In her paper - Exposure to bisphenol A in Canada: invoking the precautionary principle - Laura Vandenberg, of Tufts University Massachusetts, also examines possible causes behind findings that BPA exposure is higher in the US than Canada. She speculated that the absence of BPA plants in Canada – and the resulting lowering of environmental exposure – could account for this difference.
BPA is a substance commonly used in the manufacture of polycarbonate baby bottles and the epoxy linings of food and beverage cans. Annual global output is thought to exceed three million tonnes. Strong concerns have been voiced from some quarters over its estrogenic properties and the effects of the chemical on the human reproductive system. But regulatory agencies in Europe and the US continue to maintain it is safe at current exposure levels in food packaging
Risk of confusion
Vandenberg observes that Health Canada has taken up a “unique position” in labelling the chemical as toxic but questions why no stronger measures have been taken to ban the chemical.
"Health Canada continues to maintain that bisphenol A is safe at current exposure levels and does not pose any risk to the general population; regulations to remove bisphenol A from all food-contact sources, or ban it completely, are not yet forthcoming, presenting a conflict that is likely to confuse the public,” said Vandenberg in an article in the Canadian Medical Association Journal (CMAJ).
The agency has stated that “the potential harmful effects of bisphenol A during development cannot be dismissed and that the application of precaution is warranted”, she said.
"By invoking the precautionary principle, Health Canada has both the power and responsibility to restrict human exposure to BPA; in taking the action to label BPA a toxic chemical, Health Canada now must follow through with strong legislation that will protect the people of Canada from continued exposure," Vandenberg said.
The paper also quotes a recent large-scale study of 5,476 Canadians that reported almost 90.7 per cent had detectable levels of BPA, against 92.6 per cent the US population – with highest urine concentrations among children and adolescents. However, she said concentration of BPA in Canadians was far less than of their US counterparts across all age ranges.
"The comparison between concentrations measured in Canada and US populations are particularly interesting because these two populations are often thought to be demographically similar," said Vandenberg. "Surprisingly, for each age group that was analysed, the concentrations found in Canadians were approximately half those found in Americans."
While highlighting food packaging and thermal receipt papers as a potential source, she said that environmental sources “may be key to understanding the differences between urine concentrations seen in the US and Canada”.
In 2008, no bisphenol A was produced in Canada, whereas almost 1 million tonnes of it were manufactured in the US, added the researcher.
“Thus the environmental contamination that results from the production of BPA in the US may contribute to the higher levels seen in that population," said Vandenberg.
Exposure to bisphenol A in Canada: invoking the precautionary principle by Laura Vandenberg is published in the Canadian Medical Association Journal; DOI:10.1503/cmaj.101408