Lacing food with an estrogen mimic.

Bisphenol A, a building block of polycarbonate plastics, can mimic the effects of the body's natural estrogens (SN: 7/3/93, p. 12). In tests meant to simulate the use and cleaning of plastic food ware, a Food and Drug Administration study now shows that bisphenol A (BPA) can leach into liquids.

This raises public health concerns because a variety of estrogen mimics can alter the development of animals (SN: 1/8/94, p. 24)--and perhaps people (SN: 1/22/94, p. 56).

Polycarbonates are made by joining BPA molecules into long chains. Not every molecule gets linked, however, leaving some BPA free to migrate from the finished product. John E. Biles and his coworkers at FDA in Washington, D.C., found that polycarbonate baby bottles and juice cups contained from 7.4 to 46.7 micrograms of unbound BPA per gram of plastic.

Heating tests that simulated stove-top sterilization triggered the bottles to release 5 percent of the unbound BPA into a mixture of alcohol and water designed to mimic the baby formula and fatty foods that might be stored in polycarbonate containers. Repeated treatments released smaller amounts. In exaggerated conditions--where the plastic was bathed at a lower temperature, about 150 [degrees] F, for 10 days in a solution of 50 percent alcohol in water--"migration as high as 368 percent of the original residue level of BPA [31.5 micrograms per gram of plastic] ... was observed," FDA chemists report in the September Journal of Agricultural and Food Chemistry. The latter, very high numbers "strongly suggest there is hydrolysis," a breakdown of some of the plastic, freeing up more BPA, says Biles.

In a less extreme experiment, distilled water was held in large polycarbonate containers for 39 weeks at room temperature. Some BPA migrated, eventually contaminating the water at concentrations of almost 5 parts per billion.

Though others have observed qualitatively that BPA can leach from plastic, "these numbers are more quantitative than what had been reported," says Ana Soto of Tufts University School of Medicine in Boston. "This demonstrates that we can measure BPA and should, to determine how much people--especially children--can be exposed to [in foods]."