis.

Molinate can reach a toxic concentration after single inhalation of 200 mg/m3 in rats. It causes liver, kidney and thyroid disturbances, and is gonadotoxic and teratogenic in rats. It is a moderate skin sensitizer in humans.

Monuron in high doses can result in liver, myocardium and kidney disturbances. It causes skin irritation and sensitization. Similar effects are shown by monolinuron, chloroxuron, chlortoluron and dodine.

Nitrofen is a strong skin and eye irritant. Chronic occupational exposure without protection results in CNS disturbances, anaemia, raised temperature, decreased body weight, fatigue and contact dermatitis. It is considered a possible human carcinogen (group 2B) by the IARC.

Paraquat has dermal toxicity and irritant effects on skin or mucous membranes. It causes nail damage and nose bleeding in occupational conditions without protection. Accidental oral poisoning with paraquat has resulted when it was left within reach of children or transferred from the original container into a bottle used for a beverage. Early manifestations of such intoxication are corrosive gastrointestinal effects, renal tubular damage and liver dysfunction. Death is due to circulatory collapse and progressive pulmonary damage (pulmonary oedema and haemorrhage, intra-alveolar and interstitial fibrosis with alveolitis and hyaline membranes), clinically revealed by dyspnoea, hypoxaemia, basal rales and roentgenographic evidence of infiltration and athelectasis. The renal failure is followed by lung damage, and accompanied in some cases by liver or myocardium disturbances. Mortality is higher with poisoning from liquid concentrate formulations (87.8%), and lower from granular forms (18.5%). The fatal dose is 6 g paraquat ion (equivalent to 30 ml Gramoxone or 4 packets of Weedol), and no survivors are reported at greater doses, irrespective of the time or vigour of treatment. Most survivors had ingested less than 1 g paraquat ion.

Potassium cyanate is associated with high inhalation and dermal toxicity in experimental animals and humans due to the metabolic conversion to cyanide, which is discussed elsewhere in this Encyclopaedia.

Prometryn exhibits moderate dermal toxicity and skin and eye irritation. It provokes decreased clotting and enzyme abnormalities in animals and has been found to be embryotoxic in rats. Exposed workers may complain of nausea and sore throat. Analogous effects are shown by propazine and desmetryne.

Propachlor’s toxicity is doubled at high environmental temperatures. Skin and mucous membrane irritation and mild skin allergy are associated with exposure. The toxic concentration after single inhalation is 18 mg/m3 in rats, and it is thought to exhibit moderate cumulative toxicity. Propachlor causes polyneuropathies; liver, myocardium and kidney disturbances; anaemia; and damage to testes in rats. During spraying from the air, the concentration in the spray cabin has been found to be about 0.2 to 0.6 mg/m3. Similar toxic properties are shown by propanil.

Propham exhibits moderate cumulative toxicity. It causes haemodynamic disturbances, and liver, lung and kidney changes are found in experimental animals.

Simazine causes slight irritation of the skin and mucous membranes. It is a moderate skin sensitizer in guinea-pigs. It also causes CNS, liver and kidney disturbances and has mutagenic effect in experimental animals. Workers may complain of weariness, dizziness, nausea and olfactory deviations after application without protective equipment.

2,4,5-T causes pronounced irritation and embryotoxic, teratogenic and carcinogenic effects in animals; there are also data on its gonadotoxic action in women. Because the extremely toxic chemical dioxin can be a contaminant of the trichlorophenoxy acids, use of 2,4,5-T is prohibited in many countries. Agricultural, forestry and industrial workers exposed to mixtures of 2,4-D and 2,4,5-T have been reported at increased risk for both soft-tissue sarcomas and non-Hodgkin lymphomas.

Trifluralin causes slight irritation of skin and mucous membranes. An increased incidence of liver carcinoma has been found in hybrid female mice, probably due to contamination with N-nitroso compounds. Trifluralin causes anaemia and liver, myocardium and kidney changes in experimental animals. Extensively exposed workers have developed contact dermatitis and photodermatitis.

Fungicides

Some fungi, such as rusts, mildews, moulds, smuts, storage rots and seedling blights, are able to infect and cause diseases in plants, animals and humans. Others can attack and destroy non-living materials such as wood and fibre products. Fungicides are used to prevent these diseases and are applied by spraying, dusting, seed dressing, seedling and soil sterilization, and fumigation of warehouses and greenhouses.

Fungi causing plant diseases can be arranged into four sub-groups, which differ by the microscopic characters of the mycelium, the spores and the organs on which the spores were developed:

1.     phycomycetes—soil-borne organisms causing club rot of brassicae, wart diseases of potatoes and so on

2.     ascomycetes—perithecia-forming powdery mildews and fungi causing apple scab, black currant leaf spot and rose black spot

3.     basidiomycetes, including loose smut of wheat and barley, and several rusts species

4.     fungi imperfecti, which includes the genera Aspergillus, Fusarium, Penicillium and so on, that are of great economic importance because they cause significant losses during plant growth, at harvest, and after harvest. (e.g., Fusarium species infect barley, oats and wheat; Penicillium species cause brown rot of pomaceous fruit).

Fungicides have been used for centuries. Copper and sulphur compounds were the first to be used, and Bordeaux mixture was applied in 1885 to vineyards. A great number of widely differing chemical compounds with fungicidal action are used in many countries.

Fungicides can be classified into two groups according to their mode of action: protective fungicides (applied at a time prior to the arrival of the fungal spores—e.g., sulphur and copper compounds) or eradicant fungicides (applied after the plant has become infected—e.g., mercury compounds and nitroderivatives of the phenols). The fungicides either act on the surface of the leaves and seeds or penetrate into the plant and exert their toxic action directly on the fungi (systemic fungicides). They can also alter the physiological and biochemical processes in the plant and thus produce artificial chemical immunization. Examples of this group are the antibiotics and the rodananilides.

Fungicides applied to seed act primarily against surface-borne spores. However, in some cases they are required to persist on the seed coat long enough to be effective against the dormant mycelium contained within the seed. When applied to the seed before sowing, the fungicide is called seed disinfectant or seed dressing, though the latter term may include treatment not intended to counter seed-borne fungi or soil pests. To protect wood, paper, leather and other materials, fungicides are used by impregnation or staining. Special drugs with fungicidal action are also used to control fungal diseases in humans and animals.

Specific field applications include:

·     Seed dressing. This is a simple and economically efficient method for the control of plant diseases. The pests are destroyed on the seeds and in the soil during the development of the seed. Despite the availability of efficient alternative compounds, the mercury fungicides are still used to a considerable extent for this purpose. Dithiocarbamates, and particularly thiuram, are widely used. Chloranil and dichlone of the quinone group, hexachlorobenzene, formaldehyde and some antibiotics are also used for seed dressing. The seeds can be treated by either the dry or the wet method.

·     Soil disinfection. This is a more general action, with fungicides incorporated into the soil as solid or liquid formulations that liberate volatile or easily soluble components (e.g., chloropicrin, methyl bromide, dibromomethane, formaldehyde, vapam, dazomet, allyl alcohol, pentachloronitrobenzene and chloroneb). These fungicides are used most intensively on greenhouse soil. Several of them are known or suspected carcinogens.

·     Application on plants. To control airborne diseases, fungicides are used on annual field crops, fruit trees and berry crops. Almost all fungicide groups are used for this purpose. Copper compounds, dithiocarbamates, aromatic nitro derivatives, quinones, phthalamides, guanidines and chlorinated hydrocarbons are the most frequently used; some heterocyclics, nickel compounds and some antibiotics are also used.

Hazards of fungicides

The fungicides cover a great variety of chemical compounds differing widely in their toxicity. Highly toxic compounds are used as fumigants of foods and warehouses, for seed dressing and for soil disinfection, and cases of poisoning have been described with organomercurials, hexachlorobenzene and pentachlorobenzene, as well as with the slightly toxic dithiocarbamates. These and several other chemicals are discussed in more detail elsewhere in this article, chapter and Encyclopaedia. Some are briefly reviewed here.

Chinomethionate has a high cumulative toxicity and inhibits thiol groups and some enzymes containing them; it lowers phagocytic activity and has antispermatogenic effects. It is irritant to the skin and the respiratory system. It can damage the CNS, the liver and the gastrointestinal tract. Glutathione and cysteine provide protection against the acute effects of chinomethionate.

Chloranil is irritating to the skin and the upper respiratory tract; it can also cause depression of the CNS and dystrophic changes in the liver and kidney. The biological monitoring of exposed persons has shown an increased level of the urinary phenols, both free and bound.

Dazomet is used also as a nematocide and a slimicide. This compound and its decomposition products are sensitizers and mild irritants of the eye, nose, mouth and skin. Poisoning is characterized by a variety of symptoms, including anxiety, tachycardia and quick breathing, hypersalivation, clonic cramps, impaired movement coordination, sometimes hyperglycaemia and cholinesterase inhibition. The main pathomorphological findings are enlargement of the liver and degenerative changes of the kidney and other internal organs.

Dichlofluanid inhibits thiol groups. In experimental animals it caused histological changes in liver, proximal tubules of the kidney and adrenal cortex, with the reduction of the lymphatic tissue in the spleen. It is a moderate irritant of the skin and mucous membranes.

Diclone, in addition to sharing the irritant and blood depressant properties common to quinones, is an experimental animal carcinogen.

Dinobuton, like dinitro-o-cresol (DNOC), disturbs cell metabolism by inhibiting oxidative phosphorylation, with the loss of energy-rich compounds such as adenosintriphosphoric acid (ATP). It can cause severe liver dystrophy and necrosis of the convoluted tubules of the kidneys. The clinical manifestations of the intoxication are high temperature, methaemoglobinaemia and haemolysis, nervous disturbances and irritation of the skin and mucous membranes.

Dinocap can increase the blood level of alkaline phosphatase and is a moderate irritant of the skin and mucous membranes. It produces distrophic changes in the liver and kidney, and hypertrophy of the myocardium. In acute poisoning, disturbances in thermoregulation, clonic cramps and breathing difficulties have been observed.

Hexachlorobenzene (HCB) is stored in the body fat. It interferes with porphyrin metabolism, increasing the urinary excretion of coproporphyrins and uroporphyrins; it increases also the levels of transaminases and dehydrogenases in the blood. It can produce liver injury (hepatomegaly and cirrhosis), photosensitization of the skin, a porphyria similar to porphyria cutanea tarda, arthritis and hirsutism (monkey disease). It is a skin irritant. Chronic poisoning needs long-term treatment, mainly symptomatic, and it is not always reversible on cessation of exposure. It is classified as a possible human carcinogen (group 2B) by the IARC.

Milneb can cause gastrointestinal disturbances, weakness, decrease of the body temperature and leukopoenia.

Nirit has haemotoxic properties and causes anaemia and leucocytosis with toxic granulation of the leucocytes, in addition to degenerative changes in the liver, spleen and kidneys.

Quinones, in general, cause blood disturbances (methaemoglobinaemia, anaemia), affect the liver, disturb vitamin metabolism, particularly that of ascorbic acid, and are irritant to the respiratory ways and the eye. Chloranil and dichlone are the quinone derivatives most widely used as fungicides.

Thiabendazole has caused thymus involution, colloid depletion in the thyroid and increase in liver and kidney size. It is also used as an anthelmintic in cattle.

Safety and Health Measures

Labelling and storage

The requirements regarding the labelling of pesticides laid down in national and international legislation should be strictly applied to both imported and locally produced chemicals. The label should give the following essential information: both the approved name and the trade name of the chemical; the name of the manufacturer, packager or supplier; the directions for use; the precautions to be taken during use, including details of protective equipment to be worn; the symptoms of poisoning; and the first-aid treatment for suspected poisoning.

The greater the degree of toxicity or hazard of the chemical, the more precise should be the wording on the label. It is sound practice for the different classes to be clearly distinguished by background colours on the label and, in the case of compounds of high or extreme hazard, for the appropriate danger symbol to be incorporated. It often occurs that an adequately labelled quantity of pesticide in bulk is locally repacked into smaller containers. Each such small package should bear a similar label, and repacking in containers which have held, or are easily identifiable with, containers used for food should be absolutely forbidden. If small packages are to be transported, the same rules apply as for the carriage of larger packages. (See the chapter Using, storing and transporting chemicals.)

Pesticides of moderate or higher hazard should be so stored that only authorized persons can have access to them. It is particularly important that children should be excluded from any contact with pesticide concentrates or residues. Spillages often occur in storage and repacking rooms, and they must be cleaned up with care. Rooms used only for storage should be soundly constructed and fitted with secure locks. Floors should be kept clear and the pesticides clearly identified. If repacking is carried out in storage rooms, adequate ventilation and light should be available; floors should be impervious and sound; washing facilities should be available; and eating, drinking and smoking should be prohibited in the area.

A few compounds react with other chemicals or with air, and this has to be taken into account when planning storage facilities. Examples are cyanide salts (which react with acid to produce hydrogen cyanide gas) and dichlorvos (which vaporizes in contact with air). (Dichlorvos is classified as a group 2B possible human carcinogen by the IARC.).

Mixing and application

Mixing and application may comprise the most hazardous phase of the use of pesticides, since the worker is exposed to the concentrate. In any particular situation, only selected persons should be responsible for mixing; they should be thoroughly conversant with the hazards and provided with the proper facilities for dealing with accidental contamination. Even when the mixed formulation is of such a toxicity that it can be used with a minimum of personal protective equipment (PPE), more elaborate equipment may need to be provided for and used by the mixer.

For pesticides of moderate or higher hazard, some type of PPE is almost always necessary. The choice of particular items of equipment will depend on the hazard of the pesticide and the physical form in which it is being handled. Any consideration of PPE must also include not only provision but also adequate cleaning, maintenance and replacement.

Where climatic conditions preclude the use of some types of PPE, three other principles of protection can be applied—protection by distance, protection by time and protection by change of working method. Protection by distance involves modification of the equipment used for application, so that the person is as far away as possible from the pesticide itself, bearing in mind the likely routes of absorption of a specific compound.

Protection by time involves limitation of hours of work. The suitability of this method depends on whether the pesticide is readily excreted or whether it is cumulative. Accumulation of some compounds occurs in the body when the rate of excretion is slower than the rate of absorption. With some other compounds, a cumulative effect may occur when the person is exposed to repeated small doses which, taken individually, may not give rise to symptoms.

Protection by change of working method involves a reconsideration of the whole operation. Pesticides differ from other industrial processes in that they can be applied from the ground or the air. Changes of method on the ground depend largely on the choice of equipment and the physical nature of the pesticide to be applied.

Pesticides that are applied from the air can be in the form of liquids, dusts or granules. Liquids may be sprayed from very low altitudes, frequently as fine droplets of concentrated formulations, known as ultra-low volume (ULV) applications. Drift is a problem particularly with liquids and dusts. Aerial application is an economical way of treating large tracts of land but entails special hazards to pilots and to workers on the ground. Pilots can be affected by leakage from hoppers, by pesticides carried into the cockpit on clothes and boots, and by flying back through the swathe just released or through the drift from the swathe. Even minor degrees of absorption of some pesticides or their local effects (such as may be caused, for instance, by an organophosphorus compound in the eye) can affect a pilot to the extent that he or she cannot maintain the high degree of vigilance necessary for low flying. Pilots should not be allowed to engage in pesticide operations unless they have been specially trained in the items listed above, in addition to any special aviation and agricultural operational requirements.

On the ground, loaders and flaggers may be affected. The same principles apply to loaders as to others dealing with pesticides in bulk. Flaggers mark the swathe to be flown and can be severely contaminated if the pilot misjudges the moment of release. Balloons or flags can be placed in position before or ahead of the operation, and workers should never be used as flaggers within the flight pattern.

Other restrictions

The hazards associated with pesticides do not end with their application; with the more toxic compounds it has been shown that there is a danger to workers entering a sprayed crop too soon after application. It is therefore important that all workers and members of the general public should be informed concerning the areas where a toxic pesticide has been applied and the earliest date on which it is safe to enter and work in these areas. Where a food crop has been sprayed, it is also important that the crop not be harvested until a sufficient period has elapsed for degradation of the pesticide to take place, in order to avoid excessive residues on food.

Disposal of pesticides and containers. Spillage of pesticides at any stage of their storage or handling should be treated with great care. Liquid formulations may be reduced to solid phase by evaporation. Dry sweeping of solids is always hazardous; in the factory environment, these should be removed by vacuum cleaning or by dissolving them in water or other solvent. In the field they may be washed away with water into a suitable soak-hole. Contaminated topsoil should be removed and buried if any domestic animals or fowls are in the area. Soak-holes should be used for disposing of washing waters from cleaning application equipment, clothing or hands. These should be at least 30 cm deep and sited well away from wells or watercourses.

Empty pesticide containers should be collected with care, or disposed of safely. Plastic liners, and paper or card containers should be crushed and buried well below the topsoil or burned, preferably in an incinerator. Metal containers of some pesticides can be decontaminated according to the instructions of the pesticide manufacturers. Such drums should be clearly marked “Not to be used for food or for water for drinking or domestic use”. Other metal containers should be punctured, crushed or buried.

Hygiene and first aid

Where a pesticide is of moderate or higher hazard and can be readily absorbed through the skin, special precautions are necessary. In some situations where workers may become accidentally contaminated with large quantities of concentrate, such as in factory situations and mixing, it is necessary to provide a shower bath in addition to the usual washing facilities. Special arrangements for cleaning clothing and overalls may be necessary; in any case, these should not be left for the worker to wash at home.

Since pesticides are often applied outside the factory environment, depending on the chemical used, special care may have to be taken to provide washing facilities at the workplace, even though this may be in remote fields. Workers must never bathe themselves in canals and rivers, the water from which may be subsequently used for other purposes; the washing water provided should be disposed of with care as outlined above. Smoking, eating and drinking before washing should be absolutely prohibited when any pesticide of moderate or higher toxicity is being handled or used.

Where an antidote exists which can be readily used as a first-aid measure for a specific pesticide (e.g., atropine for organophosphorus poisoning), it should be readily available to workers, who should be instructed in the method of its use. When any pesticide is being used on a substantial scale, medical personnel in the area should be informed by the persons responsible for distribution. The nature of the chemical used should be well defined so that medical facilities can be equipped and will know the specific antidotes, where these are applicable and how to recognize cases of poisoning. Facilities should also be available in order to make proper differential diagnosis, even if these are of the simplest type, such as test papers for determining cholinesterase levels. Strict routine medical supervision of workers heavily exposed to concentrates, as in the manufacture and packing of pesticides, is essential and should include laboratory tests and routine surveillance and record keeping.

Training

While all workers using pesticide formulations of moderate or higher hazard should be thoroughly trained in their use, such training is particularly important if the pesticide is extremely toxic. Training programmes must cover: toxicity of compounds used and routes of absorption; handling of concentrates and formulations; methods of use; cleaning of equipment; precautions to be taken and PPE to be worn; maintenance of PPE; avoidance of contamination of other crops, foods and water supplies; early symptoms of poisoning; and first-aid measures to be taken. All training should be strictly relevant to the pesticide actually being used, and, in the case of extremely hazardous compounds, it is wise to license operators following an examination to show that they have, in fact, a good understanding of the hazards and the procedures to be followed.

Public health measures

When pesticides are used, every effort must be made to avoid contamination of water supplies, whether these are officially recognized supplies or not. This not only concerns the actual application (when there may be immediate contamination) but must also include consideration of remote contamination by run-off through rainfall on recently treated areas. While pesticides in natural watercourses may be diluted to such a degree that the contaminated water may not be hazardous in itself, the effect on fish, on water vegetables used as food and grown in the watercourses, and on wild life as a whole must not be overlooked. Such hazards may be economic rather than directly related to health, but are no less important.

THE WHO GUIDELINES TO CLASSIFICATION OF PESTICIDES BY HAZARD*

*Adapted from WHO 1996.

Individual products are classified in a series of tables according to the products’ oral and dermal toxicity and physical states. Technical products classified as Class IA (extremely hazardous, Class IB (highly hazardous), Class II (moderately hazardous) and Class III (slightly hazardous) are listed in table 62.1, table 62.2, table 62.3 and table 62.4, respectively. Technical products unlikely to present any acute hazard in normal use are listed in table 62.5. The classification given in tables 62.1 to 62.5 is of technical compounds and only forms the starting point for the final classification of an actual formulation: the final classification of any product depends on its formulation. Classification of mixtures of pesticides is not included; many of these mixtures are marketed with varying concentrations of active constituents. (For information on how to find the hazard class of formulations and mixtures, see WHO 1996.) Technical products believed to be absolete or discontinued (see table 62.6) are not inclued in the Classification. Table 62.7  lists gaseous fumigants not included in the WHO Recommanded Classification of Pesticides by Hazard.

Table 62.1 List of technical products classified in Class IA: "Extremely hazardous"

Name

Status

Main use

Chemical type

Physical state

Route

LD50  (mg/kg)

Remarks

Acrolein

C

H

 

L

O

29

EHC 127; HSG 67

Alachlor

ISO

H

 

S

O

930

Adjusted classification; carcinogenic in rats and mice; DS 84

Aldicarb

ISO

I-S

C

S

O

0.93

DS 53; EHC 121; HSG 64

Arsenous oxide

C

R

 

S

O

180

Adjusted classification; minimum lethal dose   for humans of 2 mg/kg; evidence of   carcinogenicity for  humans is sufficient;  EHC 18; HSG 70

Brodifacoum

ISO

R

 

S

O

0.3

DS 57; EHC 175; HSG 93

Bromadialone

ISO

R

 

S

O

1.12

DS 88; EHC 175; HSG 94

Bromethalin

ISO

R

 

S

O

2

 

Calcium cyanide

C

FM

 

S

O

39

Adjusted classification; calcium cyanide is in Class IA as it   reacts with moisture to produce hydrogen cyanide gas;   the gas is not classified under the WHO system   (see table 62.7)

Captafol

ISO

F

 

S

O

5,000

Adjusted classification; carcinogenic in rats and mice;   HSG 49

Chlorfenvinphos

ISO

I

OP

L

O

10

 

Chlormephos

ISO

I

OP

L

O

7

 

Chlorophacinone

ISO

R

 

S

O

3.1

DS 62; EHC 175

Chlorthiophos

ISO

I

OP

L

O

9.1

 

Coumaphos

ISO

AC, MT

OP

L

O

7.1

 

CVP

N(J)

 

 

 

 

 

See chlorfenvinphos

Cycloheximide

ISO

F

 

S

O

2

 

DBCP

N(J)

 

 

 

 

 

See dibromochloropropane

Demephion-O and -S

ISO

I

OP

L

O

15

 

Demeton-O and -S

ISO

I

OP

L

O

2.5

DS 60

Dibromochloropropane

C

F-S

 

L

O

170

Adjusted classification; has been found to cause sterility in   humans and is mutagenic and carcinogenic in animals

Difenacoum

ISO

R

 

S

O

1.8

EHC 175; HSG 95

Difethialone

ISO

R

 

S

O

0.56

EHC 175

Difolatan

N(J)

 

 

 

 

 

See captafol

Dimefox

ISO

I

OP

L

O

1

Volatile

Diphacinone

ISO

R

 

S

O

2.3

EHC 175

Disulfoton

ISO

I

OP

L

O

2.6

DS 68

EPN

N(A,J)

I

OP

S

O

14

Has been reported as causing delayed neurotoxicity in hens

Ethoprop

N(A)

 

 

 

 

 

See ethoprophos

Ethoprophos

ISO

I-S

OP

L

D

26

DS 70

Ethylthiometon

N(J)

 

 

 

 

 

See disulfoton

Fenamiphos

ISO

N

OP

L

O

15

DS 92

Fensulfothion

ISO

I

OP

L

O

3.5

DS 44

Flocoumafen

N(B)

R

 

S

O

0.25

EHC 175

Fonofos

ISO

I-S

OP

L

O

c8

 

Hexachlorobenzene

ISO

FST

 

S

D

10,000

Adjusted classification; has caused a serious outbreak of   porphyria in humans; DS 26

Leptophos

ISO

I

OP

S

O

50

Adjusted classification; has been shown to cause delayed   neurotoxicity; DS 38

M74

N(J)

 

 

 

 

 

See disulfoton

MBCP

N(J)

 

 

 

 

 

See leptophos

Mephosfolan

ISO

I

OP

L

O

9

 

Mercuric chloride

ISO

F-S

 

S

O

1

 

Merkaptophos

N(U)

 

 

 

 

 

When mixed with merkaptophosteolovy,   see demeton -O and -S

Metaphos

N(U)

 

 

 

 

 

See parathion-methyl

Mevinphos

ISO

I

OP

L

D

4

DS 14

Nitrofen

ISO

H

 

S

O

c3,000

Adjusted classification; carcinogenic in rats and mice;   teratogenic in several species tested;   DS 84

Parathion

ISO

I

OP

L

O

13

DS 6; HSG 74

Parathion-methyl

ISO

I

OP

L

O

14

DS 7; EHC 145; HSG 75

Phenylmercury acetate

ISO

FST

 

S

O

24

Adjusted classification; highly toxic to mammals and very   small doses have produced renal lesions;   teratogenic in the rat

Phorate

ISO

I

OP

L

O

2

DS 75

Phosfolan

ISO

I

OP

L

O

9

 

Phosphamidon

ISO

I

OP

L

O

7

DS 74

Prothoate

ISO

AC,I

OP

L

O

8

 

Red squill

 

 

 

 

 

 

See scilliroside

Schradan

ISO

I

OP

L

O

9

 

Scilliroside

C

R

 

S

O

c0.5

Induces vomiting in mammals

Sodium fluoroacetate

C

R

 

S

O

0.2

DS 16

Sulfotep

ISO

I

OP

L

O

5

 

TEPP

ISO

AC

OP

L

O

1.1

 

Terbufos

ISO

I-S

OP

L

O

c2

 

Thiofos

N(U)

 

 

 

 

 

See parathion

Thionazin

ISO

N

OP

L

O

11

 

Timet

N(U)

 

 

 

 

 

See phorate

Source: WHO 1996.

Table 62.2 List of technical products classified in Class IB: "Highly hazardous"

Name

Status

Main use

Chemical type

Physical state

Route

LD50  (mg/kg)

Remarks

Aldoxycarb

ISO

I,N

C

S

O

27

 

Aldrin

ISO

I

OC

S

D

98

DS41; EHC 91; HSG 21

Allyl alcohol

C

H

 

L

O

64

Highly irritant to skin and eyes

Aminocarb

ISO

I

C

S

O

50

 

Antu

ISO

R

 

S

O

8

Induces vomiting in dogs. Some impurities are carcinogenic

Azinphos-ethyl

ISO

I

OP

S

O

12

DS 72

Azinphos-methyl

ISO

I

OP

S

O

16

DS 59

Benfuracarb

N(B)

I

C

L

O

138

 

Bis(tributyltin) oxide

C

F,M

 

L

O

194

Irritant to skin. DS 65; EHC 15

Blasticidin-S

N(J)

F

 

S

O

16

 

Bromophos-ethyl

ISO

I

OP

L

O

71

 

Butocarboxim

ISO

I

C

L

O

158

 

Butoxycarboxim

ISO

I

C

L

D

288

 

Cadusafos

ISO

N,I

OP

L

O

37

 

Calcium arsenate

C

I

 

S

O

20

 

Carbofuran

ISO

I

C

S

O

8

DS 56

Carbophenothion

ISO

I

OP

L

O

32

 

3-chloro-1,2-propanediol

C

R

 

L

O

112

In non-lethal dosage is a sterilant for male rats

Coumachlor

ISO

R

 

S

D

33

 

Coumatetralyl

ISO

R

 

S

O

16

 

Crotoxyphos

ISO

I

OP

L

O

74

 

zeta-Cypermethrin

ISO

I

PY

L

O

c86

 

DDVF

N(U)

 

 

 

 

 

See dichlorvos

DDVP

N(J)

 

 

 

 

 

See dichlorvos

Delnav

N(U)

 

 

 

 

 

See dioxathion

Demeton-S-methyl

ISO

I

OP

L

O

40

DS 61

Demeton-S-methylsulphon

ISO

I

OP

S

O

37

 

Dichlorvos

ISO

I

OP

L

O

56

Volatile, DS 2; EHC 79; HSG 18

Dicrotophos

ISO

I

OP

L

O

22

 

Dieldrin

ISO

I

OC

S

O

37

DS 17: EHC 91

Dimetilan

N(A,B)

I

C

S

O

47

 

Dinoseb

ISO

H

CNP

L

O

58

 

Dinoseb acetate

ISO

H

CNP

L

O

60

 

Dinoterb

ISO

H

CNP

S

O

25

 

Dioxathion

ISO

I

OP

L

O

23

 

DMTP

N(J)

 

 

 

 

 

See methidathion

DNBP

N(J)

 

 

 

 

 

See dinoseb

DNBPA

N(J)

 

 

 

 

 

See dinoseb acetate

DNOC

ISO

I-S,H

CNP

S

O

25

 

EDDP

N(J)

 

 

 

 

 

See edifenfos

Edifenphos

ISO

F

OP

L

O

150

 

Endrin

ISO

I

OC

S

O

7

DS 1; EHC 130; HSG 60

ESP

N(J)

I

OP

L

O

105

 

Famphur

N(A)

I

OP

S

O

48

 

Flucythrinate

ISO

I

PY

L

O

c67

Irritant to skin and eyes

Fluoroacetamide

C

R

 

S

O

13

 

Formetanate

ISO

AC

C

S

O

21

 

Fosmethilan

ISO

I

OP

S

O

49

Irritant to skin and eyes.

Furathiocarb

N(B)

I-S

C

L

O

42

 

Heptenophos

ISO

I

OP

L

O

96

 

Isazofos

ISO

I-S

OP

L

O

60

 

Isofenphos

ISO

I

OP

oil

O

28

 

Isothioate

ISO

I

OP

L

O

150

 

Isoxathion

ISO

I

OP

L

O

112

 

Lead arsenate

C

L

 

S

O

c10

 

Mecarbam

ISO

I

C

oil

O

36

 

Mercuric oxide

ISO

O

 

S

O

18

 

Methamidophos

ISO

I

OP

L

O

30

HSG 79

Methidathion

ISO

I

OP

L

O

25

 

Methomyl

ISO

I

C

S

O

17

DS 55, EHC 178; HSG 97

Methyl-merkapto-phosteolovy

N(U)

 

 

 

 

 

See demeton-S-methyl

Metilmerkapto-phosoksid

N(U)

 

 

 

 

 

See oxydemeton-methyl

Metriltriazotion

N(U)

 

 

 

 

 

See azinphos-methyl

Monocrotophos

ISO

I

OP

S

O

14

HSG 80

MPP

N(J)

 

 

 

 

 

See fenthion

Nicotine

ISO

 

 

L

D

50

 

Omethoate

ISO

I

OP

L

O

50

 

Oxamyl

ISO

I

C

S

O

6

DS 54

Oxydemeton-methyl

ISO

I

OP

L

O

65

 

Oxydeprofos

N(B)

 

 

 

 

 

See ESP

Paris green

C

L

 

S

O

22

Copper-arsenic complex

Pentachlorophenol

ISO

I,F,H

CNP

S

D

80

Irritant to skin; EHC 71; HSG 19

Phenylmercury nitrate

C

FST

OM

S

 

 

Oral LD50 not available, rat i.v. LD50 is 27 mg/kg

Pirimiphos-ethyl

ISO

I

OP

L

O

140

 

Propaphos

N(J)

I

OP

L

O

70

 

Propetamphos

ISO

I

OP

L

O

106

 

Sodium arsenite

C

R

 

S

O

10

 

Sodium cyanide

C

R

 

S

O

6

 

Strychnine

C

R

 

S

O

16

 

TBTO

 

 

 

 

 

 

See bis-(tributyltin) oxide

Tefluthrin

N(B)

I-S

PY

S

O

c22

 

Thallium sulfate

C

R

 

S

O

11

DS 10

Thiofanox

ISO

I-S

C

S

O

8

 

Thiometon

ISO

I

OP

oil

O

120

DS 67

Thioxamyl

 

 

 

 

 

 

See oxyamyl

Triamiphos

ISO

F

 

S

O

20

 

Triazophos

ISO

I

OP

L

O

82

 

Triazotion

N(U)

 

 

 

 

 

See azinphos-ethyl

Vamidothion

ISO

I

OP

L

O

103

 

Warfarin

ISO

R

 

S

O

10

DS 35, EHC 175; HSG 96

Zinc phosphide

C

R

 

S

O

45

DS 24, EHC 73

Source WHO 1996.

Table 62.3 List of technical products classified in Class II: "Moderately hazardous"

Name

Status

Main use

Chemical  type

Physical  state

Route

LD50  (mg/kg)

Remarks

Alanycarb

ISO

I

C

S

O

330

 

Allidochlor

ISO

H

 

L

O

700

Irritant to skin and eyes

Anilofos

ISO

H

 

S

O

472

 

Azaconazole

N(B)

F

 

S

O

308

 

Azocyclotin

ISO

AC

OT

S

O

80

 

Bendiocarb

ISO

I

C

S

O

55

DS 52

Bensulide

ISO

H

 

L

O

270

 

Benzofos

N(U)

 

 

 

 

 

See phosalone

BHC

ISO

 

 

 

 

 

See HCH

gamma-BHC

 

 

 

 

 

 

See gamma-HCH

Bifenthrin

N(B)

I

PY

S

O

c55

 

Bilanafos

ISO

H

 

S

O

268

 

Binapacryl

ISO

AC

 

S

O

421

 

Bioallethrin

C

I

PY

L

O

c700

Bioallethrin, esbiothrin, esbiol and esdepalléthrine are   members of the allethrin series; their toxicity varies   considerably within this series according to   concentrations of isomers.

Bisthiosemi

N(J)

R

 

S

O

c150

Induces vomiting in non-rodents

BPMC

 

 

 

 

 

 

See fenobucarb

Bromoxynil

ISO

H

 

S

O

190

 

Bronopol

N(B)

B

 

S

O

254

 

Bufencarb

ISO

I

C

S

O

87

 

Butamifos

ISO

H

 

L

O

630

 

Butenachlor

ISO

H

 

L

O

1,630

 

Butylamine

ISO

F

 

L

O

380

Irritant to skin

Camphechlor

ISO

I

OC

S

O

80

DS 20; EHC 45

Carbaryl

ISO

I

C

S

O

c300

DS 3; EHC 153; HSG 78

Carbosulfan

ISO

I

 

L

O

250

 

Cartap

ISO

I

 

S

O

325

 

Chloralose

C

R

 

S

O

400

 

Chlordane

ISO

I

OC

L

O

460

DS 36; EHC 34; HSG 13

Chlordimeform

ISO

AC

OC

S

O

340

 

Chlorphenamidine

N(J)

 

 

 

 

 

See chlordimeform

Chlorphonium

ISO

PGR

 

S

O

178

Irritant to skin and eyes

Chlorpyrifos

ISO

I

OP

S

O

135

DS 18

Clomazone

ISO

H

 

L

O

1,369

 

Copper sulfate

C

F

 

S

O

300

 

Cuprous oxide

C

F

 

S

O

470

 

Cyanazine

ISO

H

T

S

O

288

 

Cyanofenphos

ISO

I

OP

S

O

89

Has been reported as causing delayed neurotoxicity   in hens; no longer manufactured

Cyanophos

ISO

I

OP

L

O

610

 

CYAP

N(J)

 

 

 

 

 

See cyanophos

Cyfluthrin

ISO

I

PY

S

O

c250

 

beta-Cyfluthrin

ISO

I

PY

S

O

450

 

Cyhalothrin

ISO

Ix

PY

oil

O

c144

EHC 99

lambda-Cyhalothrin

N(B)

I

PY

S

O

c56

EHC 142; HSG 38

CYP

N(J)

 

 

 

 

 

See cyanofenphos

Cypermethrin

ISO

I

PY

S

O

c250

DS 58; EHC 82; HSG 22

alpha-Cypermethrin

ISO

I

PY

S

O

c79

EHC 142

beta-Cypermethrin

ISO

I

PY

S

O

166

 

Cyphenothrin ((1R)-isomers)

ISO

I

PY

L

O

318

 

Cyprofuram

ISO

F

 

S

O

174

 

2,4-D

ISO

H

PA

S

O

375

DS 37; EHC 29; EHC 84

DAPA

N(J)

 

 

 

 

 

See fenaminosulf

DDT

ISO

I

OC

S

O

113

DS 21; EHC 9; EHC 83

Deltamethrin

ISO

I

PY

S

O

c135

DS 50; EHC 97; HSG 30

Dialifor

N(A,J)

 

 

 

 

 

See dialifos

Dialifos

ISO

I

OP

S

D

145

 

Di-allate

ISO

H

TC

L

O

395

 

Diazinon

ISO

I

OP

L

O

300

DS 45

Dibrom

N (Denmark)

 

 

 

 

 

See naled

Dichlofenthion

ISO

I-S

OP

L

O

270

 

Difenzoquat

ISO

H

 

S

O

470

 

Dimethoate

ISO

I

OP

S

O

c150

DS 42; EHC 90; HSG 20

Dinobuton

ISO

AC,F

 

S

O

140

 

Dioxabenzophos

N(B)

I

OP

S

O

125

 

Dioxacarb

ISO

I

C

S

O

90

 

Diquat

ISO

H

P

S

O

231

Irritant to skin, and eyes, and damages nails; DS 40; EHC 39; HSG 52

Drazoxolon

(ISO)

FST

 

S

O

126

 

ECP

N(J)

 

 

 

 

 

See dichlofenthion

Endosulfan

ISO

I

OC

S

O

80

DS 15; EHC 40; HSG 17

Endothal-sodium

(ISO)

H

 

S

O

51

 

EPBP

N(J)

I-S

OP

oil

O

275

 

EPTC

ISO

H

TC

L

O

1,652

 

Esbiol

 

 

 

 

 

 

See bioallethrin

Esbiothrin

 

 

 

 

 

 

See bioallethrin

Esdepalléthrine

 

 

 

 

 

 

See bioallethrin

Esfenvalerate

ISO

I

PY

S

O

87

 

Ethiofencarb

ISO

I

C

L

O

411

 

Ethion

ISO

I

OP

L

O

208

 

Etrimfos

ISO

I

OP

L

O

1,800

 

Fenaminosulf

ISO

F-S

 

S

O

60

 

Fenazaquin

ISO

AC

 

S

O

134

 

Fenchlorphos

ISO

I

OP

L

O

1,740

DS 69

Fenitrothion

ISO

I

OP

L

O

503

DS 30; EHC 133; HSG 65

Fenobucarb

N(B)

I

C

S

O

620

 

Fenpropathrin

ISO

I

PY

S

O

c66

 

Fenthion

ISO

I,L

OP

L

D

586

DS 23

Fentin acetate

(ISO)

F

OT

S

O

125

DS 22

Fentin hydroxide

(ISO)

F

OT

S

O

108

DS 22

Fenvalerate

ISO

I

PY

L

O

c450

EHC 95, DS 90; HSG 34

Fipronil

N(B)

I

Pyrazole

S

O

92

 

Fluvalinate

N(B)

I

 

oil

O

282

Irritant to skin

Fluxofenim

ISO

H

 

oil

O

670

 

Formothion

ISO

I

OP

L

O

365

 

Fosfamid

N(U)

 

 

 

 

 

See dimethoate

Furconazole-cis

ISO

F

 

S

O

450

 

Guazatine

N(B)

FST

 

S

O

230

LD50 value refers to triacetate

Haloxyfop

N(A,B)

H

 

S

O

393

 

HCH

ISO

I

OC

S

O

100

The LD50 varies according to the mixture of isomers.   The value shown has been chosen, and the technical   product placed in Class II, as a result of the cumulative   properties of the beta isomer

Gamma-HCH

ISO

I

OC

S

O

88

DS 12; EHC 124; HSG 54

Heptachlor

ISO

I

OC

S

O

100

DS 19; EHC 38; HSG 14

Imazalil

ISO

F

 

S

0

320

 

Imidacloprid

N(B)

I

Nitro- guanidine

S

O

450

 

Iminoctadine

ISO

F

 

S

O

300

Eye irritant

Ioxynil

ISO

H

 

S

O

110

 

Ioxynil octanoate

(ISO)

H

 

S

O

390

 

Isoprocarb

ISO

I

C

S

O

403

 

Karbation

N(U)

 

 

 

 

 

See metam-sodium

Lindane

ISO

 

 

 

 

 

See gamma-HCH

MEP

N(J)

 

 

 

 

 

See fenitrothion

Mercaptodimethur

 

 

 

 

 

 

See methiocarb

Mercurous chloride

C

F

 

S

O

210

 

Metaldehide

ISO

M

 

S

O

227

 

Metam-sodium

(ISO)

F-S

 

S

O

285

 

Methacrifos

ISO

I

OP

L

O

678

 

Methasulfocarb

ISO

F

 

S

O

112

 

Methiocarb

ISO

I

C

S

O

100

 

Methyl isothiocyanate

ISO

F-S

 

S

O

72

Skin and eye irritant

Metolcarb

ISO

I

C

S

O

268

 

MICP

N(J)

 

 

 

 

 

See isoprocarb

Molinate

ISO

H

TC

L

O

720

 

MPMC

 

 

 

 

 

 

See xylylcarb

Nabam

ISO

F

TC

S

O

395

Goitrogenic in rats

NAC

N(J)

 

 

 

 

 

See carbaryl

Naled

ISO

I

OP

L

O

430

DS 39

Norbormide

ISO

R

 

S

O

52

 

2,4-PA

N(J)

 

 

 

 

 

See 2,4-D

PAP

N(J)

 

 

 

 

 

See phenthoate

Paraquat

ISO

H

P

S

O

150

Has serious delayed effects if absorbed; is relatively   low hazard in actual use but is dangerous if   accidentally taken orally; DS 4; EHC 39; HSG 51

Pebulate

ISO

H

TC

L

O

1,120

 

Permethrin

ISO

I

PY

L

O

c500

DS 51; EHC 94; HSG 33

PHC

N(J)

 

 

 

 

 

See propoxur

Phenthoate

ISO

I

OP

L

O

c400

DS 48

Phosalone

ISO

I

OP

L

O

120

 

Phosmet

ISO

I,AC

OP

S

O

230

 

Phoxim

ISO

I

OP

L

D

1,975

DS 31

Phthalofos

N(U)

 

 

 

 

 

See phosmet

Pindone

ISO

R

 

S

O

50

 

Piperophos

ISO

H

 

oil

O

324

 

Pirimicarb

ISO

AP

C

S

O

147

 

Polychlorcamphene

N(U)

 

 

 

 

 

See camphechlor

Prallethrin

ISO

I

PY

oil

O

460

 

Profenofos

ISO

I

OP

L

O

358

 

Promacyl

N(Aust)

Ix

C

L

O

1,220

 

Promecarb

ISO

I

C

S

O

74

 

Propiconazole

ISO

F

 

L

O

1,520

 

Propoxur

ISO

I

C

S

O  

95

DS 25

Prosulfocarb

ISO

H

 

L

O

1,820

 

Prothiofos

ISO

I

OP

L

O

925

 

Prothiophos

 

 

 

 

 

 

See prothiofos

Pyraclofos

N(B)

I

OP

L

O

237

 

Pyrazophos

ISO

F

 

S

O

435

 

Pyrethrins

C

I

 

L

O

500-1,000

Mixture of compounds present in Pyrethrum,  Cineraefolium  and  other  flowers; DS 11

Pyroquilon

ISO

F

 

S

O

320

 

Quinalphos

ISO

I

OP

S

O

62

 

Quizalofop-p-tefuryl

ISO

H

 

L

O

1,012

 

Reglon

N(U)

 

 

 

 

 

See diquat

Ronnel

N(A)

 

 

 

 

 

See fenchlorphos

Rotenone

C

I

 

S

O

132-1,500

Compounds from roots of Derris and   Lonchocarpus spp.; HSG 73

Salithion

 

 

 

 

 

 

See dioxabenzofos

SAP

N(J)

 

 

 

 

 

See bensulide

Sec-butylamine

 

 

 

 

 

 

See butylamine

Sevin

N(U)

 

 

 

 

 

See carbaryl

Sodium fluoride

ISO

I

 

S

O

180

 

Sodium hexafluorosilicate

ISO

L-S

 

S

O

125

 

Sulfallate

ISO

H

 

oil

0

850

Irritant to skin and eyes

Sulprofos

ISO

I

OP

oil

O

130

 

2,4,5-T

ISO

H

 

S

O

500

May contain a contaminant TCDD which affects   toxicity: it should not exceed 0.01 mg/kg technical   material; DS 13

TCA

ISO

 

 

 

 

 

The data shown refer to sodium trichloroacetic acid.

In many countries, the term TCA refers to the free acid   (now accepted by ISO); this is a solid with an oral LD50    of 400 mg/kg and if used as a pesticide is placed in   Class II. It is highly corrosive to skin.

Terbumeton

ISO

H

T

S

O

483

 

Tetraconazole

ISO

F

 

oil

O

1,031

 

Thiazafluron

ISO

H

 

S

O

278

 

Thiazfluron

N(B)

 

 

 

 

 

See thiazafluron

Thicyofen

ISO

F

 

S

O

368

 

Thiobencarb

ISO

H

TC

L

O

1,300

 

Thiocyclam

ISO

I

 

S

O

310

 

Thiodan

N(U)

 

 

 

 

 

See endosulfan

Thiodicarb

ISO

I

 

S

O

66

 

Tolyl-methyl-carbamate

 

 

 

 

 

 

See metolcarb

Toxaphene

N(A)

 

 

 

 

 

See camphechlor

Tralomethrin

N(B)

I

PY

S

O

c85

 

Trichloroacetic acid

 

 

 

 

 

 

 

Tricyclazole

ISO

F

 

S

O

305

 

Tridemorph

ISO

F

 

oil

O

650

 

Vernolate

ISO

H

TC

L

O

1,780

 

Xylylcarb

N(B)

I

C

S

O

380

 

Source: WHO 1996.

Table 62.4 List of technical products classified in Class III: "Slightly hazardous"

Name

Status

Main use

Chemical  type

Physical  state

Route

LD50  (mg/kg)

Remarks

Acephate

ISO

I

OP

S

O

945

 

Acetochlor

ISO

H

 

L

O

2,950

 

Acifluorfen

ISO

H

 

S

O

1,370

Strong irritant to eyes

Allethrin

ISO

I

PY

oil

O

c685

EHC 87; HSG 24

Ametryn

ISO

H

T

S

O

1,110

 

Amitraz

ISO

AC

 

S

O

800

 

Azamethiphos

ISO

I

OP

S

O

1,010

 

Azidithion

N(F)

 

 

 

 

 

See menazon

Barban

ISO

H

 

S

O

1,300

 

Bensultap

ISO

I

 

S

O

1,100

 

Bentazone

ISO

H

 

S

O

1,100

 

Benzoylprop-ethyl

(ISO)

H

 

S

O

1,555

 

Benzthiazuron

ISO

H

 

S

O

1,280

 

Bromofenoxim

ISO

H

 

S

O

1,217

 

Bromophos

ISO

I

OP

S

O

c1,600

DS 76

Buthidazole

ISO

H

 

S

O

1,480

 

Cacodylic acid

 

 

 

 

 

 

See dimethylarsinic acid

Carbofos

N(U)

 

 

 

 

 

See malathion

Chlorfenac

ISO

H

OC

S

O

575

 

Chlorfenethol

ISO

AC

OC

S

O

930

 

Chlorfenson

ISO

AC

OC

S

O

c2,000

Irritant to skin

Chlorinat

N(U)

 

 

 

 

 

See barban

Chlormequat (chloride)

ISO

PGR

 

S

O

670

 

Chloroacetic acid

C

H

 

S

O

650

Irritant to skin and eyes; data refer to sodium salt

Chlorobenzilate

ISO

AC

OC

S

O

700

 

Chlorocholine chloride

C

 

 

 

 

 

See chlormequat

Chlorthiamid

ISO

H

 

S

O  

757

 

Cismethrin

ISO

 

 

 

 

 

Resmethrin is a mixture of isomers, the   trans isomer (70-80%) being also known as   bioresmethrin and the cis isomer (20-30%) as   cismethrin. Bioresmethrin (see table 62.5) alone   is of much lower toxicity (oral LD50 9,000 mg/kg)

(DS 34)

Citrex

N(U)

 

 

 

 

 

See dodine

Clofop

ISO

H

 

L

O

1,208

 

Copper hydroxide

C

F

 

S

O

1,000

 

Copper oxychloride

C

F

 

S

O

1,440

 

4-CPA

ISO

PGR

 

S

O

850

 

Crufomate

ISO

I

OP

S

O

770

 

Cycloate

ISO

H

TC

L

O

+2,000

 

Cyhexatin

ISO

AC

OT

S

O

540

 

Cymoxanil

ISO

F

 

S

O

1,196

 

Cyproconazole

N(B)

F

 

S

O

1,020

 

Dazomet

ISO

F-S

 

S

O

640

Irritant to skin and eyes

2,4-DB

N(B)

H

 

S

O

700

 

DCBN

N(J)

 

 

 

 

 

See chlorthiamid

Deet

 

 

 

 

 

 

See diethyltoluamide

Dehydroacetic acid

C

F

 

S

O

1,000

 

2,4-DES

N(B,U)

 

 

 

 

 

See disul

Desmetryn

ISO

H

T

S

O

1,390

 

Diallyl dichloroacetamide

 

 

 

 

 

 

See dichlormid

Dicamba

ISO

H

 

S

O

1,707

 

Dichlone

ISO

FST

 

S

O

1,300

 

Dichlormid

N(A)

H

 

L

O

2,080

 

Dichlorobenzene

C

FM

 

S

O

500-5,000

Mixture of isomers

Dichlorophen

ISO

F

OC

S

O

1,250

 

Dichlorprop

ISO

H

 

S

O

800

 

Diclofop

ISO

H

 

S

O

565

 

Dicofol

ISO

AC

 

S

O

c690

DS 81

Dienochlor

ISO

AC

 

S

O

3,160

Acutely toxic by inhalation; skin sensitizer

Diethyltoluamide

ISO

RP (insect)

 

L

O

c2,000

DS 80

Difenoconazole

ISO

F

T

S

O

1,453

 

Dimepiperate

ISO

H

TC

S

O

946

 

Dimethachlor

ISO

H

 

S

O

1,600

 

Dimethametryn

ISO

H

T

L

O

3,000

 

Dimethipin

ISO

H

 

S

O

1,180

 

Dimethylarsinic acid

C

H

 

S

O

1,350

 

Diniconazole

ISO

F

 

S

O

639

 

Dinocap

ISO

AC,F

CNP

S

O

980

 

Diphenamid

ISO

H

 

S

O

970

 

Disul

ISO

H

 

S

O

730

 

Dithianon

ISO

F

 

S

O

640

 

2,4-DP

N(U)

 

 

 

 

 

See dichlorprop

Dodine

ISO

F

 

S

O

1,000

 

Doguadine

N(F)

 

 

 

 

 

See dodine

DSMA

 

 

 

 

 

 

See methylarsonic acid

Empenthrin ((1R) isomers)

ISO

I

PY

oil

O

+2,280

 

Ephirsulphonate

N(U)

 

 

 

 

 

See chlorfenson

Esprocarb

ISO

H

TC

L

O

+2,000

Skin and eye irritant

Etacelasil

ISO

PGR

 

L

O

2,065

 

Etaconazole

ISO

F

 

S

O

1,340

 

Ethohexadiol

N(A)

RP (insect)

 

L

O

2,400

 

Etridiazole

ISO

F

 

L

O

2,000

 

Fenoprop

ISO

H

 

S

O

650

 

Fenson

ISO

AC

 

S

O

1,550

 

Fenothiocarb

ISO

L

C

S

O

1,150

 

Fenpropidin

ISO

F

 

S

O

1,440

 

Fenthiaprop

N(B)

H

 

S

O

915

 

Ferimzone

ISO

F

 

S

O

725

 

Flamprop

ISO

H

 

S

O

1,210

 

Fluchloralin

ISO

H

 

S

O

1,550

 

Fluoroglycofen

N(B)

H

 

S

O

1,500

 

Flurprimidol

ISO

PGR

 

S

O

709

 

Flusilazole

N(B)

F

 

S

O

1,110

 

Flutriafol

ISO

F,FST

T

S

O

1,140

 

Fomesafen

ISO

H

OC

S

O

1,250

 

Fuberidazole

ISO

F

 

S

O

1,100

 

Furalaxyl

ISO

F

 

S

O

940

 

Glufosinate

ISO

H

 

S

O

1,625

 

Heptopargil

ISO

PGR

 

L

O

2,100

 

Hexazinone

ISO

H

 

S

O

1,690

 

Hydramethylnon

N(A,B)

I

 

S

O

1,200

 

IBP

 

 

 

 

 

 

See iprobenphos

Iprobenphos

N(B)

F

 

S

O

600

 

Isoprothiolane

ISO

F

 

S

O

1,190

 

Isoproturon

ISO

H

 

S

O

1,800

 

Isouron

ISO

H

 

S

O

630

 

Isoxapyrifop

ISO

H

 

S

O

500

 

Kelthane

N(J)

 

 

 

 

 

See dicofol

Malathion

ISO

I

OP

L

O

c2,100

LD50 value can vary according to impurities.   This value has been adopted for classification   purposes and is that of a technical product   conforming to WHO specifications; DS 29

Maldison

N(Aus,NZ)

 

 

 

 

 

See malathion

MCPA

ISO

H

 

S

O

700

 

MCPA-thioethyl

ISO

H

 

S

O

790

 

MCPB

ISO

H

 

S

O

680

 

Mecoprop

ISO

H

 

S

O

930

 

Mecoprop-P

ISO

H

 

S

O

1,050

 

Mefluidide

ISO

H

 

S

O

1,920

 

Menazon

ISO

AP

OP

S

O

1,950

 

Mepiquat

ISO

PGR

 

S

O

1,490

 

Metalaxyl

ISO

F

 

S

O

670

 

Metaxon

N(U)

 

 

 

 

 

See MCPA

Metconazole

ISO

F

 

S

O

660

 

Methazole

N(A,B)

H

 

S

O

4,543

Slightly irritant to eyes

2-Methoxyethlymercury silicate

C

FST

OM

S

O

1,140

 

Methylarsonic acid

ISO

H

 

S

O

1,800

 

Metolachlor

ISO

H

 

L

O

2,780

 

MSMA

 

 

 

 

 

 

See methylarsonic acid

Myclobutanil

N(B)

F

 

S

O

1,600

 

2-Napthyloxy acetic acid

ISO

PGR

 

S

O

600

 

Nitrapyrin

ISO

B-S

 

S

O

1,072

 

Nuarimol

ISO

F

 

S

O

1,250

 

Octhilinone

ISO

F

 

S

O

1,470

 

N-octyl bicycloheptene  dicarboximide

C

SY

 

L

O

2,800

 

Oxadixyl

N(B)

F

 

S

O

1,860

 

Paclobutrazol

ISO

PGR

 

S

O

1,300

 

Pallethrine

N(F)

 

 

 

 

 

See allethrin

Para-dichlorobenzene

 

 

 

 

 

 

See dichlorobenzene

Pendimethalin

ISO

H

 

S

O

1,050

 

Perfluidone

ISO

H

 

S

O

920

 

Pimaricin

N(B)

F

 

S

O

2,730

Antibiotic, identical with tennecetin and   natamycin

Piproctanyl

ISO

PGR

 

S

O

820

 

Pirimiphos-methyl

ISO

I

OP

L

O

2,018

DS 49

Prochloraz

ISO

F

 

S

O

1,600

 

Propachlor

ISO

H

 

S

O

1,500

DS 78

Propanil

ISO

H

 

S

O

c1,400

 

Propargite

ISO

AC

 

L

O

2,200

 

Pyrazoxyfen

ISO

H

 

S

O

1,644

 

Pyridaben

ISO

AC

 

S

O

820

 

Pyridaphenthion

N(J)

I

OP

S

O

769

 

Pyridate

ISO

H

 

S

O

c2,000

 

Pyrifenox

ISO

F

 

L

O

2,900

 

Quinoclamine

ISO

H

 

S

O

1,360

 

Quizalofop

N(B)

H

 

S

O

1,670

 

Resmethrin

ISO

I

PY

S

O

2,000

See cismethrin; EHC 92, DS 83, HSG 25

Ryania

C

I

 

S

O

c750

LD50 varies: vegetable product

Sesamex

N(A)

SY

 

L

O

2,000

 

Sethoxydim

ISO

H

 

L

O

3,200

 

Silvex

N(A)

 

 

 

 

 

See fenoprop

Simetryn

ISO

H

T

S

O

1,830

 

Sodium chlorate

ISO

H

 

S

O

1,200

 

Sulfluramid

ISO

I

 

S

O

543

 

Sulfoxide

N(A)

SY

 

L

O

2,000

 

2,3,6-TBA

ISO

H

 

S

O

1,500

 

Tebuthiuron

ISO

H

 

S

O

644

 

Thiram

ISO

F

 

S

O

560

DS 71

TMTD

N(U)

 

 

 

 

 

See thiram

2,4,5-TP

N(F,J,U)

 

 

 

 

 

See fenoprop

Tralkoxydim

ISO

H

 

S

O

934

 

Triadimefon

ISO

F

 

S

O

602

 

Triadimenol

ISO

FST

 

S

O

900

 

Tri-allate

ISO

H

TC

L

O

2,165

HSG 89

Trichlorfon

ISO

H

OP

S

O

560

DS 27; EHC 132; HSG 66

Triclopyr

ISO

H

 

S

O

710

 

Tridiphane

N(B)

H

 

S

O

1,740

 

Trifenmorph

ISO

M

 

S

O

1,400

DS 64

Triflumizole

N(B)

F

 

S

O

695

 

Undecan-2-one

C

RP  (dogs,cats)

 

oil

O

2,500

 

Uniconazole

ISO

PGR

 

S

O

1,790

 

XMC

N(J)

I

C

S

O

542

 

Ziram

ISO

F

 

S

O

1,400

Irritant to skin; DS 73

Source: WHO 1996.

Table 62.5 List of technical products unlikely to present acute hazard in normal use

Name

Status

Main use

Chemical  type

Physical  state

Route

LD50  (mg/kg)

Remarks

Aclonifen

N(B)

H

 

S

O

+5,000

 

Acrinathrin

ISO

MT

 

S

O

+5,000

 

Alloxydim

ISO

H

 

S

O

2,260

 

Aminotriazole

N(F)

 

 

 

 

 

See amitrole

Amitrole

ISO

H

T

S

O

5,000

EHC 158, DS 79; HSG 85

Ammonium sulfamate

ISO

H

 

S

O

3,900

 

Ancymidol

ISO

PGR

 

S

O

4,500

 

Anilazine

ISO

F

T

S

O

2,710

Irritant to eyes and skin

Anthraquinone

ISO

RP (birds)

 

S

O

+5,000

 

Asulam

ISO

H

TC

S

O

+4,000

 

Atrazine

ISO

H

T

S

O

c2,000

DS 82; HSG 47

Aziprotryne

ISO

H

T

S

O

3,600

 

Benalaxyl

ISO

F

 

S

O

c4,200

 

Benazolin

ISO

H

 

S

O

3,200

Irritant to skin and eyes

Benefin

N(A)

 

 

 

 

 

See benfluralin

Benfluralin

ISO

H

 

S

O

+10,000

 

Benfuresate

ISO

H

 

S

O

2,031

 

Benomyl

ISO

F

TC

S

O

+10,000

EHC 148, DS 87; HSG 81

Benoxacor

ISO

H

 

S

O

+5,000

 

Bensulfuron

N(B)

H

 

S

O

+5,000

 

Benthrodine

N(J)

 

 

 

 

 

See benfluralin

Benzamizole

 

 

 

 

 

 

See isoxaben

Benzoximate

ISO

AC

 

S

O

+10,000

 

Bifenox

ISO

H

 

S

O

+6,400

 

Bioresmethrin

ISO

I

PY

L

O

+7,000

DS 34

Biphenyl

ISO

F

 

S

O

3,280

 

Bispyribac

ISO

H

 

S

O

2,635

 

Bitertanol

ISO

F

 

S

O

+5,000

 

Borax

ISO

F

 

S

O

4,500

 

Bromacil

ISO

H

 

S

O

5,200

 

Bromobutide

ISO

H

 

S

O

+5,000

 

Bromocyclen

ISO

I,AC

 

S

O

+10,000

 

Bromopropylate

ISO

AC

 

S

O

+5,000

 

Bupirimate

ISO

F

 

S

O

c4,000

 

Buprofezin

ISO

I

 

S

O

2,200

 

Butachlor

ISO

H

 

L

O

3,300

 

Buthiobate

ISO

F

 

L

O

3,200

 

Butopyronoxyl

N(A)

RP  (insects)

 

L

O

7,840

 

Butralin

ISO

H

 

S

O

+10,000

 

Buturon

ISO

H

 

S

O

3,000

 

Butylate

ISO

F

TC

L

O

+4,000

 

Captan

ISO

F

 

S

O

9,000

Irritant to skin; DS 9; HSG 50

Carbendazim

ISO

F

 

S

O

+10,000

DS 89; EHC 149; HSG 82

Carbetamide

ISO

H

 

S

O

+10,000

 

Carboxin

ISO

FST

 

S

O

3,820

 

Chinomethionat

ISO

AC,F

 

S

O

2,500

 

Chlomethoxyfen

N(B)

H

 

S

O

+10,000

 

Chloramben

ISO

H

 

S

O

5,620

 

Chlorbromuron

ISO

H

 

S

O

+5,000

 

Chlorbufam

ISO

H

 

S

O

2,500

 

Chlorfenidim

N(U)

 

 

 

 

 

See monuron

Chlorfluazuron

ISO

IGR

 

S

O

8,500

 

Chlorflurecol

N(B)

 

 

 

 

 

See chlorflurenol

Chlorflurenol

ISO

PGR

OC

S

O

+10,000

 

Chloridazon

ISO

H

 

S

O

2,420

 

Chlorimuron

N(B)

H

 

S

O

4,102

 

Chlornitrofen

ISO

H

 

S

O

+10,000

 

Chloromethiuron

ISO

Ix

 

S

O

2,500

 

Chloroneb

ISO

H

OC

S

O

+10,000

 

Chloropropylate

ISO

AC

OC

S

O

+5,000

 

Chlorothalonil

ISO

F

 

S

O

+10,000

 

Chlorotoluron

ISO

H

 

S

O

+10,000

 

Chloroxifenidim

N(U)

 

 

 

 

 

See chloroxuron

Chloroxuron

ISO

H

 

S

O

+3,000

 

Chlorphoxim

ISO

I

OP

S

O

+2,500

DS 32

Chlorpropham

ISO

H

 

S

O

+5,000

 

Chlorpyrifos methyl

ISO

I

OP

L

O

+3,000

DS 33

Chlorsulfuron

ISO

H

 

S

O

5,545

 

Chlorthal-dimethyl

ISO

H

 

S

O

+3,000

 

Chlozolinate

N(B)

F

 

S

O

+4,000

 

Cinmethylin

ISO

H

 

L

O

3,960

 

Cinosulfuron

ISO

H

 

S

O

+5,000

 

Clofentezine

N(B)

AC

 

S

O

+5,200

 

Clomeprop

ISO

H

 

S

O

+5,000

 

Clonitralide

N(A)

 

 

 

 

 

See niclosamide

Clopyralid

N(B)

H

 

S

O

4,300

Severe irritant to eyes

Cloxyfonac

ISO

PGR

 

S

O

+5,000

 

CNA

N(J)

 

 

 

 

 

See dicloran

COMU

N(J)

 

 

 

 

 

See cycluron

Credazine

N(J)

H

 

S

O

3,090

 

Cryolite

C

I

 

S

O

+10,000

 

Cycloprothrin

ISO

I

PY

L

O

+5,000

 

Cycloxydim

N(B)

H

 

S

O

3,900

 

Cycluron

ISO

H

 

S

O

2,600

 

Cyometrinil

N(B)

H

 

S

O

2,277

 

Cyromazine

ISO

L

 

S

O

3,300

 

Caimuron

ISO

H

 

S

O

+5,000

 

Dalapon

N(A,B,F)

H

 

S

O

9,330

 

Daminozide

ISO

H

 

S

O

8,400

 

Desmedipham

ISO

H

 

S

O

+9,600

 

Diafenthiuron

ISO

AC

 

S

O

2,068

 

Dichlobenil

ISO

H

 

S

O

3,160

 

Dichlorfenidim

N(U)

 

 

 

 

 

See diuron

Dichlofluanid

ISO

F

 

S

O

+5,000

 

Dichloropicolinic acid

 

 

 

 

 

 

See clopyralid

Diclobutrazol

ISO

F

T

S

O

+4,000

 

Diclomezine

ISO

F

 

S

O

+10,000

 

Dicloran

N(B)

F

 

S

O

4,000

 

Diethatyl

ISO

H

 

S

O

2,300

 

Diethofencarb

ISO

F

 

S

O

+5,000

 

Difenoxuron

ISO

H

 

S

O

+7,750

 

Diflubenzuron

ISO

L

 

S

O

+4,640

DS 77

Diflufenican

N(B)

H

 

S

O

+2,000

 

Dikegulac

ISO

PGR

 

S

O

+10,000

 

Dimefuron

ISO

H

 

S

O

+2,000

 

Dimethirimol

ISO

F

 

S

O

2,350

 

Dimethomorph

ISO

F

 

S

O

+5,000

 

Dimethyl phthalate

C

RP  (insect)

 

L

O

8,200

 

Dinitramine

ISO

H

 

S

O

3,000

 

Diphenyl

 

 

 

 

 

 

See biphenyl

Dipropetryn

ISO

H

T

S

O

4,050

 

Dipropyl isocinchomerate

C

RP (fly)

 

L

O

5,230

 

Disodium octaborate

 

 

 

 

 

 

See borax

Ditalmifos

ISO

F

OP

S

O

5,660

Irritant to skin; allergenic

Dithiopyr

ISO

H

 

 

O

+5,000

 

Diuron

ISO

H

 

S

O

3,400

 

Dodemorph

ISO

H

 

L

O

4,500

 

Eglinazine

ISO

H

 

S

O

+10,000

 

Ethalfluralin

ISO

H

 

S

O

+10,000

 

Ethephon

N(A)

PGR

 

S

O

+4,000

 

Ethidimuron

ISO

H

 

S

O

+5,000

 

Ethirimol

ISO

FST

 

S

O

6,340

 

Ethofumesate

ISO

H

 

S

O

+6,400

 

Etofenprox

N(B)

I

 

S

O

+10,000

 

Fenarimol

ISO

F

 

S

O

2,500

 

Fenbutatin oxide

ISO

MT

OT

S

O

2,630

EHC 15

Fenchlorazole

ISO

H

 

S

O

+5,000

 

Fenclorim

ISO

H

 

S

O

+5,000

 

Fenfuram

ISO

FST

 

S

O

+10,000

 

Fenidim

N(U)

 

 

 

 

 

See fenuron

Fenitropan

ISO

F

 

S

O

3,230

 

Fenoxaprop-ethyl

N(B)

H

 

S

O

2,350

 

Fenoxycarb

ISO

I

C

S

O

+10,000

 

Fenpiclonil

ISO

FST

 

S

O

+5,000

 

Fenpropimorph

ISO

F

 

oil

O

3,515

 

Fenuron

ISO

H

 

S

O

6,400

 

Fenuron-TCA

(ISO)

H

 

S

O

4,000

 

Ferbam

ISO

F

TC

S

O

+10,000

 

Flamprop-M

ISO

H

 

S

O

+3,000

 

Fluazifop

ISO

H

P

L

O

3,330

 

Flubenzimine

ISO

AC

 

S

O

3,000

 

Flucycloxuron

ISO

AC

 

S

O

+5,000

 

Flufenoxuron

ISO

I

 

S

O

+3,000

 

Flumetralin

N(B)

PGR

 

S

O

+5,000

 

Flumetsulam

ISO

H

 

S

O

+5,000

 

Fluometuron

ISO

H

 

S

O

+8,000

 

Fluorodifen

ISO

H

 

S

O

9,000

 

Fluoromide

N(J)

F

 

S

O

+10,000

 

Flupropanate

ISO

H

 

S

O

+10,000

 

Flurecol butyl

 

 

 

 

 

 

See flurenol

Flurenol

ISO

PGR

 

S

O

+5,000

 

Fluridone

ISO

H

 

S

O

+10,000

 

Flurochloridone

ISO

H

 

S

O

4,000

 

Fluthiacet

ISO

H

 

S

O

+5,000

 

Fluroxypyr

N(B)

H

 

S

O

+5,000

 

Fluthiacet

ISO

H

 

S

O

+5,000

 

Flutolanil

ISO

F

 

S

O

+10,000

 

Tau-fluvalinate

ISO

I

PY

oil

O

+3,000

Skin and eye irritant

Folpet

ISO

F

 

S

O

+10,000

HSG 72

Fosamine

ISO

H

 

S

O

2,400

 

Fosetyl

N(B)

F

 

S

O

5,800

 

Furmecyclox

N(B)

FST

 

S

O

3,780

 

Gibberellic acid

N(B)

PGR

 

S

O

+10,000

 

Glyphosate

ISO

H

 

S

O

4,230

EHC 159, DS 91

Glyphosine

ISO

H

 

S

O

3,920

 

Hexaconazole

N(B)

F

 

S

O

2,180

 

Hexaflumuron

ISO

I

 

S

O

+5,000

 

Hexythiazox

N(B)

AC

 

S

O

+5,000

 

Hydroprene

N(A)

IGR

 

L

O

+10,000

 

2-Hydroxyethyl octyl sulphide

C

RP  (insect)

 

L

O

8,530

 

Hydroxyisoxazole

N(J)

 

 

 

 

 

See hymexazol

Hymexazol

N(B)

FST

 

S

O

3,900

 

Imazamethabenz-methyl

(ISO)

H

 

S

O

+5,000

 

Imazapyr

ISO

H

 

S

O

+5,000

Irritant to eyes

Imazaquin

ISO

H

 

S

O

+5,000

 

Imazethapyr

N(B)

H

 

S

O

+5,000

 

Imibenconazole

ISO

F

 

S

O

+5,000

 

Inabenfide

ISO

PGR

 

S

O

+10,000

 

Iodofenphos

N(A,B)

 

 

 

 

 

See jodfenphos

Iprodione

ISO

F

 

S

O

3,500

 

Isopropalin

ISO

H

 

L

O

+5,000

 

Isoxaben

N(B)

H

 

S

O

+10,000

 

Jodfenphos

ISO

I

OP

S

O

2,100

DS 43

Karbutilate

ISO

H

 

S

O

3,000

 

Kasugamycin

N(J)

F

 

S

O

+10,000

 

Kinoprene

ISO

IGR

 

S

O

4,900

 

Lenacil

ISO

H

 

S

O

+10,000

 

Linuron

ISO

H

 

S

O

4,000

 

Maleic hydrazide

ISO

PGR

 

S

O

6,950

 

Mancozeb

ISO

F

TC

S

O

+8,000

Irritant to skin on multiple exposure; DS 94

Maneb

ISO

F

TC

S

O

6,750

Irritant to skin on multiple exposure; DS 94

Mefenacet

ISO

H

 

S

O

+5,000

 

Mepanipyrim

ISO

F

 

S

O

+5,000

 

Mepronil

N(J)

F

 

S

O

+10,000

 

Metamitron

ISO

H

 

S

O

3,343

 

Metazachlor

ISO

H

 

S

O

2,150

 

Methabenzthiazuron

ISO

H

 

S

O

+2,500

 

Methoprene

ISO

IGR

 

L

O

+10,000

DS 47

Methoprotryne

ISO

H

 

S

O

+5,000

 

Methoxychlor

ISO

I

OC

S

O

6,000

DS 28

Methoxyphenone

N(J)

H

 

S

O

+4,000

 

Methyldymron

N(J)

H

 

S

O

3,948

 

Metiram

N(J)

F

 

S

O

+10,000

 

Metobromuron

ISO

H

 

S

O

2,500

 

Metosulam

ISO

H

 

S

O

+5,000

 

Metoxuron

ISO

H

 

S

O

+3,200

 

Metribuzin

ISO

H

T

S

O

2,200

 

Metsulfovax

ISO

F

 

S

O

3,929

 

Metsulfuron

N(A,B)

H

 

S

O

+5,000

 

Monalide

ISO

H

 

S

O

+4,000

 

Monolinuron

ISO

H

 

S

O

2,250

 

Monuron

ISO

H

 

S

O

3,600

 

Monuron-TCA

N(A)

H

 

S

O

3,700

 

Naphthalene

C

F

 

S

O

2,200

 

Naphthalic anhydride

C

PGR

 

S

O

+10,000

 

2-(1-naphthyl) acetamide

ISO

PGR

 

S

O

6,400

 

1-naphthylacetic acid

ISO

PGR

 

S

O

c3,000

 

Napropamide

ISO

H

 

S

O

5,000

 

Naptalam

ISO

PGR

 

S

O

8,200

 

Neburon

ISO

H

 

S

O

+10,000

 

Niclosamide

ISO

M

 

S

O

5,000

DS 63

Nicosulfuron

ISO

H

 

S

O

+5,000

Irritant to eyes

Nitralin

ISO

H

 

S

O

+2,000

 

Nitrothal-isopropyl

ISO

F

 

S

O

6,400

 

Norflurazon

ISO

H

 

S

O

+8,000

 

(octylthio)ethanol

C

 

 

 

 

 

See 2-hydroxyethyl octyl sulphide

Ofurace

ISO

F

 

S

O

2,600

 

Oryzalin

ISO

H

 

S

O

+10,000

 

Oxabetrinil

ISO

H

 

S

O

+5,000

 

Oxadiazon

ISO

H

 

S

O

+8,000

 

Oxine copper

ISO

F

 

S

O

10,000

 

Oxycarboxin

ISO

F

 

S

O

2,000

 

Oxyfluorfen

ISO

H

 

S

O

+5,000

 

Penconazole

N(B)

F

 

S

O

2,120

 

Pencycuron

ISO

F

 

S

O

+5,000

 

Pentanochlor

ISO

H

 

S

O

+10,000

 

Phenisobromolate

N(J)

 

 

 

 

 

See bromopropylate

Phenisopham

ISO

H

 

S

O

+4,000

 

Phenmedipham

ISO

H

 

S

O

+8,000

 

Phenothrin

ISO

I

PY

L

O

+5,000

DS 85; EHC 96; HSG 32

2-Phenylphenol

ISO

F

 

S

O

2,480

 

Phosdiphen

N(J)

F

 

L

O

6,200

 

Phthalide

N(J)

F

 

S

O

+10,000

 

Picloram

ISO

H

 

S

O

8,200

 

Piperonyl butoxide

N(A)

SY

 

oil

O

+7,500

 

Pretilachlor

ISO

H

 

L

O

6,100

 

Primisulfuron

ISO

H

 

S

O

+5,050

 

Probenazole

N(J)

F

 

S

O

2,030

 

Procymidone

ISO

F

 

S

O

6,800

 

Prodiamine

ISO

H

 

S

O

+5,000

 

Profluralin

ISO

H

 

S

O

c10,000

 

Proglinazine

ISO

H

 

S

O

+8,000

 

Prometon

ISO

H

T

S

O

2,980

 

Prometryn

ISO

H

T

S

O

3,150

 

Pronamide

N(A)

 

 

 

 

 

See propyzamide

Propamocarb

ISO

F

 

S

O

8,600

 

Propaquizafop

ISO

H

 

S

O

+5,000

 

Propazine

ISO

H

T

S

O

+5,000

 

Propham

ISO

H

 

S

O

5,000

 

Propineb

ISO

H

TC

S

O

8,500

 

Propyzamide

ISO

H

 

S

O

5,620

 

Pyracarbolid

ISO

F

 

S

O

+10,000

 

Pyrazolynate

ISO

H

 

S

O

9,550

 

Pyrazon

N(A)

 

 

 

 

 

See chloridazon

Pyrazosulfuron

ISO

H

 

S

O

+5,000

 

Pyrimethanil

ISO

F

 

S

O

4,150

 

Pyriminobac

ISO

H

 

S

O

+5,000

 

Pyriproxyfen

N(B)

I

 

S

O

+5,000

 

Quinclorac

ISO

H

 

S

O

2,680

 

Quinmerac

ISO

H

 

S

O

+5,000

 

Quinomethinoate

N(B)

 

 

 

 

 

See chinomethionat

Quinonamid

ISO

F

 

S

O

+10,000

 

Quintozene

ISO

F

 

S

O

+10,000

EHC 41

Rimsulfuron

C

H

 

S

O

+5,000

 

Secbumeton

ISO

H

T

S

O

2,680

 

Siduron

ISO

H

 

S

O

+7,500

 

Simazine

ISO

H

T

S

O

+5,000

 

Sodium metaborate

C

 

 

 

 

 

See borax

Sodium trichloracetate

 

 

 

 

 

 

The data shown refer to sodium trichloroacetic acid.   In many countries, the term TCA refers   to the free acid (now accepted by ISO): this   is a solid with an oral LD50 of 400 mg/kg   and if used as a pesticide is placed in Class II.   It is highly corrosive to skin

Solan

N(A)

 

 

 

 

 

See pentanochlor

Stirofos

N(A)

 

 

 

 

 

See tetrachlorvinphos

Sulfometuron

N(B)

H

 

S

O

+5,000

 

Sulfur

N(A,J)

 

 

 

 

 

See sulphur

Sulphur

ISO

F,I

 

S

O

+3,000

Irritant to skin and mucous membranes. Sulphur dust   can spontaneously ignite unless diluted about 50% with   inert material

TCA

ISO

H

 

S

O

3,200

Irritant to skin and eyes; see sodium trichloracetate

Tebuconazole

ISO

F

 

S

O

4,000

 

Tebutam

ISO

H

 

oil

O

6,210

 

Tecnazene

ISO

F

 

S

O

+10,000

EHC 42; HSG 12

Tedion

N(U)

 

 

 

 

 

See tetradifon

Teflubenzuron

N(B)

I

 

S

O

+5,000

 

Temephos

ISO

I

OP

L

O

8,600

DS 8

Terbacil

ISO

H

 

S

O

+5,000

 

Terbuthylazine

ISO

H

T

S

O

2,160

 

Terbutryn

ISO

H

T

S

O

2,400

 

Tetrachlorvinphos

ISO

I

OP

S

O

4,000

 

Tetradifon

ISO

AC

 

S

O

+10,000

EHC 67; HSG 11

Tetramethrin

ISO

O

PY

S

O

+5,000

EHC 98; HSG 31

Tetrasul

ISO

AC

 

S

O

6,810

 

Thiabendazole

ISO

F

 

S

O

3,330

 

Thidiazuron

ISO

PGR

 

S

O

+4,000

 

Thifensulfuron

N(B)

H

 

S

O

+5,000

 

Thiophanate

ISO

F

 

S

O

+10,000

 

Thiophanate-methyl

ISO

F

 

S

O

+6,000

 

Tiocarbazil

ISO

H

TC

L

O

10,000

 

Tolclofos-methyl

ISO

F-S

 

S

O

c5,000

 

Tolyfluanid

ISO

F

 

S

O

+5,000

 

Transfluthrin

ISO

I

PY

S

O

+5,000

 

Triasulfuron

ISO

H

 

S

O

+5,000

 

Tribenuron

N(B)

H

 

S

O

+5,000

 

Trichlamide

ISO

F

 

S

O

+5,000

 

Trietazine

ISO

H

T

S

O

2,830

 

Trifluralin

ISO

H

 

S

O

+10,000

 

Triflumuron

ISO

PGR

 

S

O

+5,000

 

Triforine

ISO

F

 

S

O

+6,000

 

Triticonazole

N(B)

F

triazole

S

O

+2,000

 

Validamycin

N(J)

F

 

S

O

+10,000

 

Vinclozolin

ISO

F

 

S

O

10,000

 

Zineb

ISO

F

 

S

O

+5,000

DS 94

Source: WHO 1996.

Table 62.6 Technical products not included in the WHO Classification and believed to be obsolete or discontinued for use as pesticides

Allyxycarb

Dinex

Methacarbate

Amidithion

Dinocton

Methiuron

Aramite

Endothion

2-Methoxymethyl mercury chloride (DS 66)

Athidithion

Erbon

Methylmercury dicyandiamide

Atraton

Ethiolate

Mexacarbate

Azothoate

Ethoate-methyl

Mipafox

Barium carbonate

Ethyleneglycol

Mirex (EHC 44; HSG 39)

Benodanil

Bis(trichloracetate)

Morfamquat

Benquinox

EXD

Myclozolin

Butacarb

Fenazaflor

Nitrilacarb

Butam

Fluotrimazole

Noruron

Butonate

Fosthietan

Oxapyrazon

Calcium cyanamide

Fluenetil

Oxydisulfoton

Carbamorph

Glyodin

Parafluron

Carbanolate

Griseofulvin

Phenkapton

Chloethocarb

Halacrinate

Phenobenzuron

Chloraniformethan

Haloxydine

Phenylmercury dimethyldithiocarbamate

Chloranil

Hexachloroacetone

Phosacetim

Chloranocryl

Hexaflurate

Potassium cyanate

Chlorbenside

Hydroxyquinoline sulfate

Propyl isome

Chlorbicyclen

Ipazine

Prothiocarb

Chlordecone (EHC 43; HSG 41)

IPSP

Proxan

Chlorfenprop-methyl

Isobenzan

Pydanon

Chlorfensulphide

Isobornyl thiocyanoacetate

Pyridinitril

Chlorfentezine

Isocarbamid

Quinacetol-sulfate

Chloromebuform

Isocil

Sabadilla

Chlorquinox

Isodrin

Salicylanilide

Crimidine

Isomethiozin

Schradan

Cyanthoate

Isonoruonlisoprothiolane

Swep

Cypendazole

Kelevan (EHC 66; HSG 2)

TDE

Cypromid

Lythidathion

Terbucarb

Delachlor

Malonoben

Thioquinox

Diamidafos

MCC

Triapenthenol

Dibutyl phthalate

Mebenil

Triarimol

Dibutyl succinate

Mecarbinzid

Tricamba

Dichlozoline

Mecarphon

Trichloronat

Dimexano

Medinoterb acetate

Trimethacarb

Source: WHO 1996.

Table 62.7 List of gaseous or volatile fumigants not classified under the WHO Recommended Classification of Pesticides by Hazard

Acrylonitrile (EHC 28; HSG 1)

Ethylene dichloride (EHC 176)

Aluminium phosphide (EHC 73; HSG 28)

Ethylene oxide (EHC 55; HSG 16)

Carbon disulfide (EHC 10)

Formaldehyde (EHC 89; HSG 57)

Chloropicrin

Hydrogen cyanide

1,2-Dichloropropane (EHC 146; HSG 76)

Magnesium phosphide (EHC 73; HSG 28)

1,3-Dichloropropene (EHC 146; HSG 76)

Methyl bromide (DS 5; EHC 166; HSG 86)

Epoxyethane (ethylene oxide) (EHC 55; HSG 16)

Phosphine (DS 46; EHC 73; HSG 28)

Ethylene dibromide (EHC 177)

Sulfuryl fluoride

Note: The WHO Classification does not set out any criteria for air concentrations on which classification  could be based. Most of these compounds are of high hazard and recommended exposure limits for  occupational exposure have been adopted by national authorities in many countries.

Source: WHO 1996.

The entries and abbrevations used in the tables’ various columns are explained here under the corresponding heading.

Name

The first column in the tables list the approved name of active ingredients. Trade names are not listed since there are many of these.

Status

The following abbreviations are used:

·     ISO: Indicates the common name approved by the International Organization for Standardization (ISO). Such names are, when available, preferred by the WHO to all other common names. However, some of these names may not be acceptable for national use in some countries. If the letters ISO appear within parentheses (e.g., with fentin acetate), this indicates that ISO has standardized (or is in the process of standardizing) the name of the base, but not the name of the derivative listed in the “Name” column. (Fentin is an ISO name, but fentin acetate is not.)

·     N( ): Indicates approval by a national ministry or other body, which is shown in parentheses as follows: A: United States Environmental Protection Agency (EPA), American National Standards Institute (ANSI), the Weed Science Society of America or the Entomological Society of America; B: British Standards Institution or the British Pharmacopoeia Commission; F: Association française de normalisation; J: Japanese Ministry of Agriculture and Forestry; U: Gosudarstvennyi Komitet Standartov, former USSR.

·     C: Chemical, trivial or other common name.

Main use

In most cases only a single use is given. This is only for identification purposes and does not exclude other uses. The following abbreviations are used:

·     AC: acaricide

·     AP: aphicide

·     B: bacteriostat (soil)

·     FM: fumigant

·     F: fungicide, other than for seed treatment

·     FST: fungicide, for seed treatment

·     H: herbicide

·     I: insecticide

·     IGR: insect growth regulator

·     Ix: ixodicide (for tick control)

·     L: larvicide

·     M: molluscicide

·     N: nematocide

·     O: other use for plant pathogens

·     PGR: plant growth regulator

·     R: rodenticide

·     RP( ): repellent (species)

·     -S: applied to soil; not used with herbicides or PGRs

·     SY: synergist.

Chemical type

A limited number of chemical types are shown in this column. Most have some significance in the sense that they may have a common antidote or may be confused in the nomenclature with other chemical types. For example, thiocarbamates are not cholinesterase inhibitors and do not have the same effects as carbamates. The following abbreviations are used:

·     C: carbamate

·     CNP: chloronitrophenol derivative

·     OC: organochlorine compound

·     OM: organomercury compound

·     OP: organophosphorus compound

·     OT: organotin compound

·     P: pyridyl derivative

·     PA: phenoxyacetic acid derivative

·     PY: pyrethroid

·     T: triazine derivative

·     TC: thiocarbamate.

These chemical classification are included only for convenience and do not represent a recommendation on the part of the WHO as to the way in which pesticides should be classified. It should, furthermore, be understood that some pesticides may fall into more than one type.

Chemical type is not shown where it is apparent from the name.

Physical state

This refers only to the technical compound. The following are used:

·     L: liquid, including solids with a melting point below 50°C

·     oil: oily liquid; refers to physical state only

·     S: solid, includes waxes.

It may happen in a few cases that where the technical product is a solid, highly concentrated liquid formulations may need to be classified in a more hazardous class. In most cases, oils have been classified as liquids unless very viscous at ordinary temperatures.

Route

Oral route values are used unless the dermal route values place the compound in a hazardous class or the dermal values are significantly lower than the oral values, although in the same class. The following abbreviations are used:

·     D: dermal

·     O: oral.

LD50 (mg/kg)

The LD50 value is a statistical estimate of the number of mg of toxicant per kg of body weight required to kill 50% of a large population of test animals; the rat is used unless otherwise states. A single value is given: “c” preceding the value indicates that it is a value within a wider than usual range, adopted for classification purposes; “+” preceding the value indicates that the kill at the stated dose was less than 50% of the test animals.

The toxicity data for pyrethroids are highly variable according to isomer ratios, the vehicle for oral administration and the husbandry of the test animals. The variability is reflected in the prefix “c”. The single LD50 value now chosen for classification purposes is based on administration in corn oil and is much lower than that in aqueous solutions. This has resulted in considerable changes in the classification of some products and also underlines the need for classification by formulation if labelling is to reflect true hazard.

The figures in this column are not median values; rather, a safety margin is incorporated by choosing the lower confidence limit in most cases. Where a sex difference occurs in LD50 values, the value for the more sensitive sex is used. A number of classification adjustments have been made in respect of some pesticides and these are explained. A borderline case has been classified in the more or less hazardous class after consideration of its toxicology and use experience.

In table 62.5, a number of pesticides are listed as unlikely to present any acute hazard in normal use. The WHO Classification is open-ended but it is clear that there must be a point at which the acute hazard posed by the use of these compounds is so low as to be negligible provided that the necessary precautions are taken. For the purposes of this table, it has been assumed that this point is an oral LD50 of 2,000 mg/kg for solids and 3,000 mg/kg for liquids. However, it should not be overlooked that in formulations of these technical products, solvents or vehicles may present a greater hazard than the actual pesticide and therefore classification of a formulation in one of the higher hazard classes may be necessary.

Biological pesticides are not included in the WHO Classification because the methods of the safety testing of live biological agents are not appropriate to classification procedures applied to chemical compounds.

Remarks

Where the classification of a technical product has been adjusted, the basis for this is indicated in this column. Major irritant properties are noted; these do not affect classification. Where the name of a technical product is cross-referenced, the referenced product will be found in the same table. Abbreviations are used to indicate that a WHO/FAO Data Sheet (DS) or an issue of International Programme on Chemical Safety (IPCS) Environmental Health Criteria (EHC) Series or Health and Safety Guide contains further information on the product; the relevant issue numbers follow the abbreviations.

REFERENCES

World Health Organization (WHO). 1996. The WHO Recommended Classification of Pesticides by Hazard and Guidelines to Classification 1996-1997. International Programme on Chemical Safety (IPCS), WHO/PCS/96.3. Geneva: WHO.

OTHER RELEVANT READINGS

Armstrong, LD, and AR Stiles. 1973. Pesticides: Nomenclature, specifications, analysis, uses and residues in food. Bull Wld Hlth Org 49:169-204.

International Programme on Chemical Safety (IPCS). 1994. Summary of Toxicological Evaluations Performed by the Joint FA0/WHO Meeting on Pesticide Residues (JMPR) 1990. WHO/PCS/95.4. Geneva: IPCS.

Tomlin, C. (ed.). 1994. The Pesticide Manual: A World Compendium, 10th ed. Thornton Weath, UK: British Crop Protection Council.

Wiswesser, WJ. 1976. Pesticide Index. College Park, MD: College Science Publishers and Entomological Society of America.