What with killer spinach and poisoned Chinese toothpaste and dog food, the risks of environmental chemicals have faded into the background lately. But one group of scientists convened by the government thinks that's a mistake, at least when it comes to  a chemical called bisphenol-A. A building block of certain plastics, it is produced in massive amounts (6 billion pounds per year), and is used in the linings of some food cans, in certain plastic water bottles, baby bottles and other products. Traces of bisphenol-A are found in rivers, oceans and wildlife, in many foods, and in our blood.

Figuring it might be a good idea to know what exactly we're dealing with, given bisphenol-A's ubiquity, the National Institute of Environmental Health Sciences (part of the National Institutes of Health) convened 38 experts from around the world to assess the risks of the chemical. (This was the first time NIEHS has undertaken such a comprehensive review of the potential harm from an environmental contaminant.) The result falls somewhat short of reassuring. After examining over 700 published studies, the scientists concluded that the average level of the chemical in Americans’ blood is very high, far above levels associated with adverse effects in rats and mice, and also well above the government's "safe" level. The trouble with having so much of the chemical sloshing around us is that bisphenol-A acts like estrogen, even minuscule amounts of which can have powerful physiological effects.

Just as you'd expect from a hormone-like compound, very low doses of bisphenol-A can adversely affect the reproductive, nervous, endocrine and immune systems in rodents, especially when exposure occurs during fetal development and infancy. For example, in a study just published in Reproductive Toxicology (where the NIEHS panel's report is also published), the female offspring of rats exposed to bisphenol-A shortly before they gave birth developed uterine fibroids, ovarian cysts, and changes in the uterine lining analogous to endometriosis.

What about people?