摘要：Bisphenol A (BPA), a synthetic chemical used in the production of plastics since the 1950s and a known endocrine disruptor, is a ubiquitous component of the material environment and human body. New research on very-low-dose exposure to BPA suggests an association with adverse health effects, including breast and prostate cancer, obesity, neurobehavioral problems, and reproductive abnormalities. These findings challenge the long-standing scientific and legal presumption of BPA's safety. The history of how BPA's safety was defined and defended provides critical insight into the questions now facing lawmakers and regulators: is BPA safe, and if not, what steps must be taken to protect the public's health? Answers to both questions involve reforms in chemical policy, with implications beyond BPA. “US cites fears on chemical in plastics” was the headline of an April 14, 2008, front-page article in the Washington Post . 1 The chemical of concern was BPA, used in the production of plastics found in numerous commercial products, including laptops, cell phones, baby bottles, water main pipes, laboratory and hospital equipment, and food containers. BPA made national headline news because of high economic, scientific, and political stakes involved in the debate about its safety. With over 6 billion pounds of BPA produced globally every year and continued growth expected in the coming years, the market for BPA is large and extensive. 2 Recent biomonitoring studies indicate that exposure to BPA is widespread, 3 , 4 and this ubiquity has raised concerns—or, as the April 2008 article noted, “fears”—regarding the health effects of exposure. A growing body of laboratory research on very low doses of BPA—levels that fall below the regulatory safety standard—reports associations with increased rates of breast and prostate cancer, chromosomal abnormalities, brain and behavioral abnormalities, and metabolic disorders. 5 In response to this new research on exposure to BPA and its health effects, state and federal lawmakers in the United States and around the world are faced with the critical question of whether BPA is safe. In April 2008, the Canadian government took a precautionary approach, classifying BPA as “toxic” under the Canadian Environment Protection Act and is considering a limited ban. 6 , 7 By contrast, the European Food Safety Authority and the US Food and Drug Administration (FDA) declared BPA safe at estimated levels of human exposure. 8 , 9 Retailers, however, chose not to wait for a regulatory decision and began pulling plastic water and baby bottles made with BPA from the shelves in 2008. In early 2009, a bill banning BPA in children's food containers was introduced in Congress. 10 The safety and future of BPA remain resolutely uncertain. There are two issues to be resolved in this current debate about BPA safety. First, what is the best available science for assessing the safety of BPA? And second, if BPA is unsafe, why was it presumed to be safe for the past 50 years and how did this understanding change? To answer these questions demands a critical examination of the historical process by which BPA's safety was defined and the ways this assumption was ultimately challenged by new scientific research.
