InsideEPA.com, Maria Hegstad
Published January 22, 2008
Environmentalists will soon present a new study to the National Institute of Environmental Health Sciences (NIEHS) to support their argument that an NIEHS assessment of the widely used plasticizer bisphenol-A (BPA) improperly excluded key studies that strongly link the chemical with reproductive risks.
The activists hope the new study will persuade an NIEHS panel that will issue a final report on BPA this summer to include the previously rejected studies.
NIEHS’ final position on BPA, written by its National Toxicology
Program (NTP), could impact EPA’s assessment of BPA. EPA will assess BPA this year for its Integrated Risk Information System (IRIS), a database of toxicity values used by federal and state environmental protection programs.
BPA, which is used in sunglasses, compact disks, plastic containers for food and water and other products, has generated controversy because studies have shown significant human exposure to the chemical. The plastics industry has argued that such exposures do not pose health risks, but environmentalists and others have cited studies showing a variety of adverse effects.
At issue is a report published last year by panelists convened under the auspices of the NTP’s Center for the Evaluation of Risks to Human Reproduction (CERHR) to evaluate BPA’s reproductive risks. In conducting their evaluation, the CERHR panelists chose to omit numerous studies because they thought the sample size was too small or disagreed with the how the experiments were conducted, explain sources with the Environmental Working Group (EWG) and the Natural Resources Defense Council (NRDC).
The excluded studies, however, were among those that showed the strongest link between BPA and such effects as reproductive toxicity, reproductive cancers, obesity and pre-diabetic conditions, the NRDC source says.
The CERHR report found that BPA presents some “neural and behavior risks” in fetuses, infants and children but downplayed other reproductive risks, including the potential for accelerating puberty and causing birth defects. The panel reviewed only the substance’s reproductive risks rather than its overall health impact potential.
In contrast with the CERHR findings, another NIEHS panel called the Chapel Hill group found that the substance presents significant risks and should be further assessed. Its report warned: “much evidence suggests that . . . adverse effects are occurring in animals within the range of exposure to BPA of the typical human living in a developed country.”
CERHR is putting together the NIEHS monograph, or final position, on BPA, says an NIEHS spokeswoman. It is expected to be complete this summer. In developing the final report, staff must try to synthesize the two reports, together with public comments, and review literature published since the reports were written, says a senior CERHR official. The final position will be sent to other federal agencies, including EPA.
EWG and NRDC in comments they will submit to the CERHR staff will cite a study by Frederick vom Saal of the University of Missouri-Columbia -- a well-known researcher in the field of endocrine-disrupting chemicals -- to be published this month in the journal Reproductive Toxicology. It makes the case that BPA studies previously excluded should be considered in the weight of evidence concerning BPA’s reproductive toxicity.
The two NIEHS groups -- CERHR and the Chapel Hill group -- probably came to such different conclusions because they used different processes, says the senior CERHR official. The CERHR panel set up criteria for evaluating existing studies and literature on BPA, and those criteria gave less weight to animal studies that did not dose the subjects by mouth.
EWG’s comments will urge CERHR to reconsider that analysis in light of vom Saal’s new study, which found that baby mice dosed with BPA orally or by injection tested positive for similar amounts of the chemical in their blood. The implication is that non-oral dosing studies should not have been excluded when CERHR conducted its BPA assessment.
The vom Saal study, if accepted in the final NIEHS position paper, could impact EPA’s BPA assessment. BPA was among a score of chemicals nominated for the agency to review and add to its IRIS database in 2008.
EPA’s Office of Policy, Economics and Innovation recommended BPA for inclusion in the IRIS agenda for 2008. “It was clearly receiving lots of attention and the assessment was out of date because there have been so many new studies,” says an agency risk assessor.
