The idea that aluminum in antiperspirants could cause breast cancer has been a decades-long debate. Throughout the years it has been shown that aluminum indeed acts as a metalloestrogen. Researchers have also found levels of aluminum to be higher in the tissues of women who had cases of breast cancer than not. But never before had it been shown to initiate tumor growth in breast cells–until now.
A study published in September 2016 in the International Journal of Cancer was able to demonstrate that aluminum — in levels commonly found in breast tissue–can transform healthy breast epithelial cells in to metastatic tumors.
Researchers also tested lung cells, brain cells, and bone cells and confirmed aluminum-caused mutations.
“In the large majority of commercial antiperspirants, aluminium is present as AlCl3 or, more frequently, as aluminium chlorohydrate (Al2Cl(OH)5) at concentrations up to several molar units. In aqueous solutions at pH 7.0, both salts yield aluminium hydroxide and they are absorbed through the human and mouse skin. It is, therefore, conceivable that the daily application of antiperspirants to the skin of the underarm represents a major source of exposure of the human mammary epithelium to aluminium. Although aluminium concentrations in the body are generally low, levels measured in the breast area are significantly higher.”
“Our findings demonstrate for the first time that concentrations of aluminium in the range of those measured in the human breast fully transform cultured mammary epithelial cells, thus enabling them to form tumors and metastasize in well-established mouse cancer models. Our observations provide experimental evidence that aluminium salts could be environmental breast carcinogens.”
Also of note, crystal deodorants, marketed as a safer or more natural alternative to commercial antiperspirants, also contain aluminum. Crystal deodorants are made up of either ammonium alum or potassium alum, the full names of which are ammonium aluminum sulfate and potassium aluminum sulfate, respectively. As you wet a crystal deodorant with water, the ions of the salt are released, including ionic aluminum which can also hydrolyze to aluminum hydroxide–the same form discussed as being potentially problematic in commercial antiperspirants above.
Sources:
http://onlinelibrary.wiley.com/store/10.1002/ijc.30393/asset/ijc30393.pdf;jsessionid=9159453F119E9AB711B0E1A85853F946.f04t03?v=1&t=ixtj8fnv&s=d81366bc06af8dcea017f382f31d240f2041cce6
http://www.madsci.org/posts/archives/2013-10/1382676811.Bc.r.html