McDonald's and Burger King Sued for Use of 'Forever Chemicals' New report finds harmful chemicals in packaging from 24 popular food and grocery chains, prompting class-action suits against two of the biggest retailers on the list.

Consumer Reports recently found per-and polyfluoroalkyl substances (PFAS) – otherwise known as "forever chemicals" – in more than 100 food packaging products from 24 popular retailers, prompting what some say is just the beginning of a wave of class-action lawsuits.

On the surface, PFAS look nonthreatening. They often resemble paper or cardboard and typically lack any obvious sign of danger, but the chemical is practically impossible to break down, and it has had proven consequences on both consumer health and the environment. The grease-resistant compound is advantageous to food retailers and grocers who want to guarantee their products stay fresh, intact and entirely leak-proof, which is why the versatility of brands found to be using PFAS comes as no surprise.

Fast-food chains such as Burger King and McDonald's had the most PFAS in bags for fries, chicken nuggets, cookies and burgers. However, it's not just fast food. The report also found high levels of PFAS in packaging from chains that supposedly promote health, like Cava and Sweetgreen.

In the test of more than 100 food packaging containers from 24 retailers, the report found that PFAS were found in at least some packaging from every single retailer. Among the other brands with the most exposure to PFAS were Nathan's Famous and Stop & Shop. Among the least were Five Guys, Popeyes, Shake Shack and Wendy's.

Related: Subway to Remove Chemical From Sandwich Bread Following Blogger's Protest

The prevalence of the chemical has serious implications on consumers, with some research finding that higher levels of PFAS were found in people who eat out more often. While it might seem like indirect exposure, the toxins in the packaging still make their way into the food.

"We know that these substances migrate into food you eat," Justin Boucher, an environmental engineer at the Food Packaging Forum, shared with Consumer Reports in response to its findings. "It's clear, direct exposure."

And it doesn't stop there. When these packages are thrown away, there are risks of the harmful compounds ending up in landfills, further contaminating water, soil and spreading toxins throughout the air.

While two dozen brands were used in the study, only Burger King and McDonald's have been met with class-action suits so far, with most of the claims centered on false advertising. Burger King opted out of a comment on the lawsuits when prompted by TODAY, but reassured them that they are committed to removing PFAS from all packaging by 2025 or sooner. McDonald's also told the outlet that the claims are "baseless," as the brand has made significant progress in eliminating the chemicals from packaging, and its previous commitment to expel the chemical entirely by 2025 still holds true.

Related: Burger King is sued for misleading advertising on the size of its products