Mature human egg (ovum) x260

Toxins love to get you while you’re young. Lead, mercury, secondhand smoke and sundry other environmental nasties do a lot more damage when tissue is immature, vulnerable and growing than when it’s mature and comparatively fixed. Now, according to a small new study led by the University of California, San Francisco (UCSF), the endocrine disruptor BPA may have the longest reach of all — damaging a woman’s ova before a baby can even be conceived, much less born. (More on Time.com: Dirty Money? Traces of BPA Found on Currency)

As epidemiologists and environmental scientists are increasingly learning, the toxicity of BPA may be rivaled only by its ubiquity. A chemical used in the manufacture of plastics, bottles, toys, container liners and much more, it is present in uncountable numbers of household products — and the bloodstreams of uncountable numbers of human beings too. In a 2004 study, scientists at the Centers for Disease Control and Prevention (CDC) found traces of BPA in 93% of 2,517 subjects tested. That’s bad news, since the chemical has been linked to neurological disorders, hormonal disruptions, cancer and genital abnormalities in newborn boys.

In 2007 and 2008, UCSF researchers were conducting a large-scale study of the effect toxic metals, including mercury, cadmium and lead, on human reproduction. In the course of their work, the investigators also decided to study a small subgroup of 26 women undergoing in vitro fertilization (IVF) — looking specifically at the impact BPA had on the success of the procedure. As their study, newly published in the journal Fertility and Sterility, reveals, they got an unpleasant surprise. (More on Time.com: Study: IVF Causes Higher Rates of Baby Boys)

Higher blood levels of BPA, they found, were linked to a 50% reduction in normal fertilization of eggs after they were retrieved for IVF. Though it wasn’t clear just what the mechanism was that was getting in the way of fertilization, previous studies do offer some clues. Animal experiments, for example, have shown that exposing female mice to BPA can damage the genetic make-up of their eggs. If that holds for humans too, it could be a problem that affects millions of women.

“Given the widespread nature of BPA exposure in the U.S.,” said Michael Bloom, an assistant professor in environmental health science at the University of Albany and a co-author of the paper, “even a modest effect on reproduction is of substantial concern.” (More on Time.com: 5 Pregnancy Taboos Explained (or Debunked))

The problem, of course, is that that same widespread nature makes BPA almost impossible to avoid. The Department of Health and Human Services and other government agencies offer tips for at least reducing exposure by choosing alternative products, and UCSF has launched an online service offering similar advice. Until the chemical is taken out of the products, the least we can do is keep some of the products out of our lives.

Related Links:

Canada Declares BPA Toxic. Is the U.S. Next?

Study: Could Cell-Phone Use in Pregnancy Affect Kids’ Behavior?