From the Wikipedia page:
From March 1952 until at least May 1956, however, the Micronite filter in Kent cigarettes contained compressed blue asbestos within the crimped crepe paper, which is the most carcinogenic type of asbestos. It has been suspected that many cases of mesothelioma have been caused specifically by smoking the original Kent cigarettes, and various lawsuits followed over the years because of it.
Jesus Christ.