Dogs and cats are twice as likely to get cancer if their owner smokes.
Reif, John, Christa Bruns, and Kimberly Lower. “Cancer of the Nasal Cavity and Paranasal Sinuses and Exposure to Environmental Tobacco Smoke in Pet Dogs.” American Journal of Epidemiology. 147(5). 1998. Web.http://aje.oxfordjournals.org/content/147/5/488.long