David Biello in Scientific American:
Bisphenol A (BPA) is a ubiquitous compound in plastics. First synthesized in 1891, the chemical has become a key building block of plastics from polycarbonate to polyester; in the U.S. alone more than 2.3 billion pounds (1.04 million metric tons) of the stuff is manufactured annually.
Since at least 1936 it has been known that BPA mimics estrogens, binding to the same receptors throughout the human body as natural female hormones. And tests have shown that the chemical can promote human breast cancer cell growth as well as decrease sperm count in rats, among other effects. These findings have raised questions about the potential health risks of BPA, especially in the wake of hosts of studies showing that it leaches from plastics and resins when they are exposed to hard use or high temperatures (as in microwaves or dishwashers).
The U.S. Centers for Disease Control (CDC) found traces of BPA in nearly all of the urine samples it collected in 2004 as part of an effort to gauge the prevalence of various chemicals in the human body.