The bowls used at restaurants such as Chipotle and Sweetgreen are linked to cancer-causing chemicals, according to a new study.

Though compostable bowls are often advertised as environmentally friendly, they may be treated with toxic compounds known as “forever chemicals,” according to a New Food Economy Study, which tested 14 locations of eight New York City restaurants.

Among the restaurants were fast-casual favorites such as Fresh & Co, Chipotle, Sweetgreen, Dos Toros and Dig Inn.

Tests performed on the containers determined that they contained high levels of fluorine, which indicates per- and polyfluoroalkyl chemicals (PFAs) were likely used to make them more durable, according to researchers.

“If a product is showing really high fluorine levels, companies really can’t claim they didn’t use PFAS,” said Rainer Lohmann, who serves as director of the University of Rhode Island’s Lohmann Lab, according to New Food Economy.

The presence of the chemicals has been linked to health problems such as kidney and testicular cancers, thyroid disorders, decreased sperm quality and pregnancy-induced hypertension, researchers said. Furthermore, the chemicals don’t degrade naturally in the environment.

“They are likely making compost more toxic, adding to the chemical load of the very soil and water they were supposed to help improve,” researcher Joe Fassler wrote. “And rather than degrade quickly, they contain potentially hazardous ingredients that never break down. Not in five years, and not in 500.”

Chipotle said in a statement Wednesday that the chain strives to meet regulatory requirements.

“As evidenced in Chipotle’s Sustainability Report, we are committed to using safe and sustainable food packaging and only partner with suppliers who make fluorochemical sciences and food safety a top priority,” the statement said. “These suppliers operate under strict guidelines set forth by the FDA, and have all provided Chipotle with certification that all raw material and finished pulp products fully meet regulatory requirements.”

Reps for the other restaurants didn’t immediately respond to request for comment.