NTP brief on BPA receives mixed peer review
Peer reviewers of a federal agency’s draft brief on bisphenol A recommend lowering levels of concern for some human-health risks.
Less than 2 months after the U.S. National Toxicology Program (NTP) released its much-awaited draft brief on the human-health risks of bisphenol A (BPA), the agency’s board of scientific advisers gave the report a somewhat mixed review. In a meeting held on June 11, the experts agreed with NTP’s concern over some of BPA’s human-health impacts. But, citing a lack of sufficient evidence, the board members suggested that NTP lower the levels of concern for two of the health risks of this estrogen-like chemical. The advisory board also pointed to a missing part of the BPA puzzle—exposure data for those most vulnerable to BPA: fetuses, infants, and children.
|Manufacturers, including Nalgene, and retailers Wal-Mart and Target have responded to public concern by withdrawing certain BPA-containing products, such as baby bottles, from stores.
This is the latest chapter in the ongoing saga over this high-production-volume chemical. Used in polycarbonate plastics and epoxy-based resins, BPA is found in many consumer products, including baby bottles, reusable plastic bottles, dental sealants, and even the dyes on credit-card receipts.
According to data collected by the U.S. National Health and Nutrition Examination Survey (NHANES), 93% of Americans 6 years and older have BPA in their bodies. “It’s pretty amazing that we are seeing detectable levels in everyone,” notes Katherine Hammond, a member of NTP’s scientific advisory board and a public-health expert at the University of California Berkeley.
Although BPA’s toxic impacts on human development and reproduction at high doses are undisputed, its low-dose effects are highly controversial.
Different panels and organizations have reviewed BPA’s low-dose effects and arrived at varying conclusions. Last summer, a National Institutes of Health panel concluded that the evidence shows that some of the adverse effects are occurring “within the range of exposure to BPA of the typical human living in a developed country.” Another panel, convened by the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR), concluded that available scientific evidence pointed to “some concern” for neural and behavioral effects in pregnant women, fetuses, and children. NTP uses a five-point scale of “negligible” to “serious” to rate “concern”.
However, the CERHR panel has been at the center of much debate. It drew severe criticism for hiring a contractor who had worked for chemical manufacturers to draft the CERHR report. NTP fired the contractor, Sciences International (SI), but the panel included the work done by SI in its final report. Researchers and environmental groups have also criticized the panel’s inclusion of two nonpeer-reviewed studies funded by the American Plastics Council.
And a U.S. congressional committee is investigating industry consultants; infant-formula manufacturers, for using epoxy-lined cans; and the U.S. Food and Drug Administration’s decision not to regulate BPA.
Meanwhile, in April, Canada became the first country to declare the compound toxic and ban it from use in baby bottles.
NTP released its draft brief in April. Its conclusions were not far from the CERHR panel’s results, except that it ratcheted up the level of concern for prostate, mammary, and early puberty effects from “minimal” to “some”.
Many scientists and environmentalists approved of NTP’s conclusions, but scientists representing industry groups were not pleased. In a public comment presented at the June 11 meeting, Steven Hentges, a representative of the American Chemistry Council, said that, unlike the earlier CERHR report, NTP’s evaluation was “inconsistent” and based on “inadequate studies.”
On June 11, as the board members prepared to cast their votes on NTP’s draft brief, some experts emphasized the urgent need to fill in the missing part in the BPA story. They said that the brief’s conclusions were based on current exposure data from NHANES, which did not include people at higher risk—infants and children below the age of 6, and people with liver and gut diseases, who cannot metabolize the compound.
The board agreed with NTP’s conclusions that existing scientific evidence pointed to “some concern” over neural and behavioral effects and impacts on the development of the prostate gland in male fetuses and infants. But it also recommended lowering the level of concern for mammary gland and early puberty effects of BPA to “minimal”.
It is unknown whether NTP will adopt the board’s recommendations in its final report, due to be released later this summer. Also unclear is whether NTP’s report would influence U.S. federal regulators’ decision not to regulate the chemical.