Guthion -- EPA Technical Summary for Azinphos-methyl

EPA is scheduled to  hold a public meeting and technical briefing on May 19, 1999.  The following appeared on their web site (  as of May18th: 


  • Azinphos-methyl is used on a wide variety of fruit and vegetable crops, tree crops,  grains, cotton, and ornamentals.
  • Azinphos-methyl is a restricted use pesticide applied aerially and by ground methods.
  • On average, two million pounds of azinphos-methyl are applied annually.

Health Effects

  • Azinphos-methyl can cause cholinesterase inhibition in humans; that is, it can overstimulate the nervous system causing nausea, dizziness, confusion, and at high exposures, respiratory paralysis and death.


Dietary Risk is high from acute exposure.

  • The acute risk assessment is highly refined using USDA Pesticide Data Program (PDP) data, that reflects actual use of pesticides and FDA monitoring for most commodities.
  • At the 99.9th percentile, acute risks for infants and children are of concern. At the 99.8th percentile, risk for the general population and all  subpopulations is not of concern. At the 99.9th percentile, the risk is not driven by an individual with an extreme consumption pattern nor by an unusual residue level.
  • Apple consumption is clearly the major contributor to risk followed by peaches and pears. All scenarios evaluated that include apples result inacute risk which is of concern to at least one subpopulation. Without apples, acute risk to all subpopulations is not of concern at the 99.9th percentile.                     
  • Chronic risk is not a concern.

Worker Risk is very high.

  • For mixers, loaders, and applicators, risks for most exposure scenarios evaluated are of concern even with maximum PPE/engineering controls. For exposure scenarios which have risks of concern, estimated MOEs range from <1 to 90.
  • For most crops,post-application risk, at the current restricted entry intervals (REIs), is of concern. For many crops, to achieve risk estimates that are not  of concern, REIs would be too long to be practical for crop production.

Drinking Water Risk is uncertain.

  • Acute exposure will add to the dietary risk, which is already a risk concern.
  • Chronic exposure does not appear to be of concern.

Aggregate Risk is of concern from acute exposure.

  • Aggregate acute risk is of concern because food alone is of concern and  water will only make the exceedance larger.
  • Aggregate chronic risk (food and water) is not of concern.

Ecological Risks are high.

  • The preliminary risk assessment indicates that risk to aquatic organisms is very high and risk to terrestrial organisms is also of concern.

How the Risk Picture May Change

  • An apple cooking study on baby food could reduce the estimated dietary risk.


For additional information on EPA's summary contact: Chemical Review Manager,  Barry O'Keefe,;      703-308-8035.

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