As Canada phases out single-use plastics, more restaurants are opting to use "compostable" takeout containers. But a new study suggests these supposedly eco-friendly containers may pose hazards to our health and the environment.

In a study published in Environmental Science and Technology Letters on Tuesday, researchers looked at 42 different types of food packaging samples and found the presence of per- and polyfluoroalkyl substances (PFAS), also known as "forever chemicals," in 55 per cent of the samples.

A deeper dive into eight of these samples found that moulded paper bowls had the highest levels of PFAS. These containers are typically made out of paper, or other fibres like sugarcane, and are often advertised as "compostable" and more environmentally-friendly than plastic.

University of Toronto environmental sciences professor Miriam Diamond, who led the study, says manufacturers use PFAS for paper bowls to act as repellants for grease, oil and water.

"When you've put the hot, greasy and gloppy burrito in it, the bowl doesn't get soggy. So that's what (the PFAS) is doing. The single-use plastics don't need these because the plastics are water- and oil- and grease-resistant," she told

However, these chemicals don't easily break down, given that they're made of a strong chemical bond between carbon and fluorine.

"These chemicals don't get bound up by soils and in the bottom of lakes and oceans. They stay in the water. That means they circulate around, and it also means that these chemicals get into our drinking water," Diamond said.

Studies have shown that exposure to these chemicals have been linked to several serious health concerns. PFAS exposure has been linked to increases in cholesterol, Type 2 diabetes, weaker immune systems, reduced fertility and even cancer.

Last December, Canada's ban on the import and manufacture of single-use plastics took effect, prompting many restaurants to switch to paper-based takeout containers. A ban on the sale of single-use plastics is set to take effect this December, and Diamond worries PFAS-containing paper packaging will only become more common as the plastic phase-out continues.

PFAS have already been banned for food packaging in 11 U.S. states. In California, the ban also extends to textiles and cosmetics. In the European Union, legislators are also considering a proposal to ban on 10,000 different types of forever chemicals.

Some companies, such as McDonald's and Restaurant Brands International, parent company of Tim Horton's and Burger King, have announced that they plan on phasing out PFAS in the packaging by 2025.

"Half the products we tested didn't have PFAS. So that means that there certainly are alternatives on the market. You just don't know which one does or doesn't have it," she said.

But in Canada, Diamond worries about the slower pace of legislative action on PFAS compared to the U.S. and Europe. In 2021, the federal government announced it would begin researching and monitoring PFAS and reviewing policies in other jurisdictions to determine what regulation may be needed to address these substances. The government said it plans to publish a "state of PFAS report," scheduled to come out by this year.

"Canada is not going to be a leader here, but at least we could be quicker to come on board with what other jurisdictions are doing," Diamond said.