This from an organization called "Physicians Committee for Responsible Medicine" or "PCRM." We never ate at KFC before the vegan change, but a lot of people do, of course.
The "study" seems to be rather limited and it doesn't say whether the carcinogen actually raises the risk of cancer in human beings. In The China Study, Campbell writes that he and fellow researchers discovered a carcinogen in the peanut butter that Filipino children were eating. He and his colleagues were in that country to inquire into the high rate of liver cancer among children there.
What struck him was that the wealthier the family, the higher the incidence of the cancer. He also observed that the wealthier the family, the more meat the children would eat, in addition to the peanut butter. From that observation, he developed the hypothesis that there is a link between animal protein and the development of cancer from carcinogens that might otherwise have no affect on the body. Later studies he considered seemed to him to establish that hypothesis.
Of course, with KFC chicken one gets both the carcinogen (if the PCRM study is to be believed) and the meat. Such a deal.
I'm glad I don't have to worry about it.