My uncle isnt going to quit smoking, so what are things other than quitting he can do to reduce risk of cancer and other tobacco related diseases?

Many things: first and foremost, CUT DOWN. The less you smoke, the less damage it does. Change the way you smoke - don't inhale deeply and breathe out through your nose to increase absorption of both nicotine and "tars." Consider e-cigarettes, which while not considered "safe," are certainly safer than combusted cigarettes. He can reduce YOUR chances (and others) of cancer etc. by not smoking around you.