Polycarbonate plastic is durable, impact-resistant, and clear, making it an ideal material for baby bottles, refillable water bottles, sippy cups, and many other food and beverage containers. It is also found in eyeglass lenses, compact discs, dental sealants, and plastic dinnerware, and as a resin, it forms the protective lining for metal food and beverage cans.
But recent research has raised concerns over the health effects of a chemical used in the manufacture of polycarbonate bisphenol A (BPA). Some studies have found that BPA can leach in trace amounts from polycarbonate containers and resin linings into foods and beverages. In tests on laboratory animals, BPA appears to mimic or disrupt the hormone estrogen and thus affect the reproductive system, possibly raising the risk for cancer.
Infants and young children are at greatest risk because they eat and drink more than adults on a pound-for-pound basis, and so have greater exposure to BPA, says the National Institute of Environmental Health Sciences (NIEHS). Because of this risk, Canadian health officials have proposed banning the sale of polycarbonate baby bottles beginning in June 2008 and may require that infant formula containers use some other lining than polycarbonate resin. Canada has also begun monitoring BPA exposure in 5,000 adults to see what long-term effects the chemical may have.
A popular plastic
Polycarbonate plastic is found virtually everywhere in modern life, and BPA is one of the highest-volume chemicals produced worldwide. Polycarbonate plastic has proved a versatile alternative to glass and ceramic containers, which break or can be difficult to clean. Polycarbonate plastic bottles can be sterilized easily and don't absorb odors. As a resin, polycarbonate lines the insides of most canned foods, including baby formula.
Other types of plastics are also used as food and beverage containers. You can tell one plastic from another by the recycling triangle stamped on the container (usually on the bottom). Polycarbonate containers carry a No. 7. Here's a rundown from the American Chemistry Council on the major plastics:
1 - PET (polyethylene terephthalate); used for water, juice, sports drinks, soft drinks, beer, mouthwash, peanut butter, pickles, food trays for the microwave
2 - HDPE (high density polyethylene); used for milk, water, juice, cosmetics, shampoo, laundry detergent, bags for groceries, cereal box liners
3 - PVC (polyvinyl chloride); used for clamshell takeout containers, wrap for deli foods
4 - LDPE (low density polyethylene); bags for bread, frozen foods, and produce; coating for paper milk cartons and hot/cold beverage cups; squeezable honey and mustard bottles
5 - PP (polypropylene); used for containers for yogurt, margarine, takeout foods; bottle caps for ketchup and syrup
6 - PS (polystyrene); used for clamshell takeout containers; meat and poultry trays; plastic cups, plates, and bowls
7 - Other (includes polycarbonate); used for 3- and 5-gallon reusable water bottles; baby bottles; bottles for citrus juices and ketchup; oven-baking bags
What's the problem?
In a 2003-04 health survey, the Centers for Disease Control and Prevention (CDC) made a surprising discovery: It found BPA in the urine of nearly 93 percent of the more than 2,500 people tested. The survey evaluated children 6 years old and older, teens, and adults. Females had significantly higher levels of BPA than did males, and children had the highest levels.
Most people are exposed to BPA through foods and beverages, the NIEHS says, although it's also found in air, dust, and ground and surface water. A typical adult takes in daily about 1 microgram (mcg) of BPA for every 2.2 pounds of body weight. Infants who are fed with polycarbonate bottles and canned formula may take in 10 mcg for each 2.2 pounds of weight. A 15-pound infant, for instance, would consume about 68 mcg of BPA a day, the same amount as a 150-pound adult.
BPA ends up in foods and beverages because it leaches from containers and can linings. Certain foods and heat appear to speed up the leaching, the NIEHS says.