DIAZINON

Chemical Name:           

Category : Organophosphate

Physical Properties

CAS Number: 333-41-5

Description: Diazinon is a colorless to dark brown liquid. It has a flashpoint of 180 F

Molecular formula:  C₁₂H₂₁N₂O₃PS

Molecular weight: 304.35

Melting point: decomposes  >120 C

Solubility: water - 40 mg/L @ 20 C, Miscible in organic solvents

Vapour Pressure: 0.097 mPa @ 20 C

Usage :

Diazinon is a persistent, broad spectrum organophosphate insecticide used on a wide variety of crops and plants to control sucking and leaf eating insects. It is also used for the control of insects on stock (lice and ticks) particularly, fly strike on sheep. 

In the home diazinon is often used as an ant killer and for the control of fleas and ticks on domestic pets.

Regulatory Status:

 TWA: 0.1 mg/m3

 STEL: no guideline

 ACGIH TLV: TWA 0.1 mg/m3                       (8)

In the United States,  Diazinon is classified as a Restricted Use Pesticide (RUP) and is for professional pest control operator use only. In 1988, US EPA canceled registration of diazinon for use on golf courses and sod farms because of die offs of birds that often congregated in these areas.(10)

HEALTH EFFECTS:

Acute Toxicity

As an organophosphate, Diazinon inhibits the enzyme, acetylcholinesterase and causes depression of the Central Nervous System. It is easily absorbed through the skin. Ingestion or inhalation may cause headaches, giddiness, blurred vision, confusion, weakness, cramps, diarrhea, respiratory problems, sweating, vomiting, muscle twitches, convulsions, coma, renal or hepatic damage. (4) (5)

Fatal dose in man estimated to be 360mg/kg.  (6)

Diazinon is classified as slightly toxic to moderately toxic depending on the formulation. Diazinon itself is not a potent cholinesterase inhibitor. However, in animals, it is converted to diazoxon, a compound that is a strong enzyme inhibitor. (10)

Chronic Toxicity

Chronic exposure may result in above symptoms plus frontal lobe impairment.  (4)

No-effect doses have ranged from 0.02 mg/kg/day in humans to 0.1 mg/kg/day in rats. These values are based on inhibition of the enzyme acetylcholinesterase. Enzyme inhibition has been documented in red blood cells, in blood plasma, and in brain cells at varying doses and with different species (10).

Chronic effects have been observed at doses ranging from10 mg/kg/day for swine to 1,000 mg/kg/day for rats. These effects included only visibly recognisable symptoms of toxicity (gross toxicities). Certain effects such as the inhibition of red blood cell cholinesterase, and enzyme response occurred at much lower doses in the rats.(10)

Carcinogenicity:

Based on animal tests Diazinon does not appear to be carcinogenic.

Diazinon has not been evaluated by International Agency for Research on Cancer. (2)

Mutagenicity:

Chromosone aberrations were produced in human lymphocytes at a dose of 0.5mg/l   (6)

Teratogenicity and Reproductive effects:

The data on reproductive and developmental effects due to chronic exposure is limited. (10)

An experimental teratogen and experimental reproductive effects (1)

Fate in humans :

The half-life of diazinon in animals is about 12 hours. The product is passed out of the body through urine and in the feces. The metabolites account for about 70% of the total amount excreted. (10)

ACTION ON ANIMALS

Diazinon has a high to very high freshwater fish acute toxicity.

Freshwater Fish Acute Toxicity Coldwater

                      LC50 90ug/l (Rainbow Trout) (2)

There is some evidence that saltwater fish are more susceptible than freshwater fish.

Bioconcentration ratios range from 200 in minnows to 17.5 for guppies (10)

Diazinon is very highly toxic to birds. (2)

                Avian acute toxicity 6.3mg/kg (Mallard Duck)

                Avian dietary toxicity <47ppm (Mallard Duck)

                Honey Bees Contact LD 50 0.22ug

The US EPA in 1988 concluded that the use of diazinon in turf and golf course treatment poses a "widespread and continuous hazard" to birds. (10)

 Two mice studies indicate Diazinon is not carcinogenic.(2)

Rabbit and rat studies showed no developmental toxicity up to and including dose 100mg/kg. (2)

Tests with Rabbits and hamsters were negative for teratology but tests with chicks produced congenital malformations.  (6)

Diazinon injected into chicken eggs resulted in skeletal and spinal deformities in the chicks. Bobwhite quail born from eggs treated in a similar manner showed skeletal deformities but no spinal abnormalities but Acetylcholine was significantly affected. (10)

Tests with dogs and pigs at higher levels (1.0 10.0 mg/kg/day) revealed gross abnormalities (10)

Cattle exposed to diazinon may store it in their fat for a short term. One study showed that the cows excreted the compound within 2 weeks after spraying stopped. (10)

In plants, a lower temperature and a high oil content tend to increase the persistence of diazinon. Generally the half-life is rapid in leafy vegetables, forage crops and grass, ranging from two days to 14 days. Diazinon is absorbed by plant roots when applied to the soil and translocated to other parts of the plant (10).

ENVIRONMENTAL FATE

Diazinon is persistent in the soil for approximately 12 weeks.  The major soil degradate, oxypyrimidine is more persistent than the original compound. (2)  Diazinon is not expected to bind to soil and but exhibit moderate mobility. Biodegradation is major fate process with half life of <1 - 5 weeks in non sterile soils and half lives of 6 - 12.5 weeks in  sterile soils.  (9)

Diazinon seldom migrates below the top 1.3 centimetres in soil but can stay biologically available for six months under conditions of low temperature and low moisture. The average time for 50% degradation in soil is two to four weeks. (10)

The breakdown rate is dependent on the acidity of water. At highly acidic levels, one half of the

compound disappeared within 12 hours while in a neutral solution, the pesticide took six months to degrade to one half of the original concentration (10).

When released to water, diazinon may sorb to sediments moderately but should not significantly bioconcentrate in aquatic organisms. Reported half lives in water (20C): 31 days- pH 5, 185 days- pH 7.4, 136 days- pH 9. Volatilisation from water can be important transport process. In sampling of US surface and ground water Diazinon was detected in 6,026 of 22,291 surface water samples from 3,555 locations with a maximum concentration of 33,400ug/l.  It was also detected in 74 of the 3,633 ground water samples taken in 2,835 locations.  The maximum concentration in ground water was 84ug/l. (3)

When released to atmosphere, it is expected to survive in vapour phase (expected half-life: 4.1 hours) and particulate phase.  Detected in 61% of 787 ambient air samples from 14 states in 1970 US National Monitoring Programs, max concentration was 62.2 ng/m3,  average: 3.0 ng/m3. (9)

FURTHER INFORMATION

US EPA identified 5 major data gaps including toxicology, environmental fate and effects, and residue chemistry.  (2)

International Organisation of Consumers Union (IOCU) warns of the possibility of the highly toxic contaminant Sulfotepp in old stock, particularly opened containers.IOCU recommends the removal of children and animals from area for 4

 hours after spraying.  (7)

* Disclaimer: These sheets are designed as summary information and as such

are a guide only.

References:

1.Irving Sax, N. & Lewis, R.J. “Dangerous Properties of Industrial Materials” Seventh Edition , Van Nostrand Reinhold 1989 N.Y. USA

2.EPA Pesticide Fact Sheet, Diazinon 1988

3.EPA Health Advisory, Office of Drinking Water US EPA Aug 1988

4.Pesticides and Human Health, W.H.Hallenbeck&K.M.Cunningham-Burns School

  of Public Health, University of Illinois Chicago, Springer-Verlag

5.Chemical Hazard Response Information System, US Dept. of Transportation.

6.Oil & Hazardous Materials - Technical Assistance Data System, US EPA

7.The Pesticide Handbook, Profiles for Action. International Organisation

  of Consumers Union, 1986

8. Exposure Standards for Atmospheric Contaminants in the Occupational Environment

    [NOHSC:3008(1995)] http://www.nohsc.gov.au/databases/exp/az/Diazinon.htm

9.Handbook of Environmental Fate and Exposure Data for Organic Chemicals,

  Ed. P.H.Howard  Lewis Pub. Michigan 1991

10. E X T O X N E T, Extension Toxicology Network Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program available at http://ace.orst.edu/cgi-bin/mfs/01/pips/