Cigarette smoke is another factor that can be harmful to the environment. Rumor has it that second hand smoke is worst than actually smoking yourself. According to  http://www.keenforgreen.com/b/cigarettes-and-environment cigarette smoke contains up to 4,000 chemicals. in 2004, a small Italian study lead by Giovanni Invernizzi from the Tobacco Control Unit of Italy's National Cancer Institute in Milan found that air pollution that comes from cigarettes is 10 times greater than diesel car exhaust.