The Environmental Protection Agency says it will define a one-in-million chance of getting cancer as effectively zero, permitting it to sometimes disregard a legal provision that outlaws cancer-causing additives in food.

Paradoxically, the agency says this could reduce the pesticide threat in the diet by speeding the introduction of pesticides that are weak causes of cancer but safer than those being used today.Though EPA doesn't regulate most food additives, it does regulate pesticides. Federal law defines as an additive any pesticide residue on food that is concentrated by processing.

A cancer-causing residue may be permitted on raw food if EPA finds that the benefit of pesticide use outweighs the risk.

When the federal Food, Drug and Cosmetic Act of 1958 was passed, it included a provision, called the "Delaney clause" after the bill's main sponsor, then-Rep. James J. Delaney, D-N.Y., banning any food additive shown to cause cancer in man or animal.

Up to now, EPA has interpreted the clause to require it to refuse to establish a permitted residue level for new cancer-causing pesticides that become more concentrated during processing, and to refuse to issue pesticide licenses for such new chemicals.

But in the early 1980s the agency became aware that new data gathered in its massive review of old pesticides licensed under looser standards would forbid the licensing of those chemicals if they were to come up again.

Jack Moore, the agency's acting deputy administrator, admitted to reporters Wednesday that the agency was reluctant to face the implications of the new data at first.

Even today, a "zero risk (policy) is totally infeasible as we sit here . . . There would be so many pesticide uses being curtailed we'd cause dramatic and deep disruption in the food supply," Moore said.

Moore said the policy change will permit EPA to decide the fate of 73 currently licensed old pesticides for which there is some evidence of cancer-causing power.

There are at least a dozen chemicals known to be weak causes of cancer that have been proposed for new or additional uses on food.