A Health Canada study of canned pop has found the vast majority of the drinks contain the chemical bisphenol A, a substance that imitates the female hormone estrogen and is banned in baby bottles.

Out of 72 drinks tested, 69 were found to contain BPA at levels below what Health Canada says is the safe upper limit. However, studies in peer-reviewed science journals have indicated that even at very low doses, BPA can increase breast and ovarian cancer cell growth and the growth of some prostate cancer cells in animals.

"There is no risk to Canadians," Health Canada spokesman Stéphane Shank told CBC News. "The average adult weighing approximately 60 kilograms would have to consume over 900 cans per day" to reach the department's safety threshold, he said.

The canned pop Health Canada scientists tested all came from stores in Ottawa in April 2007 and included diet, non-diet, fruit-flavoured and energy drinks. These drinks represent at least 84 per cent of the market share of soft drinks sold in the country.

The federal department's study was published in January in the Journal of Agricultural and Food Chemistry and was posted on Health Canada's website. When asked why the study was not widely publicized, Shank said "it wasn't our intent" to hide it.

The study did not find detectable levels of BPA in two types of tonic water, likely the result of a bittering agent used in tonic drinks that could interfere with BPA extraction. It also found no traceable levels in one energy drink, but did not suggest why that might be.

'Significant biological effects'

Bisphenol A is a chemical compound found in some hard, clear, lightweight plastics and resins. The materials are used in the production of various types of food and drink containers, compact discs, electronics and automobile parts, and to line some metal cans, including pop cans.

While Health Canada's position is that there is no health risk in drinking canned pop because the levels of BPA are so far below the safe threshold, critics say BPA — like estrogen — is active in very small amounts.

"The chemical is known to cause significant biological effects at incredibly low levels," Rick Smith, executive director of Environmental Defence, told CBC News. "And this is not the only source of this chemical in our daily lives. If it was the only source, Health Canada might have a leg to stand on."

The beverage industry, on the other hand, questions whether BPA has the impact some studies say it has. "It's asserted this is an estrogen mimicker," Justin Sherwood, president of Refreshments Canada, told CBC News. "We as an industry take our cue from Health Canada."

In October 2008, Canada became the first country in the world to ban the import and sale of polycarbonate baby bottles containing bisphenol A. The federal government also announced it would devote $1.7 million over three years to study the chemical.

Health Canada's ongoing evaluation of bisphenol A has included a review of human and animal studies around the world, in addition to research into how much of the chemical is leaching from consumer products. The research is part of a more comprehensive review of about 200 chemicals the federal government has singled out for more careful study.