Facebook certainly leads me to read papers that I normally wouldn't.
For whatever reason, a post about deodorants popped up on my feed, from the Wendyl's Green Goddess page. In the blurb for a sale of products was the following:
Conventional products contain aluminium ingredients which have been linked to cancer. Do your skin and body a favour and switch to a 100% natural, aluminium-free deodorant optionA.
It sounds like a rather nice product, but the claim that the aluminium compounds found in conventional antiperspirants are linked to cancer caught my eye. After all, aluminium is pretty much everywhere in the environment in various forms, & has been for billions of years; we've evolved with it there. So I asked for a citation to support the claim. Rather to my surprise (because often, when I ask, I don't get), a reference was provided
I thought it a little odd that this paper - claiming a link between aluminium, antiperspirants, and breast cancer - was published in the Journal of Inorganic Biochemistry and not in a journal focused on oncology. Greater bloggers than I have noted that this journal does seem to have a thing for papers that make various claims about the purported links between aluminium and various health concerns. (I encourage reading the post at that link; it is both entertaining and highly informative.)
Back to that citation. It states that there is "a disproportionately high incidence of breast cancer in the upper outer quadrant of the breast", which the author sees as evidence in support of his aluminium hypothesis. He also notes that aluminium is absorbed across the skin in mice in experimental situations, but provides no evidence that this happens in the underarm/breast area in humans. Sounds scary, though.
However, an even greater blogger (a research scientist who is also a surgeon specialising in breast cancer, and who goes by the 'nym of OracB) has examined this paper and found it ... wanting. He's written extensive commentaries on the subject on his blog, but I did a quick summary on the original FB post: basically, the claim that more breast cancers originate in the region of the breast closest to the armpit is wrong. The incidence is slightly over 50%, but that's down to anatomy - there is more actual breast tissue in that quadrant than in the others. Once that's allowed for, there are no more cancers in that breast region than in any other part of the breast. Unfortunately this hasn't stopped various scaremongering sites from running with the story, as discussed here by Orac.
To my amusement, on the very same pubmed page as that first citation is a link to a systematic review (one of many) that found no relationship between aluminium & breast cancer:
The expert group's conclusion coincides with those of the French, European and American health authorities. After analysis of the available literature on the subject, no scientific evidence to support the hypothesis was identified and no validated hypothesis appears likely to open the way to interesting avenues of research.
tl;dr: there is no evidence to support any causal link for the claims that antiperspirants cause breast cancer. Perhaps such products should be sold on the basis of their merits, rather than ill-founded fears.
A There is some irony in the fact that the aluminium-free product is sold in ... aluminium containers.
B Orac's identity is pretty much an open secret among those who follow his blog.