By now most Canadians are familiar with bisphenol A or BPA, a chemical still widely used in food containers that many worry might present a health risk.

Several studies have noted that BPA can mimic the hormone estrogen and have linked it to a number of health problems, from cancer, to obesity and even diabetes.

The concerns about BPA compelled Canada and several other countries to ban its use in baby bottles. That ban has led to a new market for BPA-free plastic bottles.

But what do we know about the replacement chemicals that are used in BPA-free plastics?

A number of studies suggest many BPA-free plastics substitutes may be no better than BPA.

One study found that 95 per cent of plastic products sold as BPA-free still leeched chemicals that mimicked estrogen, just as BPA does. 

Those studies worry Prof. Chris Metcalfe, a professor of environmental and resource studies at Trent University in Peterborough, Ont.

"The message to consumers is that BPA-free does not necessarily mean that the plastic doesn't have estrogenic activity," he tells CTV News.

One of the more popular BPA replacements appears to be a chemical called bisphenol sulfonate, or BPS.  Recent studies have found BPS in plastic bottles and the lining of food cans, even in cash register receipts, tickets and flyers.

A study by New York State’s public health department found that BPS was found in more than 80 per cent of human urine samples collected from various countries.

“It means it is widespread,” Dr. Kurunthachalam Kannan, head of the health department’s organic chemistry lab, told CTV.

Kannan raised concern that while itis widely used, very little is known about BPS and its effect on the environment.

He said consumers should be warned of all bisphenol chemicals that are found in products, not just BPA.

“Some manufacturers have already reported that they are replacing BPA with BPS,” he said.

“They are structurally very similar.”

Some studies suggest BPS has similar estrogen-like effects as BPA, yet is less biodegradable. 

"With bisphenol S, there are suggestions that it lasts longer in the body and isn't metabolized as quickly as BPA," says Metcalfe. "We need more study in order to make an informed decision."

Environmentalists say it could take years for scientists to understand the risks of these replacement plastics - even as consumers rush to buy these so-called less toxic bottles.

Rick Smith, the executive director of Environmental Defence, says the problem is that there's nothing that compels chemical companies from proving their chemicals are safe before they hit the market.

"As manufacturers move to complicated new chemicals, our current legal system doesn't require them to demonstrate those chemicals are safe prior to including them in their products," Smith says.

The chemical agencies CTV News contacted declined comment about the concerns.

Environmental experts say instead of focusing on just BPA-free products and one "suspect" chemical, scientists may need to look at the whole array of plastics that come in contact with our foods and drinks.

Since it's not possible to know the full risks of these chemicals, environmental groups advise consumers who don't want to wait for studies to be completed, to use glass, ceramics or stainless steel containers instead.

"People cannot be expected to be chemical engineers when they shop for their kids or for their home," says Smith.

With a report from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip