The highest levels of indicators for PFAS were found in food packaging from Nathan's Famous, Cava, Arby's, Burger King, Chick-fil-A, Stop & Shop and Sweetgreen, according to an investigation released Thursday by Consumer Reports.

Often called "forever chemicals" because they do not break down in the environment, PFAS are used in food packaging to prevent grease and water from soaking through food wrappers and beverage cups.

PFAS can also be found in the ink used to print logos and instructions on food containers.

The new report comes more than two years into the Covid-19 pandemic, when the public has relied heavily on takeout and grocery deliveries.

The US Centers for Disease Control and Prevention calls exposure to PFAS (per- and polyfluoroalkyl substances) a "public health concern," citing studies that found the human-made chemicals can harm the immune system and reduce a person's resistance to infectious diseases.

"There is evidence from human and animal studies that PFAS exposure may reduce antibody responses to vaccines," stated the CDC and the Agency for Toxic Substances and Disease Registry. "More research is needed to understand how PFAS exposure may affect illness from COVID-19."

More than 100 food products tested

The Consumer Reports investigation collected 118 food packaging products sold by 24 companies in the tristate area of New York, New Jersey and Connecticut.

It tested those products for organic fluorine — a marker for PFAS. Researchers then sent samples of products with the highest levels to an independent laboratory that could perform more specific tests, said Michael Hansen, senior staff scientist for advocacy at Consumer Reports.