Many different chemical substances cause cancer. Dozens of chemicals in tobacco smoke, including nicotine, have been shown to cause cancer ( Figure below ). In fact, tobacco smoke is one of the main sources of chemical carcinogens. Smoking tobacco increases the risk of cancer of the lung, mouth, throat, and bladder. Using smokeless tobacco can also cause cancer. Other chemicals that cause cancer include asbestos, formaldehyde, benzene, cadmium, and nickel.
Context: Walter and Jesse, two coworkers, are sitting at a hotel bar having a drink together after a long day at a conference when the subject of bad habits comes up. Jesse shares that he has always struggled with biting his nails and no matter what he seems to do he can't kick the habit. Walter's bad habit is that when he plays his weekly baseball game he will use chewing tobacco. He says he doesn't even particularly like the taste anymore, but once he gets to the park he has a craving for it.
Question: Which man's chance of having mouth cancer is higher?