Does new cancer report overstate environmental risks?

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Cancer researchers are expressing concern over a new report highlighting the dangers of environmental toxins, suggesting that the findings overstate the risks of daily exposure to household and environmental chemicals in comparison to known risks such as smoking and obesity.

The more than 200-page report from the President’s Cancer Panel that came out last week suggests that daily exposure to carcinogens and environmental toxins is having a significant impact on cancer risk. In a letter to President Obama that prefaces the report, panel members Dr. LaSalle D. Leffall, Jr. and Margaret L. Kripke wrote that they were “particularly concerned to find that the true burden of environmentally induced cancer has been grossly underestimated.” The panel recommended that government agencies take a more proactive approach in regulating chemicals — switching from a reactionary approach to a precautionary one and placing the onus for proving product safety on manufacturers — and advised individuals to, well, be wary of everything from fertilizer to cell phone radiation. The report urged parents to “choose foods, house and garden products, play spaces, toys, medicines and medical tests that will minimize children’s exposure to toxics.”

Yet instead of rallying cancer researchers and inspiring public clamor to improve regulation, the report has left many feeling overwhelmed and confused — and elicited little response from the White House that it was meant to inform. What’s more, while cancer researchers are happy to ring some of the same alarm bells set off by the report — insufficient testing of widely used chemicals, risk of radiation exposure in medical imaging tests, etc. — the overall emphasis on environmental risk factors for cancer over better known risks such as smoking, alcohol and sexually transmitted diseases has been characterized as “unbalanced.” Dr. Michael J. Thun, vice president emeritus of Epidemiology and Surveillance Research at the American Cancer Society wrote in a statement on the organization’s web site:

“Elements of this report are entirely consistent with the recently published “American Cancer Society Perspective on Environmental Factors and Cancer,” which like the current report, identifies several areas that are of particular concern.

Issues highlighted in both reports include the accumulation of certain synthetic chemicals in humans and in the food chain; the large number of industrial chemicals that have not been adequately tested; the potentially greater susceptibility of children; the possibility that some chemicals or combinations of chemicals may have effects at low doses; and the potential risks from widely used medical imaging procedures that involve ionizing radiation.

Unfortunately, the perspective of the report is unbalanced by its implication that pollution is the major cause of cancer, and by its dismissal of cancer prevention efforts aimed at the major known causes of cancer (tobacco, obesity, alcohol, infections, hormones, sunlight) as “focused narrowly.”

The report is most provocative when it restates hypotheses as if they were established facts. For example, its conclusion that “the true burden of environmentally (i.e. pollution) induced cancer has been grossly underestimated” does not represent scientific consensus. Rather, it reflects one side of a scientific debate that has continued for almost 30 years.

There is no doubt that environmental pollution is critically important to the health of humans and the planet. However, it would be unfortunate if the effect of this report were to trivialize the importance of other modifiable risk factors that, at present, offer the greatest opportunity in preventing cancer.”

Speaking with Reuters, Dr. Graham Colditz of the Washington University School of Medicine in St. Louis said that the report’s over-emphasis on environmental toxins could actually cause more harm than good when it comes to the fight against cancer:

“Maybe up to 4 percent of cancer in the western world is caused by contaminants and pollution and yet we are chasing new, unknown causes rather that focusing on acting on what we know… Things like this report are making it harder to move the nation to a healthier lifestyle.”

Yet those on both sides of the ongoing scientific debate agree that evidence is lacking when it comes to a clear understanding of the impact of environmental toxins. While experts such as Colditz recommend focusing cancer strategies on known risks while further evidence is gathered, the panel stresses the importance of precautionary measures — acting on what evidence we do have until more proof is available. (For example, though the report concedes that there is currently no solid science suggesting the danger of cell phone radiation, the panel still encourages people to reduce exposure to “electromagnetic energy by wearing a headset when using a cell phone, texting instead of calling, and keeping calls brief.”)

Most public health guidance is governed by conservative interpretations of the best available science — for example, in spite of many small-scale studies analyzing the effect of things like exercise and diet on dementia risk, the National Institutes of Health recently concluded that there was not yet enough rigorous research to suggest any effective methods for preventing Alzheimer’s. While in the recent cancer report it’s evident that emphatic evidence is lacking for many potential risks, the report does illustrate the authors’ efforts to spur a sea change in public health policy — toward erring on the side of caution by reacting to potential risks first and filling in the science later.