BPA DEFENSE: The levels of BPA that people are exposed to are thousands of times lower than the threshold that EPA has determined to be safe.
TRUE, BUT: Just because human exposure is below the EPA threshold doesn't mean we're safe. The EPA standard, established in the 1980s, is based on traditional toxicology rather than endocrinology. BPA is a synthetic hormone, which means tiny doses — in the parts-per-billion range — may be dangerous too.
BPA DEFENSE: Most of the evidence of adverse health effects comes from rat and mouse studies.
TRUE, BUT: Animal experiments are crucial in toxicology. (Scientists don't feed humans potentially harmful chemicals.) Small mammals such as rats and mice are accepted as a proxy, because their biology is similar to ours. And since people are exposed to BPA in their daily lives, there is a growing body of human data that support what lab scientists are finding. But the data will never be definitive because it's impossible to find a control group of humans with no BPA exposure.
BPA DEFENSE: Industry-funded studies — which show no adverse effects from BPA in rats and mice — are larger than the independent studies, so they are more statistically significant.
TRUE, BUT: Even large studies can be flawed. Academics and government BPA researchers tend to conduct smaller studies to stretch their grant dollars, but these too can achieve statistical significance. Several industry studies have flaws that cast doubt on their conclusions.
BPA DEFENSE: Industry-funded studies are better because they comply with Good Laboratory Practices.
MISLEADING: GLP is a record-keeping protocol designed to prevent fraud at labs that have a financial stake in the outcome of their experiments. Independent scientists don't use GLP; instead they are scrutinized by peer reviewers, grant administrators, and journal editors.
BPA DEFENSE: Studies showing harm from BPA have not been replicated.
UNTRUE: The primary target of this criticism, biologist Frederick vom Saal, has had his experiments replicated by many other researchers. While a few studies have failed to find low-dose harm from BPA, many more have shown a panoply of effects.
A version of this article appeared in the February 2009 issue of Fast Company magazine.