Deodorants, Antiperspirants Cause Breast Cancer

The Scare:
Since breast cancer is the second most frequent cause of cancer deaths in American women (only lung cancer kills more),(125) it is understandable that any possible factor contributing to its occurrence garners much media attention. Unfortunately, some reports of potential causal factors do not reflect solid scientific consensus, and thus are alarmist rather than informational. Such is the case of the supposed link between antiperspirants, deodorants and breast cancer.

Where Did the Scare Come From?
The website of the Environmental Working Group (EWG) is one ready source of such concerns. The EWG posted a report of their own called “Skin Deep”(126) which scored a variety of cosmetic ingredients for their putative danger to human health. The scientific validity of their scoring system is unknown, and thus it is not at all clear that it represents any realistic evaluation of health risk.

Reporting of the link between deodorants/antiperspirant products and breast cancer risk tended to be more evenhanded than the EWG report. Reporters typically cited two recent studies. One (McGrath(127)) examined the underarm shaving habits and use of antiperspirants of over 400 breast cancer victims and found a correlation between the frequency of such habits and the age at which they were diagnosed with breast cancer. More intensive use was correlated with a younger age of cancer development. The author suggested this correlation indicated a causal connection between shaving, antiperspirant use, and breast cancer. The other study (Darbre et al.) examined samples of breast cancer tissue and found preservatives (parabens) in deodorants and antiperspirants, as well as other cosmetic products.(128) The authors concluded that the presence of these chemicals provided support for the hypothesis that they might have caused the breast cancer.

The Media Coverage:
Some Internet sites (e.g., breastcanceraction.com) seem to take it as a given that the chemicals in antiperspirants and deodorants (especially aluminum and parabens) are causally linked to breast cancer. Others are somewhat more circumspect, labeling such a connection as more speculative, although still supporting the idea that chemicals in cosmetics should be seen as potentially dangerous carcinogens.(129) The news media covered the issue widely, with reports from Reuters used on MSNBC,(130) coverage on NBC in Chicago, a report in the New Scientist(131) in January, and one in the Milwaukee Journal Sentinel. To their credit, for the most part these outlets provided a fairly balanced view of the issue. They described both the recent research publication that was the impetus for the news report(132) and other reports that contradicted these findings.(133) The New Scientist report, for example, noted that this study provided “the first evidence of such a link to appear in a peer-reviewed journal, but it is far from conclusive.”

The Bottom Line:
There were flaws in both of the original studies that seriously undermined the strength of their conclusions. First, the study of the breast cancer victims had no control group: there was no way to know if women of similar ages, ethnic groups, or lifestyles who did not develop breast cancer had the same or different hygiene habits. If they were the same, that would not support a link between such habits and breast cancer. Further, an earlier epidemiologic study that had included both 813 women with and 793 women without breast cancer found no such link.(134) This is a stronger experimental design that allows investigators to determine if the habits or substances under scrutiny could help explain why one group of women developed breast cancer while a similar group did not.

The study that found parabens in tissue from breast tumors was also flawed in that it did not examine other body tissues, healthy breast tissue from the patients, or tissue from women without breast cancer for the presence of these compounds. Further, as noted in an analysis by the National Cancer Institute, this study did not show that the source of the parabens found in breast tissues was indeed antiperspirants or deodorants.

News outlets that covered this story, as noted above, were usually responsible about indicating the preliminary nature of the evidence, and typically provided information or quoted other researchers who disagreed with the conclusion that deodorants/antiperspirants caused breast cancer. Yet, one might ask, given the inconclusive nature of the studies raising the specter of such a link, why they were covered in the first place? Surely headlines such as “Study: Deodorant link to breast cancer?” or “Deodorants, shaving could cause breast cancer” give the impression that there is solid reason to believe these speculations are meaningful. The public would be better served if the media gave less space to studies that were either poorly designed or too small to be meaningful in and of themselves.

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