It is plausible that cigarette smoking could cause mesothelioma. There are many carcinogens in cigarette smoke that cause other cancers. And, historically, most people who developed mesothelioma were also smokers. Thus, there are thousands of case reports and case series of smokers who developed mesothelioma. If smoking is not a cause by itself, it certainly makes sense that it could act synergistically with asbestos to increase one’s risk of mesothelioma. Our airways are lined with cilia, hair-like structures that brush out mucus, dirt, and debris (including asbestos fibers) from our lungs. “Smoking temporarily paralyzes and even kills cilia.” Smokefree.gov.
Nevertheless, the human studies have not supported a causal association. Some found no association; others reported positive but not statistically significant associations. Recently, however, researchers in Slovenia reported a statistically significant risk of mesothelioma from smoking. Franko, et al. (2018) evaluated 150 mesothelioma cases treated at a Ljubljana, Slovenia hospital during 2007-2013, and 122 controls, who had occupational asbestos exposure (from a cement manufacturing plant) but no asbestos-related disease. The authors reported an odds ratio of 9.30 [95% confidence interval (CI): 4.83–17.98].
Does this one study prove that smoking causes mesothelioma? No. Most experts would agree that we can’t rely on one statistically significant positive study while ignoring other studies finding no association or no statistically significant association. Even when we have seemingly supportive biologic plausibility, case reports, and case series, multiple epidemiologic studies demonstrating an association beyond the play of chance are necessary to prove a causal association.
– Ray Harris