From Science Daily:
A new study from Harvard School of Public Health (HSPH) researchers found that participants who drank for a week from polycarbonate bottles -- the popular, hard-plastic drinking bottles and baby bottles -- showed a two-thirds increase in their urine of the chemical bisphenol A (BPA). . . .
The study . . . suggests that drinking containers made with BPA release the chemical into the liquid that people drink in sufficient amounts to increase the level of BPA excreted in human urine.
In addition to polycarbonate bottles, which are refillable and a popular container among students, campers and others and are also used as baby bottles, BPA is also found in dentistry composites and sealants and in the lining of aluminum food and beverage cans. (In bottles, polycarbonate can be identified by the recycling number 7.)