We hate to be the bearers of bad news, but as it turns out, your fast food order might be coming with a side of harmful chemicals. According to a new study published in the journal Environmental Science & Technology, many fast food chains are using wrappers that contain dangerous chemicals. For the study, researchers at the University of Notre Dame tested over 400 food packaging items from leading fast food chains, including McDonalds, Burger King, Starbucks, Chipotle, and Chick-Fil-A in and around Boston, San Francisco, Seattle, Washington, D.C., and Grand Rapids. By studying the wrappers, researchers found evidence of fluorinated chemicals, which may be used to repel grease in food. However, the chemicals are also toxic. "This is a really persistent chemical," Graham Peaslee, a professor of experimental nuclear physics in the College of Science at the University of Notre Dame, who tested the samples, said in a news release. "It gets in the bloodstream, it stays there and accumulates. There are diseases that correlate to it, so we really don't want this class of chemicals out there." According to the release, the chemicals have previously been linked to kidney and testicular cancers, thyroid disease, low birth weight, and immunotoxicity in children, among other health issues. The release also states that previous studies have found that the chemicals can migrate into food and, when consumed, accumulate in the body. "This is a wake-up call for those companies and the consumers," Peaslee said. The researchers recommended that fast food chains begin using nontoxic wrappers, such as wax paper or aluminum foil. In the meantime, the authors also published a guide to avoiding dangerous chemicals.