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On your next trip to the grocery store, think twice before stocking up on canned goods and gallons of water.

One chemical under scrutiny by Health Canada is bisphenol-A (BPA), a substance used to make polycarbonate plastics -- tough, high-performance plastic material found in the lining of tin cans and used to create reusable, high-performance plastic containers.

It's in our food
According to Sarah Winterton, program director of Environmental Defence, BPA is detected in people who have ingested the chemical through food or liquids stored in plastic containers or plastic-lined cans. "Food is a big marker for bisphenol-A because it slowly leaches out from containers," she says.

Ingesting BPA is a concern because this chemical is classified as an endocrine disruptor -- a substance that interferes with the body's natural hormone system. BPA has estrogenic properties and will bind to the body's estrogen receptors. In short, our bodies think this chemical is the natural hormone and will use it to regulate our entire endocrine system. According to the World Health Organization, endocrine disruptors are linked to decreased sperm quality, early puberty, neurobehavioural problems and cancer.

Exposure is low
Thus said, the amount of BPA we ingest through our food containers is very low. Dr. David Miller, toxicologist and professor of biochemistry at Carleton University, says BPA has been tested extensively for safety and the amount we ingest is well below the safety minimum. "People have been worried about things that bind to estrogen receptors for a long time," he says. "Because of this concern, large testing has gone on in the European Union, the United States, Canada and Japan to get to the bottom of this, to make sure we're not making a big mistake."

He says these different committees from different countries have all come to the same conclusion: that BPA is nothing to worry about when used under conditions of normal use. "To get any effects [from BPA] you would have to melt your bottles down and spoon the stuff in," he says.

However, as of April 2008, Health Canada has announced a reassessment of BPA and is making moves to limit Canadians' exposure to the chemical.

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