Patisaul2010 - Feature Articles Assessing Risks from...

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30 American Scientist, Volume 98 Feature Articles © 2010 Sigma Xi, The Scientific Research Society. Reproduction with permission only. Contact [email protected] T he industrialized world produces an immense amount of plastic, more than 45 billion kilograms annually in the United States alone. But what is it made of, and is it all safe? Some reus- able water bottles sold in Wal-Mart and other retail stores in the United States now display stickers proudly marketing themselves as “BPA-free.” The labeling results from consumer concern over sci- entific evidence that bisphenol A (BPA), a common ingredient in many hard plastics, may be harmful to the human reproductive system because it interferes with hormones. The plastics industry and the U.S. Food and Drug Administra- tion (FDA) say BPA is not dangerous at the levels people are currently exposed to. In contrast, in September of 2008, the U.S. National Toxicology Program (NTP) concluded that there is “some concern” for adverse effects on the “brain, behav- ior and prostate gland in fetuses, infants, and children.” This concern prompted members of Congress to pressure the FDA to take another look, a process that is now underway. Inconsistent messages about BPA safety have generated considerable public rancor, highlighting how hu- man risk assessment of BPA (and com- pounds like it) is both uncoordinated and controversial. Consensus regard- ing BPA’s safety has evaded U.S. health agencies for multiple reasons. Most pressing is the lack of clear guidelines for how much or what type of scientific evidence is needed to judge risks from hormone-disrupting compounds such as BPA. It would be unethical to direct- ly assess those risks in people through controlled, double-blinded exposure experiments. At the same time, there are uncertainties about when exposure data from animal studies are relevant to human health. In a global environment where BPA production and exposure have grown rapidly, there is a pressing need to overcome these challenges. That is especially true because BPA is only one of thousands of chemicals thought to possibly have unintended effects on reproductive health. In the U.S., BPA ranks in the top 2 percent of high-production-volume chemicals. BPA is a monomer that makes polycarbonate plastics harder and more resilient. Polycarbonate plas- tics are typically clear and often desig- nated by a “7” within their triangular recycle symbols. BPA is also found in the epoxy resins that line the inside of metallic cans (such as soup and soda cans) and water storage tanks. BPA is also in thousands of other products, including compact discs, eyeglasses, thermal paper, polycarbonate water pipes, medical devices and dental seal- ants. Consumption is thought to be the most common route of human expo- sure because BPA readily leaches from food containers into their contents, especially when its heated, including in a microwave. Centers for Disease Control and Prevention (CDC) scien- tists have estimated that more than 92 percent of Americans have BPA in their
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