WASHINGTON — A new plastics industry study found that a key building block of polycarbonate is not an endocrine disrupter at very low doses, a conclusion that disputes research that had raised troublesome questions for the plastic.
The study from the Society of the Plastics Industry Inc. found that the building block, Bisphenol A, does not increase prostate weights or decrease sperm counts in male mice. SPI and the Bisphenol A Sector Group of the European Chemical Industry Council sponsored the study, which was released Oct. 15.
Two earlier studies from the University of Missouri had found larger prostates and decreased sperm counts at doses much lower than previously considered dangerous, lending support to a controversial theory known as the ``low-dose hypothesis.''
If that research would have been duplicated, it meant the ``margin of safety'' for BPA would be much less than previously thought for consumer products, said John Waechter, a Dow Chemical Co. scientist and a member of SPI's BPA task force who presented the results.
The study supports the current standards for BPA exposure, SPI officials said.
SPI officials said they could not explain why results would differ, but said their study tested many more animals than the earlier research: 548 male offspring of mothers dosed with BPA, compared with 25 male offspring in an earlier Missouri effort.
``Our goal was to increase the statistical power of the study,'' Waechter said. ``We wanted to make this a more statistically powerful study than the previous studies.''
James Lamb, an environmental consultant who reviewed the Oct. 15 study for Washington-based SPI, said that one of the earlier studies, by University of Missouri Professor Fred vom Saal, has been a pivotal study in endocrine research. ``It is much more important that a larger study has not been able to reproduce it,'' Lamb said.
Vom Saal could not be reached for comment.
BPA is used in making PC and epoxy resins, including can coatings. SPI said the chemical has weak estrogenic effects, and the federal government set limits on daily human exposure in 1983.
BPA is part of an Environmental Protection Agency test of endocrine disrupters. More industry tests looking at effects over several generations and at larger doses are under way, SPI said.