Book Debunks Synthetic Chemical, Pesticide Fears: Part 1 of 3

Published June 1, 2003

Cancer scares raised by the Environmental Protection Agency and environmental activist groups frequently focus on dangers posed by man-made chemicals. A new book from the Vancouver-based Fraser Institute says that focus is wrong, because synthetic chemicals have little to do with human cancer.

“Few epidemiological studies find an association between the risk of cancer and low levels of industrial pollutants or pesticide residues,” write the authors of Misconceptions About the Causes of Cancer, released in February. “[A]ssociations are usually weak, the results are often conflicting, and the studies usually do not address individual pesticides.”

The book is authored by four leading scientists and cancer researchers: Lois Swirsky Gold, senior scientist and director of the Carcinogenic Potency Project at the University of California, Berkeley; Thomas H. Slone and Neela B. Manley, scientists with the Carcinogenic Potency Project; and Bruce N. Ames, professor of biochemistry and molecular biology and a senior scientist at the Children’s Hospital Oakland Research Institute.

Misconceptions About the Causes of Cancer is the third publication in the Fraser Institute’s Risk Controversy Series. The series aims at promoting good public policy, based on sound science and sound economics, by providing readers with information from scientists about the complex science involved in many of today’s important policy debates. Other publications in the series include Global Warming: A Guide to the Science and Biotechnology & Food for Canadians.

Following are excerpts from the book.

Synthetic Chemicals

“Neither epidemiology nor toxicology supports the idea that exposures to synthetic industrial chemicals at the levels at which they are generally found in the environment are important causes of human cancer. Instead, other environmental factors have been identified in epidemiological studies that are likely to have a major effect on lowering cancer rates: reduction of smoking, improving diet (e.g. increased consumption of fruits and vegetables), hormonal factors (some of which are diet-related), and control of infections.” (page 7)

“Reduction in the use of pesticides will not effectively prevent diet-related cancer. Diets high in fruits and vegetables, which are the source of most human exposures to pesticides residues, are associated with reduced risk of many types of cancer. Less use of synthetic pesticides would increase costs of fruits and vegetables and, thus, likely reduce consumption, especially among people with low incomes, who spend a higher percentage of their income on food.” (page 15)

“Contrary to common perception, 99.9% of the chemicals humans ingest are natural. The amounts of synthetic pesticide residues in plant foods, for example, are extremely low compared to the amounts of natural “pesticides” produced by plants themselves. Of all dietary pesticides that humans eat, 99.99% are natural: these are chemicals produced by plants to defend themselves against fungi, insects, and other animal predators. Each plant produces a different array of such chemicals.” (page 23)

“On average, the Western diet includes roughly 5,000 to 10,000 different natural pesticides and their break-down products. Americans eat about 1,500 mg of natural pesticides per person per day, which is about 10,000 times more than they consume of synthetic pesticide residues. Even though only a small proportion of natural pesticides has been tested for carcinogenicity, half of those tested have been found to be carcinogenic in rodents.” (page 23)

“In a single cup of coffee, the natural chemicals that are rodent carcinogens are about equal in weight to an entire year’s worth of synthetic pesticide residues that are rodent carcinogens, even though only 3% of the natural chemicals in roasted coffee have been adequately tested for carcinogenicity. This does not mean that coffee or natural pesticides are a cancer risk for humans, but rather that assumptions about high-dose animal cancer tests for assessing human risk at low doses need reexamination. No diet can be free of natural chemicals that are rodent carcinogens.” (page 24)

“Humans have many natural defenses that buffer against normal exposures to toxins; these usually are general rather than tailored to each specific chemical. Thus, the defenses work against both natural and synthetic chemicals.” (page 27)

“Since no plot of land is free from attack by insects, plants need chemical defenses–either natural or synthetic–in order to survive. Thus, there is a trade-off between naturally occurring and synthetic pesticides. One consequence of disproportionate concern about residues from synthetic pesticides is that some plant breeders develop plants that are more insect-resistant because they are higher in natural toxins.” (page 29)

For more information …

The full text of Misconceptions About the Causes of Cancer is available in Adobe Acrobat’s PDF format on the Fraser Institute’s Web site at The book can also be ordered from the Fraser Institute for $19.95 (CAN) plus $10.00 shipping and handling. Call 604/688-0221 or email your order to [email protected].