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David Bradley ISSUE #53
March 2006

An Underarm Review

Philippa Darbre of the University of Reading, England, has published a review of the putative health effects of organometallic compounds that mimic estrogen and could increase the burden of "aberrant oestrogen signaling within the human breast". Of particular relevance to public health is her suggestion that the aluminum compounds used in the manufacture of underarm antiperspirants may somehow be involved in an increased risk of breast cancer. The paper is already causing a stir in the UK, however, it is also causing controversy particularly because it does not represent any new experimental evidence but draws new conclusions from other studies.

?? Photo by David Bradley

"Since estrogen is known to be involved in the development and progression of human breast cancer, any components of the environment that have estrogenic activity and which can enter the human breast could theoretically influence a woman's risk of breast cancer," says Darbre. Her conclusion is based on the idea that aluminum salts in antiperspirants are a major source of exposure to aluminum in humans. It is commonly sprayed or rolled into armpits, which, Darbre says, inadvertently concentrates exposure near the breasts. In addition, it is often applied immediately after shaving, when the skin is likely to be damaged and less able to keep the aluminum out. "It is reasonable to question whether this aluminum could then influence breast cancer," says Darbre.

Philippa Darbre ??

However, director of the UK's Cosmetic, Toiletry & Perfumery Association, Ltd., Dr Chris Flower, has published a riposte to the research highlighting several logical flaws in Darbre's argument. "Understandably there is concern about the incidence of breast cancer," he says in the document, "and while we welcome any research that tries to determine a cause for breast cancer cases, the article may cause alarm if it is taken out of context. It is crucial to bear in mind that it is not based on new research or evidence. Darbre presents a theory and calls for further research."

Moreover, a number of leading cancer research organizations have stated there is no plausible biological mechanism by which antiperspirants could cause breast cancer. Indeed, whereas Darbre claims antiperspirants are a major source of exposure to aluminum, we are exposed to aluminum from dozens of other sources - food, water, pharmaceuticals, and environmental exposure. Aluminum is the third most naturally abundant element.

In addition, Darbre claims in her paper that, "Evidence is mounting that the aluminum-based compound[s] can break through the skin." However, these products are manufactured to work on the surface of the skin and are formulated specifically so that they are not absorbed. If they were not, they would not be effective and consumers would not buy them.

?? Could aluminum and paraben form a metalloestrogen? (Structure by David Bradley)

Finally, the CT&PA questions the theory that the organoaluminum compounds with which Darbre's review is concerned are harmful estrogen mimics. Scientists are yet to find evidence that estrogen mimics can harm human health. There are countless substances that mimic estrogen and we have been exposed to such compounds in our diets for millennia. Indeed, estrogen mimics are found at much higher concentrations in the foods we eat than the aluminum compound on which Darbre's theory hinges. "In practice, just because something has the potential to mimic a hormone (in this case oestrogen), it does not mean that it can cause harm to human health," says Flower in his document.

The only serious epidemiological study was published in 2002 by Dana Mirick of the Fred Hutchinson Cancer Research Center in Seattle, and colleagues. According to Mirick, "The rumor that antiperspirant use causes breast cancer continues to circulate the Internet. Although unfounded, there have been no published epidemiologic studies to support or refute this claim." She and her colleagues carried out a population-based case-control study to investigate a possible connection between underarm antiperspirants and breast cancer risk in women aged 20 to 74 years. They found no increased risk of breast cancer in the women even those who shaved underarm prior to applying the product. "These findings do not support the hypothesis that antiperspirant use increases the risk for breast cancer," they concluded.

According to Dr Kat Arney, cancer information officer at Cancer Research UK, "...the main risk factors for breast cancer are age, reproductive history and a strong family history of the disease." Other factors, such as excessive alcohol consumption, hormone replacement therapy, and menopause weight gain can also increase a woman's risk of breast cancer. She adds that, "In the case of deodorants and breast cancer, there is little scientific evidence to link the two. This [Darbre's] paper does not present any new data to show that these products can cause cancer, but suggests that more work should be done."

J Appl Toxicol, 2006, in press; http://dx.doi.org/10.1002/jat.1135

J Natl Cancer Inst, 2002, 94, 1578-1580; http://jncicancerspectrum.oxfordjournals.org/cgi/content/full/jnci%3b94/20/1578