Compostable takeout bowls contain 'forever chemicals,' study finds

If you bought a salad bowl for lunch in a compostable cardboard container, that greener choice may have come with a dash of "forever chemicals" called PFAS — and so do other kinds of paper food packaging in Canada, a new study suggests.

Should you worry? Here's a closer look at what those chemicals are, what food packaging they're found in most, and what the findings of the study mean.

PFAS (per- and polyfluoroalkyl substances) are a group of more than 9,000 human-made chemicals that contain fluorine bonded to carbon, a strong chemical bond that makes them hard to break down. That means they accumulate over time in the human body and the environment.

PFAS have been used for lubricants, stain repellents, waterproofing, non-stick coatings and firefighting foams, and can be found in products ranging from carpets to cosmetics to clothing to food packaging.

Very few PFAS have been studied in detail, but those that have been are linked to a variety of health effects in humans and animals, including increased risk of cancers, reduced immune response and fertility, and altered metabolism and increased risk of obesity.

Three groups of well-studied PFAS (PFOS, PFOA and LC-PFCAs) are prohibited in Canada because of their risk to the environment. PFOA and PFOS are among the six PFAS that the U.S. Environmental Protection Agency proposed regulating in drinking water earlier this month.

"We know that some PFAS are toxic," said Miriam Diamond, professor at School of the Environment at the University of Toronto and senior author of the new study. "We don't know whether all PFAS are toxic because there are too many to study."

Health Canada says there's evidence other PFAS that are replacing banned PFAS are also associated with environmental or human health effects. That's why the government is considering regulating all PFAS as a group.

In the meantime, levels of PFAS are detectable in the blood of Canadians and the Government of Canada is continuing to monitor for certain chemicals. As of 2016 and 2017, 98.5 per cent of Canadians had PFAS in their blood. It has even been found in the blood of people in remote northern Indigenous communities in levels that were sometimes similar to levels in people further south.

PFAS are commonly used to make paper grease-resistant, so they are used in many fast food containers and wrappers. In that sense, finding them was no surprise. But the researchers wanted details about Canadians' exposure to PFAS through paper food packaging.

In the new study, published Tuesday in the journal Environmental Science and Technology Letters, researchers from Canada, the U.S. and Switzerland tested 42 kinds of paper food packaging collected in Toronto between February and March 2020, including compostable paper bowls, sandwich and burger wrappers, popcorn serving bags, and bags for desserts such as donuts. 

Many of these kinds of packaging may become more common in Canada following a ban on the sale of many kinds of plastic takeout containers starting last December.

One thing that food packaging manufacturers have started doing to reduce the risk of PFAS exposure is making bigger PFAS molecules. They're billed as being too heavy to "escape" from the packaging, noted the researchers of the new study in a news release. The researchers wanted to look into the impact of that as well.

The researchers, led by Heather Schwartz-Narbonne, a graduate student in environmental chemistry at the University of Toronto, first tested the packaging for fluorine, a key element in PFAS.