In an article published on May 20, 2016 in the peer-reviewed journal Environmental Health Perspectives, Roberto Pastor-Barriuso and colleagues from the National Center for Epidemiology, Carlos III Institute of Health, Madrid, Spain, examine the association between blood levels of xenoestrogens and breast cancer risk in Spanish women.

The analyses were done not only for single compounds determined by chemical analysis, but also for a total effective burden of xenoestrogens, measured as a biological response in MCF-7 breast cancer cell line. As this cell line is derived from an estrogen-dependent tumor, this in vitro test estimates the estrogenicity based on the compound’s or mixture’s capacity to induce cell proliferation.

It has been argued previously that epidemiology should focus on mixtures of compounds rather than on individual chemicals. Following this approach may be particularly crucial when evaluating compounds with similar actions (FPF reported). Pastor-Barriuso and colleagues have now provided compelling experimental evidence that this is indeed the case: While a strong positive association was found between total xenoestrogen burden and breast cancer risk, only “weak and opposed” associations were observed for individual xenoestrogens. These findings highlight the importance of studying the mixtures rather than single compounds, at least for hormone-related diseases, in epidemiology.


Pastor-Barriuso, R. et al. (2016). “Total effective xenoestrogen burden in serum samples and risk for breast cancer in a population-based multicase-control study in Spain.Environmental Health Perspectives (published online May 20, 2016).

Braun, J.M. et al. (2016). “What can epidemiological studies tell us about the impact of chemical mixtures on human health?” Environmental Health Perspectives 124:A6-A9.