Chemicals that have been associated with cancer and other health problems have been found in some fast-food packaging, according to a new study. The study in the journal Environmental Science and Technology Letters tested more than 400 samples from 27 fast food chains in the United States. Almost half of paper wrappers and 20 percent of paperboard samples -- such as boxes for fries and pizza -- contained fluorine, a marker for highly fluorinated chemicals used in stain-resistant carpets, non-stick cookware and waterproof outdoor apparel.