The latest study, published recently in the journal Endocrinology, compared the effects of BPA on zebrafish embryos with the effects of Bisphenol S (BPS), a common alternative used in some (though not all) plastics labeled "BPA-free."
"Back in 2007, when my lab did its first work looking at effects of BPA on embryonic development, what we saw was rather shocking to us," senior author Nancy Wayne, a reproductive endocrinologist and a professor of physiology at the David Geffen School of Medicine at UCLA, said.
Wayne saw what many endocrinologists have reported: The chemical had an immediate and profound effect on non-human embryos exposed to it.
"It scared us," Wayne said. "It scared all of us, and I couldn’t get funding from the federal government to study it." The FDA still states that the level of BPA that humans are exposed to is safe, and several other agencies across the world stand by the same conclusion. But the Endocrine Society disputes these findings.
"BPA is a huge business, huge," Wayne said. "Sometimes I wonder who the government is representing."
Wayne wasn't able to do much work on BPA without federal funding. Then along came Wenhui Qiu, a visiting graduate student from Shanghai University who wanted to study BPA and embryo development. She brought with her funding from her own government, and she and Wayne set to work exposing the embryos of zebrafish — commonly used for such experiments because their see-through embryos make it easy to observe cell growth — to BPA.
Because a few studies have suggested that the common alternative BPS might have harmful effects as well, Qiu and Wayne decided to compare the two chemicals in action.
In both sets of embryos, which were exposed to levels of BPA and BPS comparable to what one would find in a polluted river, the researchers saw an acceleration in hatching times leading to premature births. They also saw abnormal growth in the brain cells that would eventually control reproduction in the fish, as well as other signs that genes associated with reproduction were working overtime.
"We were really surprised to see how similar the responses were," Wayne said. "It was rather shocking to us."
BPS seemed to be acting as an endocrine disrupter, just as BPA did. Endocrine disrupters cause harm by mimicking, blocking or otherwise interfering with the naturally occurring chemical hormones of the body.
"It’s not the way that people think of a classic toxin, it’s not like you’re exposed and you die," Wayne explained. But many in her field are concerned that these chemicals could be tied to a whole host of human issues: Cancers of the reproductive organs, premature births, early puberty and genital malformation, just to name a few.
"The message here is that BPS is not necessarily safer," Wayne said.
The American Chemistry Council has previously expressed skepticism over BPA experiments using zebrafish, arguing that humans are only exposed to trace amounts of the chemicals through their diet and that these compounds don't accumulate in the body. And it's true: A zebrafish is not a human, and we don't know how directly human embryos are even exposed. But since ethical roadblocks prevent endocrinologists from exposing human embryos and infants to the chemicals, it's unlikely we'll get more direct evidence that these substances cause us harm.
Now that Wayne is back to having limited funding for BPA projects, she hopes other groups will continue looking at BPS.
"I don’t have funding for this, and it takes money," she said. "I’ve been supported by UCLA, and I’ll continue to do a little bit of work on this. But I’m hoping the endocrine community will pick it up and take it forward. It’s going to take the whole community."
Correction: A previous version of this article referred to comments made by the American Chemistry Council in regards to an earlier experiment using BPA and BPS. The article has been updated to clarify that the ACC only commented on the findings related to BPA, not BPS.