Chemicals known as parabens, which may have a role in breast cancer and are commonly used as preservatives in cosmetics, food products, and pharmaceuticals, have now been found in measurable levels in the breast tissue of women who do not use underarm products.

Studies dating back as far as 1998 had begun to indicate that parabens (alkyl esters of p-hydroxybenzoic acid) might possess estrogenic properties, and estrogen is known to play a central role in the development, growth, and progression of breast cancer. When parabens were found in breast tumor tissue in 2004, the possibility was raised that these substances entered the tissue by means of low-level dermal absorption from personal-care products applied to the breast region.

In the current study, paraben concentrations were measured at four locations across the breast from axilla to sternum using 160 tissue specimens. The tissue was collected from 40 mastectomies for primary breast cancer performed on women in England between 2005 and 2008.

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Nearly all (99%) of the samples contained at least one paraben, and 60% had five. Notably, the chemicals were found in 7 of the 40 patients who reported never having used an underarm product.

“Our study appears to confirm the view that there is no simple cause-and-effect relationship between parabens in underarm products and breast cancer,” remarked investigator Lester Barr, consultant surgeon at the University Hospital of South Manchester at Wythenshawe Hospital in Manchester, United Kingdom, and chair of the Genesis Breast Cancer Prevention Appeal, which partially sponsored the study and is also based at Wythenshawe Hospital. “The intriguing discovery that parabens are present even in women who have never used underarm products raises the question: Where have these chemicals come from?”

As Barr and colleagues reported in Journal of Applied Toxicology, the overall median value for total parabens in the breast tissue was four times higher than the level recorded in the 2004 study. There was a disproportionate incidence of breast cancer in the upper outer quadrant nearest the armpit, and significantly higher levels of n-propylparaben in the axilla region (closest to the armpit) than in the mid or medial regions. The other four parabens were equally distributed across all parts of the breast.

The investigators found no correlations between paraben concentrations and patient age (37 to 91 years), length of time spent breastfeeding (0 to 23 months), tumor location, or tumor estrogen-receptor content.