Plastic baby bottles are easier for both you and your baby to hold and don't pose a risk of broken glass if your baby flings it to the floor. But chemicals used to harden polycarbonate in some older baby bottles could harm your baby. While most manufacturers no longer use the chemical Bisphenol A, or BPA, to make baby bottles, older bottles and sippy cups might still contain the chemical and should not be used.
Identifying BPA Sources
Bottles manufactured in the United States are marked with numbers on the bottom that are used for recycling purposes. Clear plastic baby bottles made with BPA will be marked on the bottom with a number 7, the category for "other" plastics, or with the letters "PC," which stands for polycarbonate. Not all plastics marked with the number 7 contain BPA; category 7 includes all plastics made from combinations of other plastics in categories 1 through 6 as well. Manufacturers also use BPA in a number of canned food container linings, including infant formulas.
The risks of ingesting BPA for infants haven't been well-studied in humans -- most evidence comes from animal studies. This chemical might have estrogenic effects that could cause early puberty or behavioral changes in children. A Harvard School of Public Health study published in the November 2011 issue of "Pediatrics" tested the effects of BPA exposure in children during gestation and up to 3 years of age. Researchers found that girls, but not boys, exposed to higher concentrations of BPA during pregnancy had more anxious or depressed behavior and poorer emotional control and inhibition at age 3. No effect was found from childhood exposure.
Heating plastic in the microwave causes the plastic to break down, which allows chemicals such as BPA to leach into the food. Heating on the stovetop in boiling water can also break down the plastic; warm bottles instead by placing them in warm water. When you warm bottles in the microwave, you can also get uneven warming, meaning that some areas could be much hotter than others. Washing and drying plastic bottles in the dishwasher can also break plastic. Hand-wash bottles in warm, soapy water to reduce breakdown and chemical leaching. Don't heat plastic liners in boiling water or in the microwave either. Although they don't contain BPA, the chemicals they do contain can also break down and enter the formula with heating.
All major manufacturers of plastic baby bottles in the United States voluntarily removed BPA from their baby bottles when BPA became a health concern in 2008. The Food and Drug Administration banned the use of BPA in baby bottles in 2012. Opaque bottles, marked with a number 2 or 5, contain polyethylene or polypropylene rather than BPA, the American Academy of Pediatrics explains.