According to reports, a new report points that food packaging used by fast food brands such as McDonald’s, Sweetgreen and Burger King may contain the potentially harmful chemical PFAS. This chemical can better prevent grease from food from seeping into the package.

PFAS (per- and polyfluoroalkyl substances) is a “permanent chemical” and is potentially linked to a variety of diseases, including decreased fertility, elevated cholesterol levels, decreased immune levels and an increased risk of cancer.

After reports spread to China, McDonald’s and Burger King in the mainland responded on Weibo that they did not use the chemical in food packaging sold in China. In addition, both companies claim that the food packaging they use “conpletely”complies with Chinese regulations.

In January 2017, McDonald’s (China) Co., Ltd. was acquired by CITIC Capital 52% stake, and subsequently changed its name to Golden Arch Co., Ltd.

Burger King, owned by Restaurant Brands International (RBI) but whose Chinese outlets are mainly managed by Tab Food Investments (TFI) . On July 15, Burger King in China was criticized by CCTV for violating its own food regulations by selling expired food.