Guthion

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Azinphos-methyl

Pesticide Fact Sheet

Prepared for the U.S. Department of Agriculture, Forest Service by Information Ventures, Inc.

Common name: Azinphos-methyl

Chemical name: O,O-dimethyl-s-[(4-oxo-1,2,3-benzotriazin-3(4H)-yl)methyl] phosphoro-dithioate

Common Product names: Guthion®, Gusathion-M®

Pesticide classification: insecticide, acaricide, molluscicide

The contents of two azinphos-methyl formulations are listed below.

Guthion® 50% Wettable Powder: azinphos-methyl (50%), silica (1-5%) and other inert ingredients (45-49%)

Guthion® 3 Flowable: azinphos-methyl (30%) and inert ingredients (70%)

VI. Human Health Effects

Reported effects: Azinphos-methyl inhibits the activity of the enzyme cholinesterase in humans. The degree of inhibition increases with the dose of azinphos-methyl received. Symptoms of azinphos-methyl poisoning include nausea, increased salivation, tearing, blurred vision, vomiting, diarrhea, abdominal cramps, dizziness, and sweating. There may be respiratory symptoms such as wheezing and chest tightness in inhalation exposures. Sweating and muscle twitching may occur in areas of skin exposure. High doses can cause weakness, muscle twitching, confusion, difficulty in walking, slurred speech, convulsions, coma and death. There have been cases of poisoning from exposure to azinphos-methyl which required medical attention or hospitalization. There have been several deaths, including a suicide. Eye and skin injuries requiring medical attention have been reported. Chronic toxicity:

Reported effects: Repeated exposure to low levels of azinphos-methyl can cause the same symptoms seen with acute poisoning. Potential for adverse health effects from contacting or consuming treated vegetation, water or animals: Insufficient information available.

Potential for adverse health effects from inert ingredients contained in the formulated product: Because of concern for human health and the environment, the U.S. Environmental Protection Agency (EPA) announced its policy on inerts of toxicological concern (Lists 1 and 2) in the Federal Register on April 22, 1987 (52 FR 13305). The intent of this policy is to encourage the use in pesticide products of the least toxic inert ingredients available. EPA's strategy for the implementation of this policy included the development of four lists of inert ingredients according to toxicity. The toxicity categories for the lists of inert ingredients are:

List 1 - Inerts of toxicological concern

List 2 - Potentially toxic inerts/high priority for testing

List 3 - Inerts of unknown toxicity for which there is little concern that they will be shown to be toxic

List 4 - Inerts of minimal concern

For pesticides containing List 1 inerts, the EPA has given the pesticide registrant the opportunity to reformulate the product to remove the List 1 inerts. If the registrant chooses not to reformulate the product, then the List 1 inerts must be identified on the product label. For List 2 inerts, the EPA is monitoring ongoing testing and gathering existing information on the potential adverse effects of these chemicals to determine if further regulatory action is required. The EPA has no particular regulatory plans for List 3 and List 4 inerts. The Forest Service will incorporate new data on inerts into updated fact sheets as it becomes available.

No inerts cited on EPA List 1 are included in the Guthion 50% Wettable Powder or Guthion 3 Flowable formulations. Inert ingredients found in azinphos-methyl wettable powder formulations include crystalline silica, an EPA List 4 inert. Laboratory studies in animals and studies on disease incidence in workers have shown that long-term exposure to silica may cause silicosis. Silicosis is a disabling, progressive and sometimes fatal lung disease. There is also some evidence that crystalline silica may be a cancer causing agent.

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