Misconceptions About Environmental Pollution, Pesticides and the Causes of Cancer

Policy Reports | Energy and Natural Resources

No. 214
Sunday, March 01, 1998
by Bruce N. Ames and Lois Swirsky Gold

Executive Summary

  1. The major causes of cancer are:
    a) Smoking: About a third of U.S. cancer (90 percent of lung cancer);
    b) Dietary imbalances, e.g., lack of dietary fruits and vegetables: The quarter of the population eating the least fruits and vegetables has double the cancer rate for most types of cancer compared to the quarter eating the most;
    c) Chronic infections: mostly in developing countries; and
    d) Hormonal factors: primarily influenced by life style.
  2. There is no epidemic of cancer, except for lung cancer due to smoking. Cancer mortality rates have declined 16 percent since 1950 (excluding lung cancer).
  3. Regulatory policy that focuses on traces of synthetic chemicals is based on misconceptions about animal cancer tests. Recent research indicates that:
    a) Rodent carcinogens are not rare. Half of all chemicals tested in standard high dose animal cancer tests, whether occurring naturally or produced synthetically, are "carcinogens";
    b) There are high-dose effects in rodent cancer tests that are not relevant to low-dose human exposures and that contribute to the high proportion of chemicals that test positive;
    c) The focus of regulatory policy is on synthetic chemicals, although 99.9 percent of the chemicals humans ingest are natural. More than 1,000 chemicals have been described in coffee: 28 have been tested and 19 are rodent carcinogens. Plants in the human diet contain thousands of natural pesticides that protect them from insects and other predators: 63 have been tested and 35 are rodent carcinogens.
  4. There is no convincing evidence that synthetic chemical pollutants are important for human cancer. Regulations that try to eliminate minuscule levels of synthetic chemicals are enormously expensive: The Environmental Protection Agency has estimated that environmental regulations cost society $140 billion per year. Others have estimated that the median toxic control program costs 146 times more per life year saved than the median medical intervention. Attempting to reduce tiny hypothetical risks also has costs; for example, if reducing synthetic pesticides makes fruits and vegetables more expensive, thereby decreasing consumption, then cancer will be increased, particularly for the poor.
  5. Prevention of cancer will come from knowledge obtained from biomedical research, education of the public and lifestyle changes by individuals. A re-examination of priorities in cancer prevention, both public and private, seems called for.

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