WASHINGTON -- America's War on "Carcinogens": Reassessing the Use of Animal Tests to Predict Human Cancer Risk avoids many of the traps associated with academic works, even though a panel of Ph.D.s and M.D.s wrote it for the American Council on Science and Health. The book takes care to define jargon like bioassay (a cancer test using a near-lethal dose of a substance). And with a text of barely 140 pages, the book is also concise. The intelligent layman will find it readable, which is good since America's War on "Carcinogens" has quite a story to tell.
This book challenges the notion that cancer is a modern disease caused by increased exposure to synthetic chemicals. While it is true that cancer accounted for less than 4% of all U.S. deaths in 1900 but 23% in 2000, the authors point out that the major cause is the increase in cigarette smoking and the longer life expectancy of a population no longer susceptible to past epidemics. But try telling that to the activists who have targeted synthetic chemicals to a host of misconceived rules and regulations.
One major problem with current regulatory policy is its reliance on animal testing. Most cancer testing today is usually performed on rats and mice. But humans are not rodents. As the book notes: "Findings of carcinogenicity in animal tests are not strongly predictive of human carcinogenicity. Only a limited number of chemicals initially found to cause cancer in animals have been subsequently found to be human carcinogens." Another problem with rats and mice is that the breeds "most commonly used…have high spontaneous rates of certain types of tumors; this limits their predictive value." Finally, animal tests typically use the "maximum tolerated dose" (MTD). The MTD is the highest amount of a substance that can be tested on rats and mice without killing them. But humans are almost never exposed to such high levels. For example, a human would have to drink 7,500 cans daily of a soda containing red dye #2 to achieve the test levels that caused the dye to be banned as potentially carcinogenic.
Unfortunately, most cancer agencies (e.g., the International Agency for Research on Cancer, the National Toxicology Program, and the Environmental Protection Agency) rely on animal testing to determine whether a substance is likely to cause cancer in humans. The National Cancer Institute (NCI), the federal government's principal cancer research agency, relies on a mix of animal and human data. Still, the book faults NCI for not taking "a lead role in informing the public about whether exposure to trace levels of synthetic chemicals in the environment contributes to the human cancer toll."
Once a substance is deemed a carcinogen, it is subject to the "Delaney clause" of the 1958 Federal Food, Drug and Cosmetic Act. It states that
No additive shall be deemed to be safe if it is found to induce cancer when ingested by man or laboratory animals or if it is found, after tests which are appropriate for the evaluation of the safety of food additives, to induce in man or animals.
However, the Delaney clause is also a grandfather clause because it only applies to new additives and substances. All substances recognized as safe before adoption of the 1958 law are allowed. That has produced a classic unintended and perverse effect. The authors observe:
One result of the Delaney clause has been to preclude the replacement of [old] substances or those approved before 1958 with newer, possibly safer or more effective alternatives, because the law forbids any risk whatsoever for substances given new regulatory approvals but holds the older substances to a looser standard. Thus, one unintended result of the Delaney clause had been to discourage innovation, even if such innovation could have resulted in food products with enhanced quality or safety.
The unintended effect of the Delaney clause has been deadly. For instance, it is now estimated that at least 30 million people worldwide have died from malaria, a disease once prevented by DDT. But DDT was banned after researchers discovered that it caused cancer in mice. Ethylene Dibromide (EDB) is a pesticide once used on fruit, and apple growers used Alar to slow growth in certain types of apples and prevent rotting. The cancer risk for humans of these two chemicals is virtually zero. However, once public hysteria reached fever pitch their use was discontinued. Farmers now resort to less effective alternatives, which makes their crop smaller and their fruit less affordable for consumers. Since studies routinely show that high fruit intake is linked to a reduction in some types of cancer the result is that we actually may be less safe than before use of these pesticides was ended.
Unfortunately, American regulatory policies tend to reinforce the activist-led cancer scare campaigns based on shaky science. We would be far better off with a public health system that conveys sensible information on real cancer risks like cigarette smoking and over-exposure to sunlight. What can policymakers do to inform themselves about misleading scare campaigns? A good place to start would be to read America's War on Carcinogens.
(Note: the Cato Institute will be holding a book forum on America's War on Carcinogens today. For more information, go here.)