So much of smoking’s ill effects are felt in the lungs, and lung cancer is far more prevalent than oral cancer. Lung cancer killed about 160,000 Americans last year, according to the American Cancer Society — 20 times the total for oral cancer. (Some forms of smokeless tobacco also have been linked, less definitively, to an increased risk of pancreatic cancer or esophageal cancer.) Yet some anti-tobacco groups suggest that chewing tobacco is just as dangerous as smoking it.