If you smoke and have been thinking about quitting, here's one more good reason to do so: Secondhand smoke endangers your pets, too. Secondhand smoke, also called environmental tobacco smoke or ETS, has been associated with cancer, respiratory and cardiovascular disease in humans. Exposure levels in cats kept indoors may be higher than those in human family members, who often spend more time outside the home. A study done by Tufts School of Veterinary Medicine found "a strong correlation between ETS and an oral cancer, squamous cell carcinoma, in cats." The risk for this type of cancer doubled in cats...