Testing in the U.S. is raising concerns that environmentally friendly reusable shopping bags could actually contain lead. But are all bags created equal?

A newspaper in Florida has found that Chinese-made grocery bags from two major chains contained the toxic chemical, in some cases exceeding the levels set by government.

Angela Duso, a chemistry instructor at BCIT, says that the relative safety of grocery bags can be complicated to sort out.

"There are a lot of questions. You can't just look at the straight number that you get from the report when you're trying to decide is it safe or not safe to use these bags," Duso said.

She explains that the analysis is done by digesting the bags in a very strong acid. It breaks the material down, and releases any lead inside so that it can be measured.

Duso says the safety concern doesn't come from how much lead is in the bag, but rather how much of the toxin could come off the bag and end up inside the human body.

"A bag is not a food product, so I think you'd really need to look at the amount of lead that people are actually ingesting as a result of using those bags," she said.

Some factors to consider include whether fruits and vegetables are placed directly in the bag, or if the bag is used for long enough to fall apart.

The Canadian health and environment group Environmental Defence recommends using bags made of natural materials, and says reusable is still better than plastic.

"When you're using plastic bags, obviously you're exposing yourself to the plastics and things that come off plastics as well," the group's Matt Price said.

Health Canada says it is not aware of any complaints associated with lead in reusable grocery bags. The government agency offers tips about food safety and reusable bags on its website.

With a report from CTV British Columbia's Maria Weisgarber