Many already know that the fast food they are consuming is not really healthy for them, what with all the cholesterol and sodium content found in the burgers and fries they consume. But now, new reports indicate that the containers of the fast food may also have chemicals that are harmful to humans.

Environmental Science and Technology Letters recently published a report that states that out of all the fast food packaging that were tested, one-third tested positive for fluorinated chemicals. These chemicals have grease-repellent properties that are why they are used in non-stick pans and the like.

CNN reports that 400 samples of packaging from fast foods all over the country were collected. The six types of packaging collected are food contact paperboard (for fries and pizza), beverage containers (milk and juice), non-contact paper (outer bags), paper cups, food contact paper (wrappers for sandwich, burgers, and pastries), and lids. These packages were taken from 27 food chains such as Starbucks, Chipotle, Jimmy Johns, Taco Time and Quiznos.

The Denver Post says that the chemicals found in the food packages bear resemblance to the chemicals that contaminated the groundwater at the south part of Colorado Springs. Dave Andrews, a chemist for the Environmental Working Group says that though there are no definitive answers for the harm that may be caused by the chemicals, there is still a reason to be concerned as these chemicals have been linked to medical conditions such as kidney and testicular cancer, and low birth weight.

Out of the six types of food packaging, it was the food contact paper that had the most percentage, with 46% of the samples positive for fluorine. Paper cups, paper bags, and lids did not contain any of the potentially harmful chemicals.

The danger is that the chemicals can transfer from the packaging to the food, as stated by Laurel Schaider, a researcher for Silent Spring Institute. She says that consumer can avoid it by asking for some of their food to be served in paper cups instead, or better yet campaign for their favorite fast food chains to do away with using food packaging containing the fluorinated chemicals.