Parabens, oestrogenicity, underarm cosmetics and breast cancer: a perspective on a hypothesis.

A recent review by Darbre (2003) published in this journal (J. Appi. Toxicol. 23: 89-95) has attracted public and scientific interest that requires perspective, particularly on the use of esters of p-hydroxybenzoic acid (parabens) as preservatives in underarm cosmetics. Although parabens are generally regarded as safe, recent reports suggest that they are oestrogenic in a variety of in vitro (including MCF7 and ZR-75-1 human breast cancer cell lines) and in vivo tests for oestrogenicity (uterotrophic assays in both rat and mouse). There are also recent reports of adverse reproductive and developmental outcomes in rodent toxicity studies. Of interest is the lack of activity by the oral route but clear activity by the subcutaneous and topical routes, which is of some relevance to the use of underarm cosmetics. There would seem to be a case now to supplement these emerging toxicity data with longer term regulatory standard tests examining other oestrogenic endpoints and at least to consider these findings in more up-to-date risk assessments specific for cosmetic use. Further, there are few data on the use of underarm cosmetics and the risk of breast cancer, and although one recent retrospective interview-based study found no association there is a need for more thorough investigation taking into account the type of chemicals used. Darbre has forwarded a hypothesis and called for further work to establish whether or not the use of underarm cosmetics (particularly containing oestrogenic formulants) contributes to the rising incidence of breast cancer. It would seem prudent to conduct this work because the current database is sparse and the effects of long-term low-level exposures to weakly oestrogenic chemicals on human health, particularly their application to the underarm and the risks of breast cancer, are unknown. The role of oestrogens in breast cancer, however, is undisputed.