Plastic baby bottles and other food containers are often made with Bisphenol A (BPA) which has been found to be highly damaging to DNA and at low doses can mimic sex hormones.
Findings of low-dose effects from BPA are controversial not just because they could damage the plastics industry, but because they also call into doubt long-held beliefs about measuring risk from any kind of chemical exposure. Generations of toxicologists have been taught that "the dose makes the poison" that the impact of a chemical will be strongest at high doses and will decrease in proportion to a decrease in dose. Below some threshold level, there should be no biological effects at all. But according to Wade Welshons of the University of Missouri's Columbia College of Veterinary Medicine, such assumptions are wrong when it comes to chemicals that imitate hormones, because the endocrine system is designed to respond to small, subtle changes in hormone concentrations far below doses used in traditional toxicity testing.
Researcher Patricia Hunt at Case Western Reserve University is now studying male mice that were exposed to BPA in the womb or soon after birth. Her preliminary results suggest that the chemical causes genetic mistakes in the formation of sperm, just as it does in eggs. "If I could accomplish one thing from these studies," concludes Hunt, "I'd like to get all those baby bottles and sippy cups made of polycarbonate off the market."
How to identify plastic products containing BPA:
- Plastic containing BPA polymers carries the recycling symbol #7, which can also indicate other kinds of mixed plastics. The plastic may be called polycarbonate, lexan or polysulfone and is generally a clear, hard plastic, although it may be tinted different colors.
- Clear plastic baby bottles and children's training cups are likely to be made of polycarbonate.
- If in doubt, contact the manufacturer to ask if the bottle or cup is polycarbonate.
What you can do to minimize your family's exposure:
- Replace plastic food and beverage containers and kitchen utensils with glass, ceramic or metal where possible.
- Some glass baby bottles are available, though many daycare centers won't allow them for fear of breakage. A less fragile alternative is to use baby bottles and sippy cups made of polyethylene plastic (#1, #2, #4 recycling symbols) or polypropylene (#5). Nonpolycarbonate plastic bottles and cups are usually colored, not clear.
- If you do use polycarbonate containers, don't expose them to heat or harsh detergents. Studies have shown that scratched or worn polycarbonate leaches more BPA, so keep plastic containers away from the microwave and dishwasher and don't clean stained water bottles or other containers with bleach.
- The question of whether enough BPA leaches out of dental sealants to create a health hazard is unresolved. You may want to avoid dental sealants for children's baby teeth.
More information at National Wildlife