Early this year, a report by a California environmental group brought attention to toxic chemicals in plastic baby bottles, causing a run on glass versions. Next came a conference funded by the National Institutes of Health and other major groups at which similar warnings were announced. The concern: A chemical in some plastics called bisphenol A (BPA)  -- which has been linked with cancer, impaired immune function, hyperactivity, and other problems  -- can leach into a bottle's contents.

"There's no need to be frightened, but you should try to reduce your baby's exposure to this chemical," says pediatrician Harvey Karp, M.D., a board member of Healthy Child Healthy World, a non-profit group that raises awareness about environmental toxins. Here's how:

Avoid hard polycarbonate plastic, which contains BPA. Instead, use bottles made of glass, or softer, safer plastics made of polyethylene, polypropylene, or polyamide. Brands that carry these include Born Free (which makes only BPA-free bottles), Gerber, Sassy, and Medela; call the manufacturer to check which it sells.

Discard worn bottles (those that are cloudy or scratched): Chemicals leach into food more easily when plastics break down.

Don't heat plastic bottles in the microwave, or wash them in the dishwasher, since heat degrades plastic, releasing chemicals.