People may have longer exposures to common plastic additive.

Mar 01, 2009

Stahlhut, RW, WV Welshons and SH Swan. 2009. Bisphenol A data in NHANES suggest longer than expected half-life, substantial non-food exposure, or both. Environmental Health Perspectives doi:10.1289/ehp.0800376.

Synopsis by Paul Eubig, DVM

Researchers evaluating bisphenol A levels in urine samples conclude that current assumptions about sources and longevity may be incorrect.

Levels of bisphenol A (BPA) measured in people's urine don't add up to support current ideas about exposure to the common chemical in plastics, according to research examining the persistence of the chemical.

To date, researchers thought the main source of BPA in people was food and drink. They also assumed the chemical broke down and was removed from the body quickly, within hours of being consumed.

But a new analysis of measured amounts of BPA in samples from more than 1,400 adults question those long held beliefs. The data were collected as part of a national database by the Centers of Disease Control and Prevention.

Researchers assumed that if the main source of BPA is food and drink, then levels in the body and the urine should decrease the longer the time from the last meal. However, when the scientists compared levels of BPA in urine samples to the time when volunteers last ate or drank, they found that levels did not decrease as quickly as expected.

The unexpected finding led the researchers to propose that people are exposed to BPA from non-food sources between meals or that BPA is not cleared from the body as fast as has been previously estimated, or maybe both.

 If the chemical is spending more time in the body than previously expected, there is greater likelihood for it to cause harm, especially to growing fetuses, infants and children.

Bisphenol A is a chemical commonly used in certain plastics and epoxy resins. Exposure to bisphenol A is widespread and occurs daily because it is released from the lining of food and drink containers. It is also found in carbonless paper for receipts, eyeglass lenses, compact disks, dental resins and polyvinylchloride.

Bisphenol A is of concern because it mimics the hormone estrogen. Animal studies find even very low levels can produce a variety of reproductive and developmental effects on the uterus, testes and brain. Some human studies associate BPA exposure with subtle changes to the reproductive system.

The US, Canada and other countries are considering whether levels of bisphenol A in consumer products should be better regulated. US results are mixed with some agencies finding current standards acceptable while scientific advisory panels find reason for concern. Those in favor of more stringent regulation point to studies that show very low doses of bisphenol A can affect health. Others, who may be more aligned with industry, argue the findings do not accurately reflect human exposure to the chemical.