Snack foods don’t offer much in the way of good nutrition, and they are often packed with sugar, sodium and harmful fats. If that’s not reason enough to avoid or limit them, consider the fact that they also offer up a dose of food preservatives that could disrupt your immune system.

Food preservatives help keep our food safe and prevent us from ingesting organisms that could be harmful to our health. They also allow for the mass production of food, enabling millions of people to have access to food. On the flip side, however, many of the preservatives added to foods can raise the risk of cancer in some people or have other adverse effects.

PFAS can suppress immune function and interfere with the effectiveness of vaccines. Recently, an association was found between how sick a person gets with COVID-19 and high levels of PFAS in their blood.

The Environmental Working Group (EWG), a nonprofit organization whose mission is to protect the environment and human health, conducted a study of the most common chemicals added to the foods we eat, as well as per- and polyfluoroalkyl substances (PFAS) known to migrate to food from packaging materials or processing equipment. PFAS are sometimes called “forever chemicals” because they do not break down over time.

To measure the health hazards of these chemicals, the EWG used information from the Environmental Protection Agency’s Toxicity Forecaster, also known as ToxCast. One of the chemicals they investigated was TBHQ, or tert-butylhydroquinone, a food preservative that has been used extensively for decades. Its sole purpose is to increase the shelf life of packaged foods.

If you’ve ever eaten Pop Tarts, Rice Krispies Treats or Cheez-Its, you’ve had a taste of TBHQ. It is an ingredient in over 1,200 popular processed foods. Previous studies of TBHQ found that the chemical influenced how well flu vaccines work, and that it may be associated with an increase in food allergies.

The Environmental Working Group also reviewed prior studies that examined how PFAS get into food, whether from processing equipment or the components of the food packaging. Studies have found that these chemicals, are in the food wrappers, bags and boxes from fast food franchises, migrate to the food inside them and eventually to the people eating those foods.

PFAS can suppress immune function and interfere with the effectiveness of vaccines. Recently, an association was reported between how sick a person gets with COVID-19 and high levels of PFAS in their blood. More research is needed to understand the relationship between PFAS and immune function.

Despite new research showing harm from these chemicals, the Food and Drug Administration (FDA) allows these preservatives to be added to packaged foods. Some preservatives, like TBHQ, were approved years ago, and the FDA does not take new research into consideration or reassess the safety of chemicals added to food.

“Food manufacturers have no incentive to change their formulas,” Scott Faber, of EWG, said in a statement. “Too often, the FDA allows the food and chemical industry to determine which ingredients are safe for consumption. Our research shows how important it is that the FDA take a second look at these ingredients and test all food chemicals for safety.”

It is possible to leave these potentially harmful chemicals out of processed foods, but not all food manufacturers choose to do that. Concerned consumers can read labels to avoid foods that have TBHQ added during the manufacturing process, but it may still be present if the food packaging contains it, and the chemical leaches into the food.

The study is published in the International Journal of Environmental Research and Public Health.