Carson's Legacy of Junk Science

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This piece appeared in the Orange County Register.

Rachel Carson, who would have turned 100 today, wrote Silent Spring, the book published in 1962 that started the modern wave of anti-chemical environmental paranoia. Now, even peer-reviewed scientific journals are absent-mindedly repeating her brand of scare-claims.

Peer review -- subjecting a scientist's work to the scrutiny of colleagues before it is published -- is considered essential in the quest to separate good science from just plain junk. We have great faith in the data and conclusions we read in peer reviewed journals and we see a sharp difference between peer-reviewed conclusions and the daily "science by press release" that floods the desks of journalists.

But what happens if peer review fails and a peer-review journal publishes junk?

On May 14, the peer-review journal Cancer, a publication of the American Cancer Society with a distinguished editorial board, posted a special online supplement that concluded that breast cancer is caused by trace chemicals in the environment -- including pesticides, chemicals in cosmetics, and contaminants such as PCBs and DDT (the latter being the pesticide that was globally banned in the aftermath of "Silent Spring," creating conditions for mosquitoes to flourish and for a resurgence of human malaria infections and millions of deaths since the 1970s).

The lead author of the main article is the executive director of the Silent Spring Institute, which describes itself as "a nonprofit scientific research organization dedicated to identifying the links between the environment and breast cancer."

The study was commissioned by the Susan G. Komen for the Cure foundation's "environmental factors and breast cancer project."

Clearly, right from the get-go the assumption was that breast cancer is causally linked to "environmental" factors -- specifically, environmental chemicals. That observation alone should have tipped peer reviewers off to the fact that the work in question may not be science but rather environmental advocacy.

Why is this study "junk"? Let me count the ways:

First, its conclusion that chemicals cause breast cancer is based on animal cancer tests. Since we know that animal tests on rats cannot even predict cancer risks in mice, how could the authors make the assumption that rodents are little women? Second, the authors conclude that while they cannot state with confidence how many breast cancers are caused by "chemicals," they feel the evidence (what evidence?) is strong enough to warrant "strategies" to reduce exposures and thus reduce the burden of breast cancer.

Apparently, the peer reviewers of this paper were unfazed by the authors' conclusions that trace chemicals cause breast cancer, despite the fact that this is at total variance with current understanding of the epidemiology of breast cancer. The classic textbooks in this field review the influence of reproductive factors in breast cancer risk (for example, having a child at an early age may reduce a woman's risk, while not having children may somewhat increase it), use of hormones, weight (obesity after middle age is a risk factor), family history, etc. But these authoritative sources dismiss "trace chemicals" as a cause or risk factor. Even the American Cancer Society's Web site has long noted that "research does not show a clear [link] between breast cancer risk and exposure to environmental pollutants."

Many journalists took notice of the new study uncritically. The headline on a story in the Los Angeles Times proclaimed "Common Chemicals Linked to Breast Cancer" and quoted from the study paper that "overall exposure to mammary gland carcinogens is widespread." An editorial in the San Francisco Chronicle blasted "cancerous chemicals" and went even further than did the "study" -- asserting that chemicals may be a more important risk factor than even genetic predisposition.

We do not know where the peer-review process went wrong here, but it is clear that the American Cancer Society has done the cause of breast cancer prevention -- and the institution of peer review -- a great disservice by issuing this publication. Instead of reminding women to have regular mammograms and spreading the good news about new, highly effective treatments for breast cancer (and astonishingly low recurrence rates for early stage cancers), the ACS has supported unfounded fears about allegedly inescapable, invisible, hostile chemical agents leaving vulnerable women at risk.