American Scientist

To the Editors:

Heather Patisaul’s feature article “Assessing Risks from Bisphenol A,” (January– February) nicely illustrates the difficulties in trying to assess human health effects from low levels of chemicals in our environment. The author would have benefited, however, from collaboration with a materials scientist.

Early on she notes that BPA is a common ingredient in many hard plastics. BPA is a monomer for polycarbonate (66 percent) and epoxy (30 percent). Those polymers constitute only about 3 percent of U.S. plastics production of over 100 billion pounds in 2008. BPA is hardly a common ingredient.

By the end of the article, Patisaul said, “DDT undoubtedly saved lives, and likely still does. No such case can be made for BPA. It is time to develop a clear and comprehensive strategy for assessing the potential public health consequences of endocrine disruptors such as BPA that may contribute only economic value.” To understand the public health consequences and develop a clear strategy, one must understand the materials involved, how they are used and the routes and levels of exposure to compounds of concern. Why are epoxy coatings used for certain cans? They reduce the likelihood of botulism. Someone behind impact- or bullet-resistant windows might value the protection they give.

Technologies exist largely because of the underlying materials. Consider CDs. Polycarbonate is a lightweight, high-impact, heat-resistant, intrinsically flame-retardant plastic. The first three qualities are why BPA was used in baby bottles. If better materials are available, great. But let’s not throw CDs, electrical appliances and bullet-resistant windows out with the baby bottles.

Gordon L. Nelson
Dean, College of Science
Florida Institute of Technology

Dr. Patisaul responds:

Information about BPA production levels comes from the “NTP-CERHR Monograph on the Potential Human Reproductive and Developmental Effects of Bisphenol A,” at http://cerhr.niehs.nih.gov/chemicals/bisphenol/bisphenol.pdf.

As for routes of exposure, you don’t need solvents to get BPA to migrate. As it turns out, you don’t even need heat. A Harvard University research group reported in June that consumption of cold beverages from polycarbonate bottles containing BPA raises human urine levels of BPA by 69 percent.

Exposure to BPA is low but that does not mean it is innocuous. That type of “the dose makes the poison” thinking may not apply to endocrine disruptors because their dose responses appear to be non-monotonic in many cases. Given that, if you don’t need it in food containers, why not pull it out and be on the safe side?