Cars give off Carbon Monoxide just like cigarettes, except they don't give off 100 other carcinogens.
Wake up and smell your car exhaust tail pipe (no cheating here: engine should be running). Carbon Monoxide is not the only toxic that comes out from exhaust tail pipes. A smog technician can tell you more in details. Besides, has anyone ever worry that cigarette smoke is considered an air pollution contributor? Last time I checked, it is the automobile exhausts that people are most concerned about.