After a spate of health concerns in recent years, polycarbonate bottles, the hard-plastic bottles popular among outdoor enthusiasts and parents of newborns, are under scrutiny once again.
A study from HSPH has found that participants’ urinary concentrations of the chemical bisphenol A (BPA) increased by a statistically significant amount after drinking from polycarbonate bottles. BPA is known to disrupt bodily responses to endocrine hormones, and exposure to BPA has been linked to altered sexual maturation in mice and chronic heart disease and diabetes in humans.
Led by first author Jenny Carwile, a doctoral student in the Department of Epidemiology, the researchers recruited 77 Harvard College students to participate in the study. For a week in April 2008, the subjects were told to drink all cold beverages from a polycarbonate water bottle. At the end of the week, their urine was collected to measure BPA levels. The researchers also measured BPA in a urine sample taken the week before, during which the students were instructed to drink from a stainless steel bottle in order to reduce any existing BPA levels in their bodies.
Comparing the two urine samples, the researchers found that participants’ urinary BPA concentrations increased by 69 percent after drinking from the polycarbonate bottles for one week. This difference was even more pronounced (77 percent) when the results were restricted to participants who reported greater than 90 percent compliance, compared to 55 percent for a lower-compliance group. The difference between the two groups, however, was not statistically significant.
“Past experiments have only looked for chemicals in the contents of polycarbonate bottles,” said Karin Michels, senior author of the study and associate professor in the Department of Epidemiology at HSPH. “This study is the first to expose actual people to the bottles. By changing just one factor—that is, drinking from these very popular hard-plastic bottles—and no other sources, urinary BPA increased by two thirds. We did not expect such a dramatic change.”
The authors noted that participants drank only cold beverages from the bottles, to mimic conditions of normal use. “If we had asked them to put hot liquids in there, the effect would have been bigger,” said Michels. “This is, in fact, what happens with baby bottles.”
Since its publication online May 21 in the journal Environmental Health Perspectives, the study has touched off a debate about the safety of BPA in places as far away as Denmark and Germany. Some countries, such as Canada, have banned the chemical from baby bottles outright. “This study is coming at an important time because many states are deciding whether to ban the use of BPA in baby bottles and sippy cups,” said Carwile.
“I think this has increased awareness that BPA is measurable and can get into your body,” said Michels. “People realize it is real, and more serious.”
Students may contact Karin Michels at firstname.lastname@example.org for more information.
Conflict Disclosure: The authors declare no conflicts of interest.
Funding Sources: Harvard University Center for the Environment faculty research grant; National Institute of Environmental Health Sciences Biological Analysis Core through the Department of Environmental Health, Harvard School of Public Health; Training Program in Environmental Epidemiology under grant T32 ES07069; the content of the work is the responsibility solely of the authors.