Pesticide Industry Propaganda: The Real Story

The Real Story Behind the Myths

May 1, 1995

Pesticide Industry Propaganda: The Real Story: Myth 5: Natural carcinogens in food are more dangerous than pesticide residues

Myth #5: Natural carcinogens in food are more dangerous than pesticide residues, so pesticides are not worth regulating.

This is an extremist view, not supported by replicated peer-reviewed studies and not accepted by the scientific or regulatory community. The principal proponent of this view is Dr. Bruce Ames, a prominent Berkeley biochemist. Many scientists have detailed the flaws in the Ames theory.

First, Ames brands many natural substances as carcinogens on the basis of flimsy or equivocal evidence, such as causing tumors only from a high dose, precisely the argument he rejects when applied to man-made carcinogens (NRC 1993a, Perrera et al. 1988).

Second, some of the natural carcinogens cited by Ames are not carcinogens at all. One of his top three alleged natural carcinogens, d-limonene, is not considered carcinogenic by any credible regulatory or international scientific agency (Huff 1993, EPA 1994b).

Third, Ames looks at only a handful of pesticides in the food supply, dramatically understating the total load of cancer-causing pesticides in food and water. Dr. Frederica Perrera and colleagues constructed a more representative, but still incomplete, list of man-made carcinogens and found exposure to these compounds to be about equal to that of natural carcinogens cited by Ames. (Perrera et al. 1988).

Fourth, Ames incorrectly inflates exposure to natural carcinogens. For example, he assumes that everyone in the United States drinks a cup of comfrey tea each day when illustrating the danger of natural carcinogens, but uses far smaller average food consumption estimates for the entire U.S. population when calculating the dangers of DDT in the diet.

Fifth, Ames does not consider that children may get far higher doses of synthetic or natural carcinogens than adults, based on their unique eating habits.

Sixth, Ames ignores the fact that the risks from some man-made carcinogens are low precisely because these carcinogens have been regulated. The issue of natural vs. man-made carcinogens is one of ethics and common sense. Just because natural sources of cancer risk exist, it doesn't follow that we should add more synthetic carcinogens to the food, air, and water supply. Americans want avoidable cancer risks reduced, whether they are from naturally occurring aflatoxins or man-made pesticides.