Study: Synthetic Chemicals Not Major Cause of Cancer

Published May 1, 1998

Human exposure to carcinogenic pesticides is minuscule compared to the “background” exposure to carcinogens produced by nature, according to a new report from two of the nation’s leading cancer experts.

According to Bruce Ames and Lois Swirsky Gold, authors of a March 1998 study released by the Dallas-based National Center for Policy Analysis (NCPA), some 99.9 percent of all pesticides that humans eat are naturally produced by plants to protect themselves against fungi, insects, and animal predators. Americans eat about 10,000 times more natural pesticides per person, per day (measured by weight) than they consume of synthetic pesticide residues.

Ames, a professor at the University of California at Berkeley, developed the “Ames test,” used by scientists worldwide to determine whether a chemical causes mutations and is therefore likely to cause cancer in laboratory tests. Gold is director of the Carcinogenic Potency Project at the National Institute of Environmental Health Sciences Center at Berkeley.

Naturally occurring rodent carcinogens have been identified in an ordinary list of food and drinks, including lettuce and tomatoes; potatoes and corn; broccoli, cabbage, and peas; hamburgers; orange juice and chocolate milk; black pepper; and wine and beer. Carcinogens have even been found in 49 percent of the prescription drugs that have been tested.

Although Ames developed the test for potential carcinogens, he is concerned that animal cancer test results are misleading, with cancer scare stories causing people to avoid items ranging from apples to soft drinks. In fact, Ames isn’t even sure that it’s the chemical itself that actually causes cancer in laboratory experiments. “Evidence suggests that it’s the high doses themselves, not the chemicals tested, that cause cancer,” he says.

Our biggest risk of cancer comes not from pesticides and food additives, but from ordinary lifestyle choices. The study points out that:

  • Smoking contributes to 35 percent of U.S. cancer cases.
  • Unbalanced diets account for about one-third of all U.S. cancer cases.
  • Reproductive hormones contribute to as much as 20 percent of all cancer, and lack of exercise, obesity, and alcohol intake influence hormone levels and increase risk.
  • Chronic infections cause about 9 percent of all cancer cases in the U.S.
  • Cancer also is due in part to natural aging processes.

Not only are fears about synthetic pesticides rarely justified, but reducing their use may do more harm than good. Fruits and vegetables raised without synthetic pesticides are more expensive. If higher prices cause people to buy less produce, human health will suffer.

Epidemiologic evidence indicates that the 25 percent of the population with the lowest dietary intake of fruits and vegetables has roughly twice the cancer rate as does the 25 percent with the highest consumption level. Abandoning the use of synthetic pesticides in favor of organically grown crops, therefore, would likely cause cancer rates to rise.

“Unbalanced diets–diets that are too low in fruits and vegetables, for example–cause about a third of all cancer deaths,” Gold said. “That’s about the same number that die of cancer caused by smoking.”

The NCPA study also shows that regulating low-level exposure to carcinogens does little to advance public health. EPA estimates that environmental regulations cost society about $140 billion a year, more than $1,000 for every household in America. Much of this regulation is designed to protect people from low-level exposure to synthetic chemicals that cause cancer in rodents.

That money is not well spent, Ames and Gold argue. The U.S. could prevent 60,000 deaths per year by directing the same amount of money to more cost-effective programs.