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Diazinon

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Introduction

Diazinon is the common name of an organophosphorus insecticide used to control pest insects in soil, on ornamental plants, and on fruit and vegetable field crops. It is also used to control household pests such as flies, fleas, and cockroaches. This chemical is synthetic and does not occur naturally in the environment. Diazinon is sold under common trade names including Alfatox, Basudin, AG 500, Gardentox, Knoxout, and Spectracide.

The pure chemical (100% diazinon) is a colorless and practically odorless oil. Preparations commonly used in insecticides sold in stores are usually 90% diazinon and appear as a pale to dark brown liquid. These preparations have a slight chemical odor but cannot be identified by smell. Diazinon is also used as a seed dressing and is the active ingredient in certain insect baits. Most of the diazinon used is in liquid form, but it is possible to be exposed to the chemical in a solid form. Diazinon does not burn easily and does not dissolve easily in water. It will dissolve in alcohol or other organic solvents such as petroleum products.

Fate & Transport

Diazinon may enter the environment during the manufacturing process, but most environmental contamination comes from agricultural and household application of the chemical to control insects. Diazinon is often sprayed on crops and plants, so small particles of the chemical may be carried away from the field or yard before falling to the ground. Studies have not shown harmful human health effects resulting from airborne contamination of areas surrounding fields where diazinon has been used. After diazinon has been applied, it may be present in the soil, surface waters (such as rivers and ponds), and on the surface of the plants. Diazinon on soil and plant surfaces may also be washed into surface waters by rain. Up to 25% of applied diazinon can return to the air from the surface where it was applied. In the environment, diazinon is rapidly broken down into a variety of other chemicals. Depending on the soil or water conditions, the time required for one-half of the diazinon to be broken down is between a few hours and 2 weeks. Diazinon can move through the soil and contaminate groundwater (water below the surface such as well water). Diazinon is rapidly broken down in the environment and by most animals that eat it. This means the chemical is not likely to build up to high or dangerous levels in animal or plant foods that you might eat.

Exposure Pathways

Small amounts of diazinon have been detected in foods sold to consumers, but studies by the Food and Drug Administration (FDA) have found that the levels in food are far below the level that might cause any harmful health effects. Diazinon has been found in surface and groundwater samples collected at many locations. Only a few of these samples contained high levels of diazinon contamination. These were associated with runoff from contaminated fields or single sources responsible for contamination such such as illegal dumping. In areas surrounding hazardous waste disposal or treatment facilities, you could be exposed by contact with contaminated soils or contaminated runoff water or groundwater that resulted from spills or leaks of material on the site. People who work in the manufacture and professional application of diazinon have the most significant exposure to this pesticide. Other than people who exposed at work, those most likely to be exposed are people who use the chemical at home to spray fruits and vegetables or to control insects in the home.

Metabolism

If you breath air containing diazinon you may absorb it into your body through your lungs. If you eat food or drink water containing diazinon, the chemical may be absorbed from your stomach and intestines. Diazinon may also enter your body across the skin. People living near hazardous waste sites are most likely to be exposed to diazinon through contact with contaminated soil or runoff water. Once in the body, diazinon is rapidly broken down and eliminated from the body in both the urine and feces. Diazinon has not been shown to accumulate in any tissues and almost all of the chemical is eliminated from the body in 12 days.

Health Effects

Most cases of unintentional diazinon poisoning in people have resulted from short exposures to very high concentrations of the material. Usually this occurs when workers who use the chemical do not properly protect themselves, and when they inhale, swallow, or contaminate their skin with a large amount of diazinon. Diazinon affects the nervous system. Some mild symptoms of exposure are headache, dizziness, weakness, feelings of anxiety, constriction of the pupils of the eye, and not being able to see clearly. More severe symptoms include nausea and vomiting, abdominal cramps, slow pulse, diarrhea, pinpoint pupils, difficulty breathing, and passing out (coma). These signs and symptoms may start to develop within 30-60 minutes and reach their maximum at about 6-8 hours. Very high exposure to diazinon has resulted is death in people accidently exposed in those who have swallowed large amounts of the chemical to commit suicide. Acute pancreatitis has developed in some people and in laboratory animals exposed to large amounts of diazinon. Longer exposure to lower levels of diazinon has also been reported to produce some of these symptoms in exposed workers and in people living in houses recently treated with the chemical to control pests. In almost all cases, complete recovery occurred when exposure stopped. There is no evidence that long-term exposure to low levels of diazinon causes any harmful health effects in people. Diazinon has not been shown to cause birth defects or to prevent conception in humans. The International Agency for Research on Cancer, the Environmental Protection Agency, and the National Toxicology Program have found no evidence that diazinon causes cancer in people or animals. However, more studies are being conducted.

Information excerpted from:

Toxicological Profile for Diazinon August 1994 Draft

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services

Structural diagram:

National Institutes of Health