I've been exposed to second hand smoke.how at risk for cancer am i?

Depends on the: Exposure. Serious second-hand smoke exposure causing the potential for an increase in head/neck cancer and lung cancer (on the order of 10-20% over baseline) has been reported in people who work in bars/restaurants where smoking is permitted, and in people living in homes where there are smokers, or other regular and heavy exposure to smoke. If your exposure was limited, your risk is very small.