Thirty-eight independent US scientists have expressed “great cause for concern” that adverse effects seen in laboratory animals exposed to the plastics intermediate bisphenol A may also be occurring in humans.
Bisphenol A is used to make epoxy resins and polycarbonate plastics. About 2.8 million tonnes are produced each year and humans are exposed through the environment and its use in applications such as can linings, bottles and dental sealants.
The statement, to be published in the journal Reproductive Toxicology, emerged from a meeting on bisphenol A held in Chapel Hill, South Carolina, in November.1 The process was funded by US national medical research agency, the National Institutes of Health (NIH). The statement will also supported by five peer-reviewed papers on different aspects of bisphenol A exposure and toxicology in the same journal.
The effects of concern in laboratory animals include abnormal male genital development, early puberty in females, neurological problems, obesity and type 2 diabetes. The researchers say current human exposure levels may be sufficient to cause similar effects.
But another, more influential, scientific panel – also funded by the NIH – has come to a different conclusion. The Center for the Evaluation of Risks to Human Reproduction (CERHR), which reports to the US Health Department’s National Toxicology Program (NTP), released an interim statement on 6 August expressing “some concern” over potential neurological effects of bisphenol A, but “minimal concern” over reproductive effects and “negligible” concern over birth defects.2The CERHR’s announcement came from its expert panel on bisphenol A, which is due to finalise its report this autumn. However, director Michael Shelby told ENDS: “The panel is finished with its work and the conclusions will not change.”
Dr Shelby was at a loss to explain how the two groups of scientists could come to such divergent opinions, noting that the panel “went through a well established process designed to reach an official position”. The report will become the government’s official position when it is backed up by an NTP monograph, he added.
But the Chapel Hill scientists and environmentalists have accused CERHR’s panel of industry bias, failure to include people with sufficient background in the toxicology of bisphenol A and errors in the science. Unlike the Chapel Hill group, it includes members employed by major companies. The chairman works for Pfizer, while another member is employed by another pharmaceutical company, Schering-Plough.
The Environmental Working Group, which campaigns on chemicals issues, revealed earlier this year that the consultants CERHR hired to compile the report, Sciences International, had financial links to bisphenol A manufacturers (ENDS Report 386, pp 28-29 ). EWG continues to follow the issue closely and has catalogued 297 errors in the CERHR report, many spotted by Chapel Hill scientists.
Professor Fred vom Saal of the University of Missouri-Columbia, a leading member of the Chapel Hill group, criticised the lack of experts on the panel: “The ‘expert panel’ label is false,” he said. “It was put together explicitly from people who have not had contact with this [bisphenol A] literature before. How could they go through the 700 articles referenced? They have day jobs.”
Associate director of the National Toxicology Program, John Bucher, dismissed accusations of bias and said a choice had been made on criteria for inclusion in the review which “tended to include studies done for regulatory purposes and exclude others”.
But he added that the panel’s report would not be the organisation’s final word on the risks of bisphenol A. “What we have is a working group which has expressed an opinion. What we then do is take that and develop an NTP opinion.” The process might involve the inclusion of other primary research and the Chapel Hill statement “will be considered”, he said.
Despite the shortcomings, Professor vom Saal was upbeat about some CERHR conclusions. “A government panel has come out and said that bisphenol A poses a risk. Some members of the panel succeeded in throwing out the studies showing reproductive effects, but they could not throw out the neurotoxicity studies.”