Epidemiological study released as FDA re-examines chemical's safety
The first large-scale epidemiological study examining the effects of bisphenol A (BPA) on an adult population has linked the chemical to health problems including heart disease and diabetes.
Details of the research, conducted by David Melzer from the UK’s Exeter Peninsula Medical School and colleagues, were released as the US Food and Drug Administration (FDA)’s science board prepared to discuss BPA’s safety on 16 September.
The researchers found that in 1400 adults aged 18-74, higher concentrations of BPA in urine correlated with reported diagnoses of cardiovascular disease, diabetes, and with clinically abnormal levels of certain liver enzymes. Data came from the 2003-04 US National Health and Nutrition Examination Survey (NHANES).
’We have got a snapshot of one particular moment in time, relating BPA urinary concentration to a range of health problems,’ explains study co-author Tamara Galloway. But it’s not yet clear whether BPA levels are responsible for the health problems. ’These findings could be a reflection of the disease changing the metabolism of BPA, or the reflection of some other unrelated behaviour,’ notes Scott Belcher, a University of Cincinnati pharmacologist. ’We know from animal tests that oestrogenic chemicals like BPA will cause increased body weight - it isn’t unreasonable to think that the same thing would happen in humans.’ Further studies will be need to clarify such questions, the researchers say - including repeating observations over a long period of time, replicating findings in another population, and re-examining routes of exposure to BPA, which is widely used in food and drink container linings, and in polycarbonate plastics in many consumer products.
But other experts say that the research is already very convincing. ’This is serious evidence of harm in people in exactly the areas predicted by the animal research,’ states Wade Welshons, a University of Missouri endocrinologist. ’What would be considered "proof of cause" can’t really be done in people,’ he adds. Getting humans to take defined levels of BPA is not viable for ethical reasons, and it’s nearly impossible to find people who have not been exposed to any BPA for use as controls.
From animals to humans
Animal studies have long suggested that low-level chronic exposure to BPA can lead to reproductive and developmental problems, such as breast and prostate cancers, as well as the early onset of puberty. A report from the National Institutes of Health found ’some concern’ about the effects of BPA on foetuses and children. But the FDA says it has not been proven that typical human exposures pose a safety risk. And in July the European Food Safety Authority (EFSA) concluded that the chemical appears safe at current dosages since humans metabolise and eliminate it more rapidly than do the rats used in scientific research.
Although it is complicated to work out a ’safe’ level of BPA exposure, Galloway says her paper raises doubt about whether the current guidelines set by US and European governments are adequately protective. ’We are seeing the effect of concentrations lower than the level currently recommended by the US Environmental Protection Agency (EPA),’ she told Chemistry World. The EPA’s safety limit is 50 micrograms/kg bodyweight per day, which is also the tolerable daily intake according to the EFSA.
Call to action
Meanwhile, vocal opponents of BPA are suggesting that the new findings should spur regulatory agencies in the US and elsewhere to follow the recent action taken by their Canadian counterparts to declare BPA a ’toxic chemical’ and take steps to curb human and environmental exposures.
’The FDA and the EFSA have chosen to ignore warnings from expert panels and other government agencies, and have continued to declare BPA ’safe’," write University of Missouri reproductive biologist Frederick vom Saal and John Peterson Myers, CEO and chief scientist at the US nonprofit organisation Environmental Health Sciences, in an editorial accompanying the study published in the Journal of the American Medical Association. Other researchers in the field agree with vom Saal and Myers’ view that the apparent inaction of the EFSA and FDA stems partly from efforts from the chemical industry to protect BPA, much as the lead, vinyl and tobacco industries attempted to protect their products.
At the 16 September FDA meeting, a subcommittee of the agency’s science board convened to further consider the agency’s draft assessment of BPA’s safety in food contact applications. The full FDA science board will take delivery of its subcommittee’s views at the end of October. It can then make recommendations to the FDA which may decide on further action, but no timetable has been set for this process.
Scientists sceptical of the FDA review claim chemical lobbyists are behind the effort. They say very little direct review of the actual science will take place, and the agency’s true intent is to issue an FDA statement supporting BPA before a new administration takes over in January.
The American Chemistry Council (ACC), a trade group representing nearly 150 North American chemical manufacturers, continues to vigorously defend BPA. ’Overall, due to inherent limitations in study design, this new study cannot support a conclusion that bisphenol A cuases any disease,’ states ACC’s Steven Hentges. ’The weight of scientific evidence continues to support the conclusion of governments worldwide that bisphenol A is not a significant health concern at the trace levels present in some consumer products.’
The issue has significant implications for industry. Worldwide BPA production has reached nearly 7 billion pounds per year, and its global market is estimated at $6 billion (?3.4 billion).
Updated 17 September, following FDA meeting
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et alJAMA300(11), 1303