The risks of cancer from pesticides and other synthetic chemicals in the American diet are "quite insignificant" compared with the natural toxins that make up more than 99 percent of the cancer-causing substances we ingest, researchers say.
"Our results indicate that many ordinary foods would not pass the regulatory criteria used for synthetic chemicals," said scientists from the University of California at Berkeley, in an article published in today's issue of the journal Science.
The scientists said people should not worry unduly about developing cancer from natural toxins, but they did say that regulatory agencies concerned with protecting Americans from cancer risks should place more emphasis on studying carcinogens that occur naturally.
Present policy focuses on synthetic pesticides in food and water, which people consume only in minute amounts, wrote the authors, headed by Lois Swirsky Gold of the Lawrence Berkeley Laboratory and Brune N. Ames of UC Berkeley.
"Our priorities aren't right, if our goal is to prevent human cancer," Ms. Gold said yesterday.
Essentially the same message was contained in a preliminary report that Mr. Ames and Ms. Gold published in 1987.
Ms. Gold said that since the original study, the authors of the Science report have compiled a database that includes 4,200 experiments in which 1,200 chemicals were tested for their cancer-causing activity. They also compiled data on the amounts of these chemicals to which Americans are exposed in their diet. The natural substances, including toxins found in wine, beer, lettuce and other vegetables, orange juice, coffee and bacon, ranked near the top of the list; pesticides ranked near the bottom.
But Ms. Gold cautioned that this does not mean the public should worry too much about developing cancer from food toxins. The report, instead, is intended to correct the widespread notion that chemicals like pesticides, because they are synthetic, must be more dangerous than those that occur in nature.
By far the major preventable risk factors for cancer are use of tobacco, eating too much or too little of certain foods, hormonal changes, and chronic infections, the report said.
An official of the Environmental Protection Agency said yesterday that while many scientists agree on the need for more testing of natural food components, "there's no legislative mandate to do it."
The EPA is specifically charged with regulating pesticides in food, but not natural substances, said Dr. Penny Fenner-Crisp, of the EPA's Office of Pesticide Programs.
However, she said that since Mr. Ames and Ms. Gold's earlier report, "there has been some discussion about taking into greater consideration some of these [natural] chemicals for testing."