Teenagers may carry the highest levels of bisphenol A - about 30 per cent more than the rest of the population, according to the first national survey about the compound conducted by Statistics Canada, but exposure to the estrogen-mimicking chemical is widespread, with detectible levels in 91 per cent of Canadians.
The survey, released Monday, found that the average level of BPA, as the substance is known, was just over one part per billion, an exceedingly small amount, but still a thousand times higher than natural levels of estrogen found in the body.
Statistics Canada said its data, based on urine samples collected from more than 5,400 people aged six to 79, suggest there is "continual widespread exposure in the Canadian population" to BPA. The Statscan sampling is the largest such effort done to date in the world.
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"Although BPA may constitute a health risk, no guidance values are currently available in Canada for urinary BPA," the federal agency said of its findings.
The everyday chemical is used to produce everything from CDs to the liners of nearly all tin cans, and has emerged as one of the most debated substances in use because of concerns that exposures amount to receiving an extra dose of estrogen.
Two years ago, Canada was the first country in the world to propose declaring it a toxic substance, although it has yet to do so. Both the U.S. Environmental Protection Agency and the Food and Drug Administration have announced that they are conducting safety of the chemical.
Some scientists and public-health advocates are worried about even these trace amounts, saying they could contribute to increased risk of breast cancer and precocious puberty in girls, among other hormonally caused health impacts that have been observed in animal experiments using low-level exposures to the compound.
Health Canada said it wasn't surprised by the findings because the results are in line with research from other advanced countries showing nearly everyone has some BPA.
As for possible health concerns, it said its scientists are conducting research "related to the potential effects of low concentrations of BPA on human health."
Food is considered the major source of BPA. Teenagers had the highest average amounts, possibly because they eat more food relative to their body size or have metabolic differences.
Monday's survey has led to calls to further regulate BPA.
"The No. 1 priority at the moment has got to be getting it out of the lining of tin cans," said Rick Smith, executive director of Environmental Defence, an advocacy group.
"When nine out of 10 Canadians have a hormonally active chemical in their body, for which easy alternatives are available … why not make some further changes with respect to BPA?"
The trade association representing companies making BPA said the Statscan findings show that Canadians shouldn't be worried about any possible health hazards.
The new data on consumer exposure to BPA in Canada "is very reassuring and confirms that people are exposed to only minute levels that are eliminated from the body," said Steven Hentges, a spokesman for the American Chemistry Council.
When people ingest BPA through food, about half is broken down in the digestive track into a harmless compound that doesn't have estrogenic activity every six hours or so.
The fact that most people have the chemical in their urine suggests they were having regular exposures in the 24 hours to 36 hours before their tests, says Frederick vom Saal, a biologist at the University of Missouri and a leading U.S. researcher on BPA.
Dr. vom Saal said he found it "really concerning" that younger people had higher levels than those who are older because exposure to hormones during key points in childhood development can cause permanent, lifetime changes in the way cells are organized and operate.
But the view that BPA represents a threat is disputed.
"The presence of a substance doesn't mean anything other than that it's there. It doesn't mean that it causes any harm," said Joe Schwarcz, director of McGill University's Office for Science and Society.
Dr. Schwarcz says the bio-monitoring data would need to be follow up by decades of surveillance to find out whether health outcomes varied by exposure to the chemical.Report Typo/Error