The President’s Cancer Panel has released a report on the causes of cancer and how we might best avoid them. Among its recommendations: Take off your shoes before entering your home.
The panel’s 200-plus-page report is a scientific travesty that claims environmental chemicals have been routinely understated as a cause of cancer. Made up of just two members — Dr. LaSalle Leffall of Howard University and Dr. Margaret Kripke, professor emeritus at the M.D. Anderson Cancer Center in Houston —the panel concluded that there is “grievous harm” being done by chemicals and there is “a growing body of evidence linking environmental exposures [to chemicals] to cancer.”
If Dr. Leffall and Dr. Kripke had simply consulted a standard textbook on cancer epidemiology, they would have learned that lifestyle factors such as smoking, obesity, excessive alcohol consumption, and overexposure to sunlight are the underlying preventable causes of human cancer — not “chemicals” in air, water, and food.
The panel’s report, which was roundly criticized by the American Cancer Society and other experts on cancer causation, was constructed on a number of false premises:
1. It assumed that “chemicals” are dangerous by definition and our exposure to them should be limited. Well, that would indeed be a problem, since all things, natural and synthetic, are comprised of “chemicals.” When you have a cold, refreshing glass of water, you are drinking dihydrogen monoxide.
2. It assumes that our goal in cancer prevention should be to eliminate all exposure to “toxic” and “carcinogenic” agents. Sorry, that is impossible. Safe, natural foods come replete with toxins (such as the traces of naturally occurring arsenic in every potato) and “carcinogens,” defined as chemicals that cause cancer at high dose in laboratory animals (like the safrole in black pepper or the eatechol in a cup of coffee).
3. The panel appears to be oblivious to the concept of “dose” — as expressed in the classic toxicological premise “only the dose makes the poison.” Exposure to chemicals like vinyl chloride at high levels for long periods of time has indeed, decades ago, caused cancer in the workplace. Such true human carcinogens are always detected via careful collection of epidemiological data. But that level of occupational exposure has no relationship to environmental exposure to trace levels of chemicals.
4. The panel relies upon and endorses the so-called “precautionary principle,” which demands that every chemical be proven safe before it is used. How can you prove anything to be safe? You can’t. It’s like trying to prove a negative.
For example, the panel’s report repeatedly targets the chemical BPA as posing numerous health risks, including cancer. BPA is a ubiquitous industrial chemical — essential in the manufacture of many hard plastic products — and used in the lining of cans to prevent the development of foodborne illnesses, such as botulism. BPA has been used for over 50 years and subjected to thousands of safety evaluations. Expert panels from around the world (including our own Food and Drug Administration and Environmental Protection Agency) have concluded that BPA is safe as used. Yet the panel still raises anxieties about adverse health effects from this chemical. In other words, despite all the studies, under the panel’s “precautionary principle,” BPA still does not make the cut to be labeled “safe.” Under that standard, what chemical would ever get the government’s seal of approval?
The President’s Cancer Panel is an assault on the science of cancer epidemiology. Its findings — such as avoiding environmental cancer-causing agents by taking off your shoes and leaving the “carcinogens” you picked up on the way home at the doorstep — are ludicrous and, by distracting Americans from the proven cancer risk factors, are more likely to increase than decrease our nation’s cancer burden. This prestigious-sounding panel (which New York Times columnist Nicholas Kristof dubbed “the Mount Everest of the medical mainstream” — it isn’t) urges us to eat organic foods, filter our water, and microwave only using ceramic or glass, rather than plastic — instead of confronting us with the truth: At least 35 percent of cancer deaths this year can be causally linked to cigarette smoking, and another significant percentage can be traced to other lifestyle factors such as obesity. The exact contribution of environmental chemicals to our nation’s cancer toll has not been calculated — but today the best estimate of that contribution is close to zero.