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About Pesticide Tolerances

By law, EPA is responsible for regulating the pesticides that are used by growers to protect crops grown for human food and animal feed and for setting limits on the amount of pesticides that may remain in or on foods marketed in the USA. These limits on pesticides left on foods are called "tolerances" in the United States (they are referred to as maximum residue limits, or MRLs, in many other countries).

EPA establishes tolerances for each crop use of a pesticide after developing a risk assessment that considers:

  • The aggregate, non-occupational exposure from the pesticide (exposure through diet and drinking water and from pesticides used in and around the home).
  • The cumulative effects from exposure to pesticides that have a common mechanism of toxicity (that is, two or more pesticide chemicals or other substances that cause a common toxic effect(s) by the same, or essentially the same, sequence of major biochemical events, interpreted as mode of action).
  • Whether there is increased susceptibility to infants and children or other sensitive subpopulations, from exposure to the pesticide.
  • Whether the pesticide produces an effect in people similar to an effect produced by a naturally occurring estrogen or produces other endocrine disruption-effects.

Some risk assessments use the assumption that residues will always be present in food at the maximum level permitted by the tolerance. Other risk assessments use actual or anticipated residue data, to reflect real-world consumer exposure as closely as possible.

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The U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) enforce tolerances to ensure that the nation's food supply is maintained safely at all times:

  • USDA enforces tolerances established for meat, poultry and some egg products.
  • FDA enforces tolerances established for other foods. 

In August 1996, the Federal Food, Drug, and Cosmetic Act was amended to include the Food Quality Protection Act or FQPA. This Act required EPA to reassess by August 2006 all of the pesticide tolerances that were in place in early August 1996 to ensure that they met current safety standards and were supported by up-to-date scientific data. We completed this reassessment by the deadline and since then, reviews of tolerances have been included in the registration review of pesticides.

Generally during registration review, we review any new data to support tolerance decisions based on:

  • the anticipated residue levels of the pesticide in or on food, as reflected in crop field trial or food processing studies, or
  • the actual levels of the pesticide that have been measured through food monitoring studies and surveillance programs.

Periodically, and depending on the specific pesticide tolerance in question, EPA will reexamine the risk assessments used to set tolerances, to ensure that tolerances accurately reflect actual or anticipated residue levels in foods. This reexamination, in conjunction with a review of other exposure routes for that pesticide (from drinking water and residential uses of the pesticide), will ensure "a reasonable certainty that no harm will result from aggregate exposure."

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