Parabens and breast cancer: Controversial preservatives found in almost all breast tissues

The apparent link between parabens and breast cancer

It was in 2004 that researchers reported the occurrence of a series of compounds known as parabens in human breast cancer tissue, sparking a debate about the function of these compounds and their potential role in breast cancer. This report triggered numerous other studies that also implicated parabens without providing any definitive proof of their involvement.

These controversial compounds are alkyl esters of p-hydroxybenzoic acid which are added as antimicrobial preservatives to pharmaceuticals, foods and personal care products like shaving gels, body lotions, antiperspirants and moisturisers. They have since been measured in blood, urine and human milk and have been shown to enter the bloodstream intact following the topical application of cosmetic creams.

The parabens are of concern because they have estrogenic effects. Most breast cancers feed on estrogen and therapies can involve reducing its circulating levels, so this has been taken as further support for the involvement of parabens in breast cancer. It was suggested that application of underarm deodorants would allow parabens to be absorbed into the breast due to the close proximity. This appeared to be borne out by the fact that many breast cancers form near the axilla.

One problem with the original study was its small sample size with only 20 samples of breast cancer tissue tested. Now, the lead author of that study, Philippa Darbre from the University of Reading, has extended the work by examining 160 samples from 40 patients with breast cancer who had been given mastectomies. She teamed up with surgeons Lester Barr and George Metaxas from the University Hospital of South Manchester NHS Foundation Trust, and Christopher Harbach and Luc-Alain Savoy from SGS M-Scan.

Parabens everywhere

The tissue sections were taken from non-cancerous parts of the breast at four positions from the underarm area (axilla) to the sternum (breastbone). The parabens were extracted from each sample and analysed by LC/MS with atmospheric pressure chemical ionisation in negative-ion mode and tandem mass spectrometry. Five parabens, the methyl, ethyl, propyl, butyl and isobutyl esters, were measured individually.

The results were surprising. Nearly all of the samples, 158 out of 160, contained at least one of the parabens, no matter where the tissue was located within the breast. So, does this support the suggestion that underarm deodorants/antiperspirants containing parabens are responsible for the cancers? Well, there is still no clear answer to that question, because 7 of the 40 women declared that they had never used these products. So, if the parabens are responsible they must have come from other sources too.

A comparison of the paraben concentrations across the breast showed that there were no consistent differences for each paraben, which again argues against them having a major involvement. Also, high levels of one paraben in one particular location were not matched always by high levels of the other esters. "Our study appears to confirm the view that there is no simple cause and effect relationship between parabens in underarm products and breast cancer," said Barr.

The fact that the majority of breast cancers occur in the top quadrant of the breast near the armpit region could have nothing to do with cosmetics. It just happens to be the area with the highest concentration of fatty tissue. Many other lipophilic and hydrophilic compounds have been discovered in breast tissue.

So, although the parabens have been found in the majority of breast tissue samples tested in this research project, any causal relationship between some or all of them and the development of breast cancer remains to be determined.

Darbe has been widely quoted as saying "The fact that parabens were detected in the majority of the breast tissue samples cannot be taken to imply that they actually caused breast cancer in the 40 women studied. However, the fact that parabens were present in so many of the breast tissue samples does justify further investigation."

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.