New research from the US suggests that people who drink from bottles made of polycarbonate plastic, such as that used to make hard-plastic drinking bottles and baby bottles, have a considerably higher level of the chemical bisphenol A (BPA) in their bodies compared to when they do not.

The finding confirms concerns expressed by consumer groups and public health experts, that polycarbonate plastic bottles are an important source of the BPA that finds its way into the human body. BPA has been shown to interfere with reproductive development in animals, and has been linked to cardivascular disease and diabetes in humans, among other things.

The study was the work of senior investigator Karin B Michels, associate professor of epidemiology atHarvard School of Public Health (HSPH) and colleagues, and was published online in the May 12 issue of Environmental Health Perspectives.

Michels and colleagues found that participants who drank for a week from from polycarbonate bottles showed a two-thirds increase of BPA in their urine.

Other studies have shown that BPA can leach from the container into the liquid, but this is the frist to show a corresponding increase of BPA in urine in humans.

Hard plastic polycarbonate bottles are often used as refillable containers by students, campers and others (for instance people in gyms refill them from the water fountains). They are also used as baby bottles, although two months ago 6 manufacturers in the US said they would stop selling hard plastic baby bottles made with BPA.

If a hard plastic bottle carries the recycling symbol showing the number 7, then it is most likely made of polycarbonate, since 7 is the category for "all other plastics", which includes polycarbonate (according to the SPI resin identification coding system).

BPA is also found in dentistry composites and sealants and in the lining of aluminum food and beverage cans.

Several studies have shown that BPA disrupts hormones in animals, leading to early sexual maturity, changes in development and organization of tissue in mammary glands and reduction in sperm in the affected organism's offspring. The early stages of fetal development are thought to be the most vulnerable to harm from BPA, said the authors in a prepared statement.

Michels said that:

"We found that drinking cold liquids from polycarbonate bottles for just one week increased urinary BPA levels by more than two-thirds."

"If you heat those bottles, as is the case with baby bottles, we would expect the levels to be considerably higher," she added, explaining that is worrying because "infants may be particularly susceptible to BPA's endocrine-disrupting potential".

For the study, Michels and colleagues recruited 77 Harvard College students in April 2008. For the first week the participants went through a "wash out phase" where they only drank cold drinks from stainless steel bottles to purge their bodies of any lingering BPA.

They were then each given two polycarbonate bottles and asked to use them and no other bottles for storing the cold drinks they drank for the following week.

The participants gave urine samples at the end of the wash out week and the week they used the polycarbonate bottles.

The results showed that their urine contained 69 per cent more BPA at the end of the polycarbonate week than at the end of the wash out week.

The authors wrote that the participants' BPA levels were similar to those reported for the population at large.

The students drank from the polycarbonate bottles in a "normal use setting", wrote the authors, and they did not wash them out in dishwashers or use hot water or hot liquids in them. This means the BPA levels might have been even higher if the participants had drunk hot liquids out of them, since heat increases the amount of BPA that leaches into the liquid (one of the reasons for the heightened concern around baby bottles).

Canada banned the use of BPA in polycarbonate baby bottles last year.

The authors called for more research to look into the effect of BPA on babies, and on reproductive disorders and breast cancer in adults.

If you are concerned about whether the plastic bottles you use were made with BPA, you should contact the manufacturer. For instance we have noticed that some retailers have started saying on their websites that their mineral water is sold in plastic bottles made with PET plastic, or glass, and not polycarbonate.

"Use of Polycarbonate Bottles and Urinary Bisphenol A Concentrations."
Jenny L. Carwile, Henry T. Luu, Laura S. Bassett, Daniel A. Driscoll, Caterina Yuan, Jennifer Y. Chang, Xiaoyun Ye, Antonia M. Calafat, Karin B. Michels.
Environmental Health Perspectives, online May 12, 2009.
doi:10.1289/ehp.0900604

Source: Harvard School of Public Health.

Written by: Catharine Paddock, PhD