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Common Plastic Ingredient May Be Cause for Concern
8 August 2007 (All day)
ALEXANDRIA, VIRGINIA--A federal advisory panel meeting here today concluded that a hormonelike chemical found widely in food containers, bisphenol A, could potentially be causing neurological effects in fetuses and children. Although the group's conclusion, based on a wealth of animal and human studies, falls short of supporting any kind of ban, the panel expressed "some concern" about the chemical and noted that people may want to reduce their exposure.
That conclusion didn't satisfy environmentalists and some scientists. The report "dramatically understates" the risks, claimed the Natural Resources Defense Council, which has accused the government, academic, and industry scientist-composed panel of a pro-industry bias.
Bisphenol A is a plastic ingredient found in many food containers, from baby bottles to the linings of food cans. Small amounts can leach out into food, and the chemical has been detected in the blood of most North Americans tested. The minuscule (parts per billion) levels are well below the safe exposure level set in the 1980s by the Environmental Protection Agency (EPA). A decade ago, however, neurobiologist Frederick vom Saal's group at the University of Missouri, Columbia, reported that even very low levels of this so-called endocrine disruptor fed to pregnant mice could cause changes in the prostate glands of their male offspring. The study was controversial--some industry-funded studies couldn't replicate it--but an expert panel concluded the results were valid (Science, 27 October 2000, p. 695).
Since then, many other scientists have reported low-dose effects in rodents, and some epidemiology studies have suggested links between bisphenol A and health effects in people. To assess these risks, the National Toxicology Program's (NTP's) Center for the Evaluation of Risks to Human Reproduction (CERHR) formed an expert panel that met in March and this week to assess more than 500 studies.
The reviewers rejected many of the low-dose animal studies because of design problems, such as injecting the chemical, which bypasses metabolic processes that detoxify much of it when it is ingested. But the panel found compelling about a half-dozen reports of neurological and behavioral effects in rodents exposed to bisphenol A in the womb, such as changes in brain structure and in how often mothers lick their offspring. The levels of bisphenol A that caused these changes in animals "are pretty close to where humans are exposed," said panel chair Robert Chapin of Pfizer Inc.
The panel wasn't asked to offer recommendations about what regulatory agencies should do. However, "this might be a time for the application of the precautionary principle," said Chapin. That is, explained CERHR director Michael Shelby, people may want to consider "alternatives" to containers made with bisphenol A.
Still, critics accused the panel of ignoring many other relevant studies. They point out that 38 bisphenol A experts and other scientists who met at a workshop last November concluded that people are exposed to doses that cause many other effects in animals, such as enlarged prostate and larger body size. The consensus statement of the November group, which is in press at Reproductive Toxicology, describes "a great cause for concern with regard to the potential for similar adverse effects in humans."
The NTP advisory panel's report will next go out for public comment. Then the NTP itself will issue a statement that will be peer-reviewed. It's unclear at this point how regulatory agencies, such as the Environmental Protection Agency, might respond to the report.