An influential new study linking bisphenol A to heart disease and diabetes is raising the possibility that Health Canada erred in April when it concluded that the chemical used to make plastic poses no risk to adults.
The new research, the largest investigation to date on the chemical's possible effects in humans, found that those with higher exposures to bisphenol A had 2.9 times the odds of having cardiovascular disease and 2.4 times the odds of having adult-onset diabetes, compared with those with lower exposures. Those with more of the chemical also had liver enzyme abnormalities.
The study, issued Tuesday in the Journal of the American Medical Association, was based on the typical ranges of bisphenol A found in American adults.
Health Canada made regulatory history in April by proposing to place bisphenol A on the government's list of toxic substances and banning it from baby bottles. That made Canada the first country in the world to recommend such actions against the ubiquitous compound used in everything from polycarbonate plastic office water-cooler jugs to the resin linings inside nearly all tin and pop cans.
Health Canada took the action based on worries that newborns and infants might be overexposed to the chemical. But Health Minister Tony Clement assured at the time that "most Canadians need not be concerned … because health effects occur at levels much greater than those we are exposed to in Canada."
The new finding "throws out the window" the idea that BPA "poses no risk to the adult," said Dr. Frederick vom Saal, a biologist at the University of Missouri who is an expert on the chemical. "We have a very high level of confidence that at human-exposure levels, bisphenol A is causing disease."
Health Canada did not respond to requests for comment.
The Conservative government has touted the BPA proposal as one of its major accomplishments. Environmentalists, while applauding the toxic-listing idea, say the new research indicates the chemical should be removed from food and beverage packaging, particularly tin cans, considered a major exposure source.
"The implications of this further study are obvious," said Rick Smith, executive director of Environmental Defence, an activist group. "The government needs to look at protecting the adults, not just infants."
The department must issue its final decision on declaring BPA toxic by Oct. 18, just after the federal election.
The JAMA study was released to coincide with a hearing at the U.S. Food and Drug Administration on BPA. The FDA issued a draft assessment in August concluding BPA usage is safe.
In the new study, the authors - academics based in Britain and the United States - were cautious, writing that their research on its own doesn't establish conclusively that BPA causes diabetes or heart disease. But they say it adds to laboratory testing on animals that has found the chemical can cause harm.
"Independent replication and follow-up studies are needed to confirm these findings and to provide evidence on whether the associations are causal," the paper concluded. "Given the substantial negative effects on adult health that may be associated with increased BPA concentrations and also given the potential for reducing human exposure, our findings deserve scientific follow-up."
The new research follows a spate of recent scientific papers that have raised concerns about BPA, which has a molecular shape that fools cells into thinking it is estrogen, leading to worries that exposures are giving people an extra dollop of the female hormone.
The amounts leaching from tin cans or polycarbonate plastic bottles are tiny - only a few parts per billion - but this is still about a thousand times higher than natural concentrations of estrogen in people.