Materials News

BPA studies inconclusive?

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In the first study, a total of 3,423 adults aged 40 years or older (1,087 with type 2 diabetes) were enrolled in the study from May 2008 to August 2009. BPA urinary concentration were measured and the investigators found that the findings did not conform to a previously reported association between urinary BPA levels and self-reported type 2 diabetes.

While several studies have indicated that BPA can be an endocrine disrupter, UK doctors conducted a study (published in the Journal of American Medical Association) three years ago that had found even at doses much lower than the US-based Environmental Protection Agency' (EPA)'s lowest observed level of adverse effects, BPA induces insulin resistance. But the diagnoses of diabetes used in that study were self-reported and also combined with borderline cases of diabetes into a single group. In the Chinese study, participants were given 75 g of oral glucose tolerance test for diabetes. BPA has a fast metabolic rate, with a half-life less than 6 hours after oral administration, and urine is considered the body fluid most appropriate for assessment of BPA exposure.

But the Chinese research did have limitations. Many patients in the study already had diabetes, successful treatment of which could have obscured apparent associations. Dietary variables were not measured; however, this is necessary in observational studies of BPA and diabetes because the presence of the chemical in the body may reflect consumption of sugared drinks in plastic bottles.

Meanwhile as for the Swedish study, it was based on an oral exposure scenario of 200 mg/day and a body weight of 7 kg for a toddler. Furthermore, inhalation of dust in very small children was unlikely as calculations had been made for oral intake of dust via licking from hands.

The Swedish study assumes a comparably high amount of dust and a low-weight child and is therefore a conservative assumption. Nevertheless, taking the measurements from all the 12 samples the average level of BPA measured is 3.08 mg/kg dust (3.08 ppm), resulting in an actual intake at least 570 times beneath the tolerable daily intake limit.

However Belgium-based Plastics Europe, concluded that "for consumers - even for infants and small children - there is no risk from contact with BPA-based products." Furthermore, a recent EPA-funded study also found that human exposure to BPA is extremely low. It also said that BPA is efficiently metabolised and rapidly excreted in urine, making it unlikely that BPA could cause health effects.