This study in Science provides added information on the causal pathway between tobacco exposure and cancer.  It’s a reminder that the mechanisms are potent and profound…

http://science.sciencemag.org/content/354/6312/618

Mutational signatures associated with tobacco smoking in human cancer
Science  04 Nov 2016:
Vol. 354, Issue 6312, pp. 618-622
DOI: 10.1126/science.aag0299