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| WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE ORGANIZATION ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION ET L'AGRICULTURE
VBC/DS/79.45 ORIGINAL: ENGLISH
DIAZINON
It must be noted that the issue of a Data Sheet for a particular pesticide does not imply endorsement of the pesticide by WHO or FAO for any particular use, or exclude its use for other purposes not stated. While the information provided is believed to be accurate according to data available at the time when the sheet was compiled, neither WHO nor FAO are responsible for any errors or omissions, or any consequences therefrom.
The issue of this document does Ce document ne constitue pas une not constitute formal publication. Il ne doit faire publication. It should not be l'objet d'aucun compte rendu ou reviewed, abstracted or quoted résumé ni d'aucune citation sans without the agreement of the l'autorisation de l'Organisation Food and Agriculture des Nations Unies pour Organization of the United l'Alimentation et l'Agriculture Nations or of the World Health ou de l'Organisation Mondiale de Organization. la Santé.
CLASSIFICATION:
Primary use: Insecticide
Secondary uses: Ectoparaiticide Namaticide
Chemical group: Organophosphorus compound
Date issued: April 1979
1. GENERAL INFORMATION
1.1 COMMON NAME: Diazinon (ISO)
1.1.1 Identity: O,O-diethyl 0-[6-methyl-2-(1-methylethyl)-4-pyrimidinyl] phosphorothioate
1.1.2 Synonyms: G.24480 BasudinR DianonR KayazinonR Necidol/NucidolR
Local synonyms:
1.2 SYNOPSIS - An organophosphorus pesticide of moderate mammalian toxicity. It may be absorbed by all routes of exposure; it is active upon metabolism and not cumulative in body tissues.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics - When pure, it is a colourless oil of b.p. 83°-84°C at 0.002 torr. The technical product is a pale to dark brown liquid of at least 95% purity.
1.3.2 Solubility - Its solubility in water at room temperature is 40 mg/l. It is miscible with ethanol, acetone, zylene and is soluble in petroleum oils.
1.3.3 Stability - Diazinon decomposes above 120°C and is susceptible to oxidation. It is stable in alkaline media, but is slowly hydrolysed by water and by dilute acids. The presence of traces of water promotes hydrolysis on storage to highly toxic tetraethyl monothiopyrophosphate.
1.3.4 Vapour pressure (volatility) - low: 1.4 x 10-4 torr at 20°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations - ULV concentrates, wettable powders 40%; emulsifiable concentrates 60%, 40% and 25%; dusts 2-4%; granules 3-14%, aerosols 20%.
1.4.2 Susceptible pests - House-flies, ticks on cattle, blowflies and mites on sheep, wide range of sucking and leaf eating insects on crops; diptera in glasshouses.
1.4.3 Use pattern - Main applications are in rice, fruit, vineyards, sugar-cane, corn, tobacco, potatoes, horticultural crops, animal dips and sprays.
1.4.4 Unintended effects - Can damage maidenhair fern, cucumber and tomatoes if applied before mid May.
1.5 PUBLIC HEALTH PROGRAMME
1.6 HOUSEHOLD USE: Used by trained pest control operators in
households and outbuildings to control cockroaches, ants, silverfish, spiders, carpet beetles and scorpions.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption routes - May be absorbed by the intact skin as well as by inhalation and from the gastrointestinal tract.
2.1.2 Mode of action - Cholinesterase inhibition after conversion to the oxygen analogue diazoxon.
2.1.3 Excretion products - After an oral dose, rats excrete diazinon and its metabolites mainly in the urine; 95-98% of an oral dose is excreted in 168 hours.
2.1.4 Toxicity, single dose
Oral: LD50 rats: 300-850mg/kg - varies with stability of product. Lower value adopted for classification purposes.
Dermal: LD50 rats: 2150 mg/kg Most susceptible species: No infomation.
2.1.5 Toxicity, repeated doses
Oral: See 2.1.6, dietary studies, short-term.
Cumulation of compound: Diazinon and its metabolites are rapidly excreted from the body, mainly in urine.
Cumulation of effect: Repeated exposures to diazinon may have a cumulative effect on cholinesterase levels.
2.1.6 Dietary studies
Short-term: Rats fed diazinon in the diet at 100 and 1000 mg/kg diet for four weeks exhibited no toxic symptoms except a slight inhibition of growth, a distinct inhibition of erythrocyte cholinesterase and some inhibition of brain cholinesterase at 1000 mg/kg. No significant inhibition of plasma cholinesterase was found at either concentration. Dogs and pigs were orally administered diazinon by capsule daily for periods of up to eight months. Doses for pigs were 0, 1.25, 2.5, 5 and 10 mg/kg bw; for dogs 0, 2.5, 5, 10 and 20 mg/kg bw. In pigs mortality and cholinergic signs of poisoning were evident at 2.5 mg/kg per day and above, and in dogs, above 10 mg/kg.
Long-term: Two groups of weanling rats (20 males and 20 females) and one group of 20 males were fed for 72 weeks on diets containipg 10, 100 and 1000 mg/kg diet of diazinon as a 25% wettable powder. At 1000 mg/kg some inhibition of growth was observed. No macroscopic or histological lesions were observed at autopsy.
A group of 3 males and 3 female monkeys were given daily oral doses of 0.05, 0.5 and 5.0 mg/kg bw diazinon for two years. No significant inhibition of erythrocyte or plasma cholinesterase was found at the 0.05 mg/kg/day level. This did occur at higher levels and was dose related.
2.1.7 Supplementary studies of toxicity
Teratogenicity: Oral administration of diazinon in maize oil at a dose of 0.125 mg/kg bw on day 6, 7 and 8 of gestation and at 2.25 mg/kg on day 7 or 8 produced no terata in the hamster. Administration of diazinon to rabbits daily from day 5-15 of gestation at 7 or 30 mg/kg bw per day, induced no terata or dose-related embryo toxic effects.
Mutagenicity: In one test in vitro, diazinon applied at high concentrations, was considered to have a mutagenic effect on human lymphocytes. However, a dominant lethal test on male mice given single doses of 15 and 45 mg/kg bw was negative. In vitro tests on E. coli systems were also negative.
2.1.8 Modification of toxicity - Raising the protein content of feed from 29% to 81% or lowering it to 4% increased the acute toxicity of diazinon to rats approximately twofold.
2.2 TOXICOLOGY - MAN
2.2.1 Absorption - Diazinon may be absorbed readily through the intact skin, from the gastrointestinal tract or by inhalation.
2.2.2 Dangerous doses
Single: Not known. A man swallowed a quantity of 30 mg/kg of diazinon without any detrimental effect on health. Another man who took 250 mg/kg recovered after treatment.
Repeated: No information (see 2.2.5 "observations on volunteers").
2.2.3 Observations of occupationally exposed workers - Slight asymptomatic reduction in cholinesterase activity has been found in spraymen as a result of extensive occupational exposure to diazinon.
2.2.4 Observations on exposure of the general population - With good agricultural practice, the general population should not be exposed to hazardous amounts of diazinon.
2.2.5 Observations of volunteers - Volunteers have been given in separate experiments, oral doses of diazinon at 0.025 mg/kg bw for 5 days, 0.025-0.03 mg/kg for 32-34 days, 0.05 mg/kg for 5 days, then allowed to recover for 23 days; this was followed by 0.05 mg/kg for a further 5 days, 0.025 mg/kg for 43 days and 0.02 mg/kg for 37 days. Under none of these dosing regimens was an effect on haematology, liver function or urine analysis observed, nor were any symptoms experienced. Slight reduction of plasma cholinesterase activity was observed with all dosing schedules, but no effect was seen on erythrocyte cholinesterase.
2.2.6 Reported mishaps - Contamination of doughnut mix due to spillage during storage resulted in 20 cases of poisoning with diazinon, none of which was fatal. Eight children were poisoned in two separate incidents by eating grain treated with diazinon.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES
2.3.1 Fish - Toxic
2.3.2 Birds - Very highly toxic (mallards and pheasants LD50 2-6 mg/kg)
2.3.3 Other species - Toxic to bees and livestock.
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(For definition of categories see Introduction to data sheets)
Liquids over 20%; category 3. Other liquids, solids over 50%; category 4 all other solids: category 5.
3.2 TRANSPORTATION AND STORAGE
Formulations in Categories 3 and 4 should be transported and stored in clearly labelled rigid and leakproof containers, away from containers of food and drink. Storage should be under lock and key and secure from access by unauthorized persons and children.
Formulations in Category 5 should be transported and stored
in clearly labelled leakproof containers, out of reach of children, away from food and drink.
3.3 HANDLING
Formulations in Categories 3 and 4 - Protective clothing (see part 4) should be used by all handling of the compound. Adequate washing facilities should be available at all times during handling and should be close to the site of handling. Eating, drinking and smoking should be prohibited during handling and before washing after handling.
Formulations in Category 5 - The same facilities required as those needed for the handling of any chemical.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS
All formulations - Containers may be decontaminated (for method see paragraph 4.3). Decontaminated containers should not be used for food and drink. Containers that are not decontaminated should be burned or crushed and buried below topsoil. Care must taken to avoid subsequent contamination of water sources.
3.5 SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS
Formulations in Categories 3 and 4 - Pre-employment medical examination of workers desirable. Workers suffering from active hepatic or renal disease should be excluded from contact. Pre-employment and periodic cholinesterase test for workers desirable especially for those handling concentrates. Special account should be taken of the workers' mental ability to comprehend and follow instructions. Training of workers in techniques to avoid contact essential.
Formulations in Category 5 - Warning of workers to minimize contact essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
All formulations - Pilot and loaders should have special training in application methods and early symptoms of poisoning, and must wear a suitable respirator. Flagmen, if used, should wear overalls and be located well away from the dropping zone.
3.7 LABELLING
Formulations in Categories 3 and 4 - Minimum cautionary statement - Diazinon is an organophosphorus compound that
inhibits cholinesterase. It is poisonous if swallowed. It may be absorbed through the skin. Avoid skin contact; wear hand protection, clean protective clothing and a respirator when handling the material. Wash thoroughly with soap and water after using. Keep the material out of reach of children and well away from foodstuffs, animal feed and their containers. If poisoning occurs, call a physician. Atropine and pralidoxime are specific antidotes and artificial respiration may be needed.
Formulations in Category 5 - Minimum cautionary statement - This formulation contains diazinon which is a toxic substance. Keep the material out of reach of children and well away from foodstuffs, animal feeds and their containers.
3.8 RESIDUES IN FOOD
Maximum residue limits have been recommended for diazinon by the Joint FAO/WHO Meeting on Pesticide Residues. These are subject to change at annual reviews.
4. PREVENTION OF POISONING IN MAN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
4.1.1 General - Diazinon is an organophosphorus pesticide of moderate toxicity. It is readily absorbed through the intact skin, from the gastrointestinal tract and by inhalation. Repeated exposure may have a cumulative effect on cholinesterase levels.
4.1.2 Manufacture and formulation - TLV: 1 mg/m3 (FRG). Closed systems and forced ventilation may be required to reduce as much as possible the exposure of workers to the chemical.
4.1.3 Mixers and applicators - When opening the container and when mixing, protective impermeable boots, clean overalls, gloves and respirator should be worn. Mixing if not mechanical, should always be carried out with a paddle of appropriate length. When spraying tall crops or during aerial application, a face mask should be worn, as well as an impermeable hat, clothing, boots and gloves. The applicator should avoid working in spray mist and avoid contact with the mouth. Particular care is needed when equipment is being washed after use. All protective clothing should be washed immediately after use, including the insides of gloves. Splashes must be washed immediately from the skin, or eyes with large quantities of water. Before eating, drinking, or smoking, hands and other exposed skin should be washed.
4.1.4 Other associated workers (including flagmen in aerial operations) - Persons exposed to diazinon and associated with its application should wear protective clothing and observe the precautions described above in 4.1.3 under "mixers and applicators".
4.1.5 Other populations likely to be affected - With good application practice, subject to 4.2 below, other persons should not be exposed to hazardous amounts of diazinon.
4.2 ENTRY OF PERSONS INTO TREATED AREAS - Unprotected persons should be kept out of treated citrus, and store fruit areas and vineyards for five days and out of other treated areas for at least one day.
4.3 DECONTAMINATION OF SPILLAGE AND CONTAINERS - Residues in containers should be emptied in a diluted form into a deep pit, taking care to avoid ground waters. The empty container may be decontaminated by rinsing two or three times with water and scrubbing the sides. An additional rinse should be carried out with 5% sodium hydroxide solution which should remain in the container overnight. Impermeable gauntlets should be worn during this work, and a soakage pit should be provided for the rinsings. Decontaminated containers should not be used for food and drink. Spillage of diazinon and its formulations should be removed by washing with 5% sodium hydroxide solution and then rinsing with large quantities of water.
4.4 EMERGENCY AID
4.4.1 Early symptoms of poisoning - Early symptoms of poisoning may include excessive sweating, headache, weakness, giddiness, nausea, vomiting, hypersalivation, stomach pains, blurred vision, slurred speech and muscle twitching. Later there may be convulsions, and coma.
4.4.2 Treatment before person is seen by a physician, if these symptoms appear following exposure - The person should stop work immediately, remove contaminated clothing and wash the affected skin with soap and water, if available, and flush the area with large quantities of water. If swallowed, and if the person is conscious, vomiting should be induced. In the event of collapse, artificial respiration should be given, bearing in mind that if mouth-to-mouth respiration is used, vomit may contain toxic amounts of diazinon.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING
5.1.1 General information - Diazinon is an organophosphorus pesticide of moderate mammalian toxicity which is active against a variety of agricultural and public health pests. It is readily absorbed by the gastrointestinal tract, through the intact skin and by inhalation. It is converted in vivo to the oxygen analogue diazixon which then inhibits cholinesterase. It does not accumulate in body tissues.
5.1.2 Symptoms and signs - Initial symptoms of poisoning may include excessive sweating, headache, weakness, giddiness, nausea, hypersalivation, vomiting, stomach pains, blurred vision, slurred speech and muscle twitching. More advanced symptoms of poisoning may be convulsions, coma, loss of reflexes and loss of sphincter control.
5.1.3 Laboratory - The most important laboratory finding is reduction of activity of blood cholinesterases. Urinary levels of organic phosphorus containing metabolites may also be used as a measure for exposure. Neither method is specific for diazinon.
5.1.4 Treatment - If the pesticide has been ingested, rapid gastric lavage should be performed using 5% sodium bicarbonate if available. For skin contact, the skin should be washed with soap and water. If the compound has entered the eyes, they should be washed with large quantities of isotonic saline or water.
Persons without signs of respiratory inefficiency but with manifest peripheral symptoms should be treated with 2-4 mg of atropine sulfate and 1000 mg pralidoxime chloride or 250 mg of toxogonin (adult dose) by slow intravenous injection. More atropine may be given as needed. Persons with severe intoxication with respiratory difficulties, convulsions and unconsciousness should immediately be given atropine and a reactivator. In such severe cases 4-6 mg of atropine sulfate should be given initially followed by repeated doses of 2 mg at 5-10 min intervals. Diazepam may be given to control convulsions. The patient's condition including respiration, blood pressure, pulse frequency, salivation and convulsions should be carefully observed as a guide to further administration of atropine.
The airways should be kept free and artificial respiration should be applied, if required, preferably by mechanical means. If necessary, intubation should be performed.
Contraindications are morphine, barbiturates, other tranquillizers and central stimulants of all kinds.
5.1.5 Prognosis - If the acute toxic effect is survived and adequate artificial respiration has been given, if needed, the chances of complete recovery are good. However, in very severe cases, particularly if artificial respiration has been inadequate, prolonged anoxia may give rise to permanent brain damage.
5.1.6 References of previously reported cases
Willems, J., Vermeire, P. & Rolly, G. (1971) Arch. Toxikol., 28, 182-191 Namba, T. et al. (1971) Amer. J. Med., 50 (4), 475-492 West, I. (1965) Calif. Hlth, p. 11 Hayes, W. J. (1963) Clinical Handbook on Economic Poisons, US Department of Health Education and Welfare
5.2 SURVEILLANCE TESTS
Test Normal Action Symptomatic level* level* level*
Plasma cholinesterase 100% 50% variable
Erythrocyte cholinesterase 100% 70% usually 40%
* Expressed at percentage of pre-exposure activity.
5.3 LABORATORY METHODS
5.3.1 Detection and assay of compound - References are given only,
A method involving conversion of diazinon sulfur to H2S, which is then reacted with dimethyl-P-phenylenediamine and FeCl3 to give methylene blue, and is determined spectrophotometrically at 665 mu is given in:
Analytical methods for pesticides, Plant growth regulators and food additives, Vol. II Insecticides, Academic Press, 1964.
Diazinon, Section 10, p. 109, Margot, A. & Stammbac, K.
A second spectrophotometric method involves conversion of diazinon to pyrimidinol and measurement at 272 mu. See: Blinn, R. C. & Gunther, F. A. (1953) J. Agr. Food Chem.,1 (4), 325.
Methods involving gas liquid chromatography using a thermionic phosphorus detector are given in: Analytical methods for pesticides and plant growth regulators, Vol. VI; Gas chromatographic analysis, edited by Zweig, G., Academic Press, 1972, Section 21, p. 345.
5.3.2 Other tests in cases of poisoning
Levels of cholinesterase in the blood, particularly plasma, provide the most useful diagnosis of poisoning. Michel, N. 0. (1949) J. Lab. Clin. Med., 34, 1564-1568. Ellman, G. L. et al. (1961) Biochem. Pharmacol., 7, 88-95.
Measurement of urine metabolites may also be determined in order to give an indication of exposure for methods. See section 5.3.1, Detection and assay.
See Also: Toxicological Abbreviations Diazinon (EHC 198, 1998) Diazinon (ICSC) Diazinon (FAO Meeting Report PL/1965/10/1) Diazinon (FAO/PL:CP/15) Diazinon (FAO/PL:1967/M/11/1) Diazinon (FAO/PL:1968/M/9/1) Diazinon (AGP:1970/M/12/1) Diazinon (WHO Pesticide Residues Series 5) Diazinon (Pesticide residues in food: 1979 evaluations) Diazinon (Pesticide residues in food: 1993 evaluations Part II Toxicology) Diazinon (JMPR Evaluations 2001 Part II Toxicological) | |
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