333-41-5

Diazinon is available as a colorless or dark brown liquid. It is sparingly soluble in water but very soluble in petroleum ether, alcohol, and benzene. Diazinon is used for the control of a variety of agricultural and household pests. These include pests in soil, on ornamental plants, fruit, vegetable, crops pests, and household pests like fl ies, fl eas, and cockroaches. Diazinon undergoes decomposition on heating above 120°C and produces toxic fumes, such as nitrogen oxides, phosphorous oxides, and sulfur oxides. It reacts with strong acids and alkalis with the possible formation of highly toxic tetra ethyl thiopyrophosphates. Diazinon is classifi ed as an RUP. Depending on the type of formulation, diazinon is classifi ed as toxicity class II, meaning moderately toxic, or toxicity class III, meaning slightly toxic.

Liquid; light to dark brown. Sinks in water. Commercial solutions can contain ethanol/xylene/acetone with a flash point in the range 82-105 °F

The neat compound is susceptible to oxidation and should be protected from prolonged exposure to air . Insoluble in water.

Humans are exposed to diazinon during manufacture and professional applications. Diazinon causes poisoning with symptoms such as headache, dizziness, nausea, weakness, feelings of anxiety, vomiting, pupillary constriction, convulsions, respiratory distress or labored breathing, unconsciousness, muscle cramp, excessive salivation, respiratory failure, and coma.

LIQUID: POISONOUS IF SWALLOWED. Irritating to skin and eyes.

roducers, formulators and applicators of this nonsystemic pesticide and acaricide. Diazinon is used in the United States on a wide variety of agricultural crops, ornamentals, domestic animals; lawns and gardens; and household pests.

Not flammable. POISONOUS GASES ARE PRODUCED WHEN HEATED. Oxides of sulfur and of phosphorus are generated in fires.

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Speed in removing material from skin is of extreme importance. Shampoo hair promptly if contaminated. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. Effects may be delayed; medical observation is recommended.

UN2783 Organophosphorus pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials.

Reaction with nitrosating agents (e.g., nitrites, nitrous gases, nitrous acid) capable of releasing carci- nogenic nitrosamines. Hydrolyzes slowly in water and dilute acid. Reacts with strong acids and alkalis with possible forma- tion of highly toxic tetraethyl thiopyrophosphates. Incompatible with copper-containing compounds. Contact with oxidizers may cause the release of phosphorous oxides. Contact with strong reducing agents, such as hydrides; may cause the formation of flammable and toxic phosphine gas.

Diazinon is hydrolyzed in acid media about 12 times as rapidly as parathion, and at about the same rate as parathion in alkaline media. In excess water this compound yields diethylthiophosphoric acid and 2-isopropyl-4-methyl-6-hydroxypyrimidine. With insufficient water, highly toxic tetraethyl monothiopyropho- sphate is formed. Therefore, incineration would be a prefer- able ultimate disposal method with caustic scrubbing of the incinerator effluent . In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by follow- ing package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.

A cholinesterase inhibitor; a nonsystemic organophosphate insecticide.

Diazinon is used to control a wide range of sucking and chewing insects and mites in a very wide range of crops and is also used as a veterinary ectoparasiticide.

insecticide, cholinesterase inhibitor

Insecticide.

Nonsystemic contact insecticide used against flies, aphids and spider mites in soil, fruit, vegetables and ornamentals.

ChEBI: A member of the class of pyrimidines that is pyrimidine carrying an isopropyl group at position 2, a methyl group at position 6 and a (diethoxyphosphorothioyl)oxy group at position 4.

Insecticide, Acaricide: Diazinon is the most widely used pesticide by homeowners on lawns, and is one of the most widely used pesticide ingredients for application around the home and in gardens. It is used to control insects and grub worms. It is a nonsystemic organophosphate insecticide used to control cockroaches, silverfish, ants, and fleas in residential, non-food buildings. Bait is used to control scavenger yellow jackets in the western U.S. It is used on home gardens and farms to control a wide variety of sucking and leaf-eating insects. It is used on rice, fruit trees, sugarcane, corn, tobacco, potatoes and on horticultural plants, and is also an ingredient in pest strips. Diazinon has veterinary uses against fleas and ticks. It is available in dust, granules, seed dressings, wettable powder, and emulsifiable solution formulations. In 1988, there were 500 different products containing diazinon on the market, and used in such products as agricultural sprays and granules, animal ear tags, household sprays and dust and veterinary products. Not approved for use in EU countries. A U.S. EPA restricted Use Pesticide (RUP). The U.S. EPA initiated a program to phase out all non-agricultural uses of diazinon commencing in March, 2001. Many commercial outdoor uses of diazinon have been canceled or restricted to licensed pesticide applicators because of its known toxicity to birds and aquatic life. Diazinon is highly toxic to bees and very highly toxic to birds, fish and aquatic invertebrates. Diazinon was canceled for use on golf courses and sod farms in 1988 because of its high risk to birds

AG-500®; AI3-19507®; ALFA-TOX®[C]; ANTIGAL®; ANTLAK®; BASUDIN®; BAZUDEN®; CASWELL No. 342®; DACUTOX®; DASSITOX®; DAZZEL®; DIAGRAN®; DIANON®; DIATERR-FOS®; DIAZAJET®; DIAZATOL®; DIAZIDE®; DIAZINON AG 500 WBC®; DIAZINONE®; DIAZITOL®; DIAZOL®; DICID®; DIMPYLATE®; DIPOFENE®; DIZIKTOL®; DIZINON®[C]; DRAWIZON®; DYMET®; DYZOL®); D.Z.N.®; EXODIN®; FEZUDIN®; FLYTROL®; G 301®; G-24480®; GALESAN®; GARDENTOX®; GEIGY 24480®; KAYAZINON®; KAYAZOL®; NEOCIDOL® (OIL); NEOCIDOL®; NIPSAN®; NUCIDOL®; OLEODIAZINON®; ROOT GUARD; SAROLEX®[C]; SPECTRACIDE®; SROLEX®; SUZON®

Among 23,106 male applicators participating in the Agricultural Health Study who reported using diazinon, there was an increased risk with exposure to diazinon for lung cancer, leukemia, and all cancer sites combined, although the small number of cases observed makes these estimates unreliable .

Biological. Sethunathan and Yoshida (1973a) isolated a Flavobacterium sp. (ATCC 27551) from rice paddy water that metabolized diazinon as the sole carbon source. Diazinon was readily hydrolyzed to 2-isopropyl-4-methyl-6-hydroxypyrimidine under aerobic conditions but less rapidly under anaerobic conditions. This bacterium as well as enrichment cultures isolated from a diazinon-treated rice field mineralized the hydrolysis product to carbon dioxide (Sethunathan and Pathak, 1971; Sethunathan and Yoshida, 1973). Rosenberg and Alexander (1979) demonstrated that two strains of Pseudomonas grew on diazinon and produced diethyl phosphorothioate as the major end product. The rate of microbial degradation increased in the presence of an enzyme (parathion hydrolase), produced by a mixed culture of Pseudomonas sp. (Honeycutt et al., 1984).
Soil. Hydrolyzes in soil to 2-isopropyl-4-methyl-2-hydroxypyrimidine, diethylphosphorothioic acid, carbon dioxide (Getzin, 1967; Lichtenstein et al., 1968; Sethunathan and Yoshida, 1969; Sethunathan and Pathak, 1972; Bartsch, 1974; Wolfe et al., 1976; Somasundaram and Coats, 1991) and tetraethylpyrophosphate (Paris and Lewis, 1973). The half-life of diazinon in soil was observed to be inversely proportional to temperature and soil moisture content (Getzin, 1968). Seven months after diazinon was applied on a sandy loam (2 kg/ha), only 1% of the total applied amount remained and 10% was detected in a peat loam (Suett, 1971).
The reported half-life in soil is 32 days (Jury et al., 1987). Reported half-lives in soil following incubation of 10 ppm diazinon in sterile sand loam, sterile organic soil, nonsterile sandy loam and nonsterile organic soil are 12.5, 6.5, <1 and 2 weeks, respectively (Miles et al., 1979). The reported half-life of diazinon in sterile soil at pH 4.7 was 43.8 days (Sethunathan and MacRae, 1969). Major metabolites identified were diethyl thiophosphoric acid, 2-isopropyl-4-methyl-6-hydroxypyrimidine and carbon dioxide (Konrad et al., 1967). When soil is sterilized, the persistence of diazinon increased more so than changes in soil moisture, soil type or rate of application (Bro-Rasmussen et al., 1968). The halflives for diazinon in flooded soil incubated in the laboratory ranged from 4 to 17 days with an average half-life of 10 days (Sethunathan and MacRae, 1969; Sethunathan and Yoshida, 1969; Laanio et al., 1972). The mineralization half-life for diazinon in soil was 5.1 years (Sethunathan and MacRae, 1969; Sethunathan and Yoshida, 1969).
The half-lives of diazinon in a sandy loam, clay loam and an organic amended soil under nonsterile conditions were 66–1,496, 49–1,121 and 14–194 days, respectively, while under sterile conditions the half-lives were 57–1,634, 46–1,550 and 14–226 days, respectively (Schoen and Winterlin, 1987).
In a silt loam and sandy loam, reported Rf values were 0.86 and 0.88, respectively (Sharma et al., 1986).
Surface Water. In estuarine water, the half-life of diazinon ranged from 8.2 to 10.2 days (Lacorte et al., 1995).
Groundwater. According to the U.S. EPA (1986) diazinon has a high potential to leach to groundwater.
Plant. Diazinon was rapidly absorbed by and translocated in rice plants. Metabolites identified in both rice plants and a paddy soil were 2-isopropyl-4-methyl-6-hydroxypyrimidine (hydrolysis product), 2-(1¢-hydroxy-1¢-methyl)ethyl-4-methyl-6-hydroxypyrimidine and other polar compounds (Laanio et al., 1972). Oxidizes in plants to diazoxon (Ralls et al., 1966; Laanio et al., 1972; Wolfe et al., 1976) although 2-isopropyl-4-methyl- 6-pyrimidin-6-ol was identified in bean plants (Kansouh and Hopkins, 1968) and as a hydrolysis product in soil (Somasundaram et al., 1991) and water (Suffet et al., 1967). Five days after spraying, pyrimidine ring-labeled 14C-diazinon was oxidized to oxodiazinon which was then hydrolyzed to 2-isopropyl-4-methylpyrimidin-6-ol which in turn, was further metabolized to carbon dioxide (Ralls et al., 1966). Diazinon was transformed in field-sprayed kale plants to form hydroxydiazinon {O,O-diethyl-O-[2-(2¢-hydroxy-2¢-propyl)- 4-methyl-6-pyrimidinyl] phosphorothioate} which was not previously reported (Pardue et al., 1970).

The main route of diazinon metabolism in soil, plants and animals is through cleavage of the P-O-pyrimidine group to yield 2-isopropyl-4- methyl-6-hydroxypyrimidine. As with most other phosphorothioates, loss of the pyrimidinyl function in mammalian metabolism probably occurs either through oxidative desulfuration of the thiono group, catalysed by microsomal mixed function oxidases, to give diazoxon followed by hydrolysis catalysed by an A-esterase, or via an oxidative mechanism catalysed by a mixed function oxidase acting directly on diazinon. In the first case the second product is diethyl phosphate and in the second, diethyl phosphorothioate (Yang et al., 1971). Further metabolism then leads to hydroxylation of the methyl and isopropyl groups on the pyrimidine ring. This oxidative metabolism may the act on the pyrimidinol, diazoxon or diazinon itself, the last of which seems to be important in mammalian and avian liver and gives rise to metabolites which still have anticholinesterase or latent anticholinesterase activity.

The main biodegradation pathway in mammals, plants, and soils is pyrimidinyl ester bond cleavage; the principal metabolites are diethyl phosphorothioate and diethyl phosphate. Degradation in the environment involves oxidation to diazoxon and hydrolysis.

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Store in tightly closed containers in a cool, well-ventilated area away from water, and oxidizers, such as peroxides, nitrates, permanganates,chlorates, and perchlorates.

Diazinon(1) is stable at neutral pH but is slowly hydrolysed in alkaline solutions and rapidly at acidic pH values (PM). Hydrolysis products were identified as the pyrimidinol (2) and diethyl phosphorothioate (3) (PSD, 1991).
When diazinon was dissolved in a water/soil suspension and irradiated with UV light, Mansour et al. (1997) demonstrated that one of the products was iso-diazinon (4) formed via a thiono-thiolo rearrangement (see Scheme 1).

The acute oral LD₅₀ for rats and mice are 1250 and 80–135 mg/kg. Inhalation LC50 (4 h) for rats is >2330 mg/m3 air. NOEL (2 yr) for rats is 0.06 mg/kg/d.