Many fast food wrappers and containers have a grease-repellent chemical coating, which according to a report in the journal Environmental Science & Technology Letters, may contain chemicals that can leach into your food. As the Centers for Disease Control and Prevention (CDC) explains, these fluorinated substances, a class of chemicals called PFASs (polyfluoroalkyl and perfluoroalkyl), have been linked to an increased risk of certain cancers, decreased fertility, hypertension in pregnancy, low birth weight, thyroid disease, obesity, high cholesterol and immune suppression in human and animal studies.PFASs are used in products that give it stain-resistant, water-repellant and non-stick properties. Since they are made with bonded compounds of carbon and fluorine, they resist breaking down, which suggests they can accumulate in water, soil, sediment – and the human body.Researchers from the Silent Spring Institute; the University of California, Berkeley; the University of Notre Dame; and other institutions measured the amount of fluorine in more than 400 fast food packaging samples across the United States. The study found one-third of them contained some form of the chemical fluorine. The good news is that most fast-food packaging did not contain any fluorine, said Laurel Shaider, lead study author with the Silent Spring Institute. This indicates that some manufacturers might be using fluorine compound-free chemicals to get the water- and grease-resistant effects they want without using compounds that carry a health risk, she says.Cutting down on fast food and eating more fresh foods can drastically lower your exposure. Michael Hansen, Consumer Reports’ senior scientist, advises consumers limit the amount of contact time food is left in its packaging. If you can, once you arrive home or at work, take the food out of wrappers and use your own plates and bowls instead.You may also want to consider the type of packaging your food is delivered in. Overall, researchers found that 46 per cent of paper wrappers tested positive for PFASs. This included 56 per cent of dessert and bread wrappers, 38 per cent of sandwich and burger wrappers, and 20 per cent of paperboard (like the cardboard boxes that French fries and pizza tend to come in). Paper cups were the only packages to test negative for fluorinated chemicals.As for leftovers: “You shouldn’t be storing food or reheating it in those packaging materials,” Hansen says.