Thursday, October 11, 2007
By Steven Milloy
Ever since the World Health Organization reversed the environmentalist-promoted ban on DDT in 2006,
eco-activists have scrambled to devise new ways to malign the life-saving insecticide in order to salvage
their badly marred reputation.
Their latest effort involves touting a new study
supposedly linking DDT exposure in adolescent girls with increased breast cancer risk in later life. The study
was authored by researchers from the Mount Sinai School of Medicine — an institution infamous for alarmist
research on asbestosand
9-11 rescue workers — and was published in Environmental Health Perspectives, a journal that seems to
operate as a refuge for alarmist research.
The study first came to my attention via a letter by John Peterson Myers published in The Wall Street Journal
(Aug. 25) entitled “Stop Pushing DDT.” Aficionados of health scares will recall that Myers
was a co-author of the 1996 book “Our Stolen Future,” which fomented fears about chemicals in the
environment causing every disease from cancer to attention deficit disorder.
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A pro-DDT editorial by the Journal (Aug. 16) spotlighted new research countering the environmentalist
claim that DDT is ineffective because mosquitoes can build resistance to the chemical’s toxic properties.
In taking exception to the Journal’s advocacy of DDT to combat the malaria — a disease that sickens 500
million per year, killing 1 million of them — Myers cited the Mount Sinai study and its claim that “women
more exposed to DDT prior to puberty were five times more likely to develop breast cancer than those with
lower exposure.” Myers pointed out that the authors concluded that “the public-health significance of DDT
exposure is potentially large.”
I responded to Myers with a letter published in the Journal (Aug. 31) likening the study to statistical
The study was small (including only 133 women with breast cancer), completely omitted data on key risk factors
for breast cancer (such as genetics and family history) and only partially considered other potential risk
factors (such as pregnancy and breast-feeding history). All of which amply explains the study’s internal
contradictions and statistical flakiness.
The vast majority of the statistical correlations reported in the study were either zero or negative —
meaning no relationship between DDT and breast cancer. Accepting the negative ones at face value, as Myers did
the positive, would support the equally unlikely implication that DDT might actually prevent breast cancer.
Moreover, the positive correlations were highly suspect.
The one cited by Myers — the five-fold increase in breast cancer risk — sports a wide margin of error,
four times the size of the claimed correlation.
The Mount Sinai researchers responded with their own letter in the Journal (Sept. 22). Acknowledging that
their study was small, their primary line of defense was that it was published in a reputable journal and was
peer-reviewed by experts in the subject area, hardly a defense on the study’s merits, particularly given the
particular journal in question.
While they acknowledged failing to consider genetic risk and family history of breast cancer in the study,
they tried to excuse this lapse by glibly dismissing the two universally recognized breast cancer risk factors
as being “unlikely to change the result.”
The final letter in this series (from Randall Dodd of Mill Creek, Wash., on Sept. 29) observed that the
largest study on this subject found no link between DDT and breast cancer and that skepticism should be on
“full alert status” whenever a small study contradicts all previous science done previously.
“A new study has found a significant link between women’s exposure to DDT as young girls and the
development of breast cancer in later life,” Weiss begins. From there, he largely regurgitates the
researchers’ results and views in uncritical fashion, including the denigration of the numerous previously
published studies that found no link between DDT and breast cancer.
Although Weiss acknowledged to me that he had seen the exchange of letters in The Wall Street Journal, he
inexplicably chose not to report that the study results had been so challenged.
Weiss closes his article with comments from Cornell University’s Suzanne Snedeker, a nutritionist by
training who said that she had serious concerns about a DDT comeback in developing countries and would rather
see funding for other approaches to malaria control.
Assuming purely for the sake of argument that DDT does increase the risk of breast cancer, do Snedeker’s
concerns even make any sense?
Zimbabwe, for example, has about 2,000 cases of breast cancer per year, affecting about 0.016 percent of the
population. In contrast, about 1.5 million cases of malaria occur there annually, affecting more than 12
percent of the population.
Avoiding the use of DDT to control malaria in Zimbabwe and other similarly afflicted areas because of concerns
of breast cancer is clearly absurd — only made more so by the speciousness of the claim that DDT increases
breast cancer risk.
As Randall Dodd concluded in his Wall Street Journal letter, “… in the context of the millions of people,
principally children, who die from malaria every year, even if one suspends disbelief and grants the [Mount
Sinai researchers] their findings, an elevated potential risk of the maladies they mention is outweighed
exponentially by the certainty of millions of deaths, most of them avoidable, from malaria.”
Mr. Dodd’s point is so obvious and true that it ought to raise questions about the ulterior motives of those
who dispute it.
Steven Milloy publishesJunkScience.comandDemandDebate.com.
He is a junk science expert, and advocate of free enterprise and an adjunct scholar at the Competitive
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