Newest estrogen mimics the commonest?

Phthalates, compounds best known for their ability to make plastics flexible, are the most abundant industrial contaminants in the environment. Two new studies now demonstrate that at least a couple of them possess a hormonal alter ego: They activate receptors for estrogen, the primary female sex hormone.

Both studies also established the estrogenicity of BHA, a preservative commonly added to food to retard rancidity.

In recent years, scientists have been compiling a list of emasculating agents that work by mimicking estrogen. Susan Jobling of Brunel University in Uxbridge, England, and her colleagues collared the three new prospects while assaying 20 common sewage contaminants. They were scouting sources of the estrogenicity that teammate John P. Sumpter had observed in wastes from sewage-treatment plants (SN: 1/8/94, p.24).

Nine of these pollutants bind to estrogen receptors. The researchers incubated cells with each of the nine to see whether any of them triggered the receptor's normal activity. BHA, butyl benzyl phthalate (BBP) and di-n-butyl phthalate (DBP) not only appeared estrogenic, but also stimulated the growth of breast cancer cells in culture, the group reports in the June Environmental Health Perspectives.

At the same time, researchers at Tufts University School of Medicine in Boston and the University of Granada in Spain were studying some of the same compounds. Their findings, to be published in the same journal later this year, also identify BHA and BBP as estrogens. However, while DBP did not exhibit estrogenicity in their assays, a third plasticizer--diphenyl phthalate--did.

Where does one find phthalates? DBP serves as a dispersant in some insect repellents and appears in plastic plumbing pipes and food wraps. Indeed, the British team cites studies finding up to 500 micrograms of DBP per kilogram of food wrapped in plastic. BBP goes into vinyl floor tiles, adhesives, synthetic leather, and the papers and cardboard designed for contact with liquid, dry, and fatty foods. That last application may explain how butter and margarines end up laced with BBP at concentrations exceeding 45 milligrams per kilogram, as cited in "Male Reproductive Health and Environmental Chemicals with Estrogenic Effects," a new report by the Danish Environmental Protection Agency in Copenhagen.

No one knows if the newly unmasked environmental estrogens pose a risk to humans or wildlife. Jobling's team points out that our bodies may readily deactivate or break down the compounds.