Studies show significant links between reuse of plastic water bottles and increased levels of the chemical bisphenol A (BPA), a common component in plastics. In one example, conducted by Harvard School of Public Health, test participants who drank from polycarbonate plastic water bottles had BPA levels nearly 2/3 higher than those who did not, after just one week. BPA levels equivalent to those shown by the test subjects have been known to cause a host of endocrine system related health effects in animals, including "early sexual maturity, changes in development and organization of tissue in mammary glands and reduction in sperm in the affected organism's offspring." Infants were at higher risk than the adults.

On the Other: Data Is Inconclusive

No conclusive studies have directly linked high BPA levels with these negative effects in humans, as most studies rely on results from animal testing at this point. According to the director for Johns Hopkins Bloomberg Center for Water and Health, "Most single-use water bottles sold in the United States are made from BPA-free plastic" anyhow---meaning reuse of many plastic drinking bottles is probably safe.

Bottom Line

While there are no conclusive studies to show direct danger to humans, the research suggests that reuse of plastic water bottles can very adversely affect health---especially in infants.

Source:

MedicalNewsToday.com: BPA Chemical Stufy

JHSPH.edu: Q&A: Bisphenol A and Plastics