This article first appeared on TCSDaily.com.
For years, self-appointed "environmental advocates" have generated press releases claiming that "chemicals" in our air, water, food, and consumer products such as cosmetics pose a risk of cancer. Nearly twenty years ago, the Natural Resources Defense Council caused a national panic by asserting that the agricultural chemical Alar posed a cancer risk to children (a claim that was later determined to be false). Advocates on Long Island have long claimed -- with a paucity of evidence -- that the elevated breast cancer rate in that area is the result of exposure to environmental chemicals like PCBs and DDT. These assertions can be dismissed as pure scare tactics, as they are not based on scientific data which have survived the rigor of the peer review process and been published in a professional medical journal.
But data and conclusions reported in peer review journals are sound and trustworthy, right? Wrong.
Apparently, we can no longer assume that peer review journals are free of "junk science." The peer-reviewed journal Cancer, a publication of the American Cancer Society (ACS), just published a special online supplement that clearly meets the definition of "junk" in every way.
This journal, which boasts a long and distinguished list of editorial advisors, featured an article by Dr. Julia Brody, the executive director of the Silent Spring Institute and researchers from the Roswell Park Cancer Institute. The journal supplement section was funded by the foundation Susan G. Komen for the Cure. Brody is the principal investigator of the Cape Cod Breast Cancer and Environment Study -- a study of exposures to "mammary carcinogens" from air and water pollutants , pesticides, detergents, plastics, and cosmetics.
Why is this study "junk"? Let me count the ways:
First, the conclusions drawn by the authors, namely that environmental pollutants cause breast cancer, are not based on human studies but instead on high-dose animal studies. The authors identify a series of synthetic chemicals that cause breast tumors in rodents and then leap to the assumption that these chemicals also cause breast cancer in women.
There is now a nearly-universal rejection by scientists of the use of laboratory rodent data to predict human cancer risks. Thus, it is astounding that this lengthy paper is predicated on the assumption that rodents are just "little women." Indeed, in a companion article in the same Cancer supplement -- this one written exclusively by staff members of the Silent Spring Institute -- the authors recklessly elevate the role of rodent tests by asserting that "identifying chemical carcinogens in animal studies is currently the primary means of anticipating cancer effects in humans." If indeed that statement were true, we would be classifying a whole host of natural foods as "cancer risks" because they naturally contain chemicals that cause cancer in rodents -- including mushrooms (hydrazines), table pepper (safrole), and bread (ethyl carbamate)
Second, the authors brazenly conclude that, while they cannot state with confidence how many breast cancer cases annually are due to exposure to trace levels of "chemicals" (including pesticides, ingredients in cosmetics and other "environmental pollutants"), they feel the evidence (what evidence?) is strong enough to warrant "strategies" to reduce exposures in an effort to reduce breast cancer risk.
Further, it is clear from the affiliation of the senior author that this "study" was in no way neutrally conducted. In its own description, the Silent Spring Institute claims to be "a non-profit scientific research organization dedicated to identifying the links between the environment and women's health, especially breast cancer." The study was commissioned by the Susan G. Komen foundation's "environmental factors and breast cancer" project. Thus from the get-go the assumption is that breast cancer is causally linked to "environmental" factors -- specifically chemicals in the environment. This article is not science -- it is environmental advocacy.
Apparently, the peer reviewers of this paper were unfazed by the authors' conclusion that trace chemicals cause breast cancer, despite the fact that this idea is completely at variance with our understanding of the epidemiology of breast cancer. No serious cancer causation expert believes exposure to trace levels of environmental chemicals contributes to the toll of breast cancer.
In the latest edition of the "bible" of cancer epidemiology (Cancer Epidemiology and Prevention, edited by Schottenfeld and Fraumeni), the authors reviewed the causation of breast cancer by assessing the role of "environmental factors" in the causation of breast cancer -- meaning factors other than heredity, age, gender, etc. They considered the influences of reproductive factors (for example, having a first child at an early age may offer protection), use of hormones, weight, and nutritional factors (obesity after middle age is a risk factor for breast cancer). They then evaluated the claim that "other environmental factors" contribute to breast cancer risk -- including exposure to trace levels of pesticides and industrial chemicals. They concluded that evidence from large pooled human studies found no association between exposure to trace chemicals like PCBs and DDT and breast cancer risk: "Overall, recent studies have not found evidence of increased risk of breast cancer, and [pollutants] appear unlikely to be major breast cancer risk factors."
A quick review of the Pub Med articles bank reveals numerous epidemiological articles looking for a possible link between breast cancer risk and PCBs, DDT, and other chemicals -- and they end with the conclusion that "the combined evidence does not support an association with breast cancer risk." ACS's own Detailed Guide: Breast Cancer What Are the Risk Factors for Breast Cancer? says "research does not show a clear link between breast cancer risk and exposure to environmental pollutants."
Yet the Cancer article made little mention of the fact that human epidemiological studies contradict the conclusions that are based on lab-rat "evidence."
Media, interested in sensationalizing environmental health risks, used this story uncritically. The LA Times headline was week was "Common Chemicals Linked to Breast Cancer." Readers were led to believe that "overall exposure to mammary gland carcinogens is widespread" -- when there is no legitimate science to back up such a frightening claim. And of course, such reporting predictably sparked outrage: an editorial in the San Francisco Chronicle blasted "cancerous chemicals" and went even further than the study authors did, asserting that these chemicals may be a more important factor in determining breast cancer risk than genetics. The editorial called for more laws, more regulations to protect women from "carcinogens."
The American Cancer Society has done the cause of breast cancer prevention a disservice by publishing this article. ACS has tarnished the much-touted image of the peer review process as something superior to the "science by press release" approach. The article diverted attention from scientifically-based ways of reducing breast cancer risks (including using FDA-approved medications as a means of chemo-prevention -- an approach that shows great promise).
Recent news documents that fewer women are getting mammograms over the past several years -- a decline that reversed the salutary trend of the past twenty years. This is important, and women need to be reminded to get their mammograms. Yet, instead of focusing women's attention on the critical importance of early detection -- and the good news about treatment and very low rates of recurrence -- the ACS has supported unfounded fears of inescapable, invisible, chemical agents causing cancer in helpless women. Both the ACS and the Susan G. Komen organization should be ashamed of this report.
