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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 

          Structural formula


    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:
        Diazinon (ICSC)
        Diazinon (PIM 182)