Cigarettes are non only bad for smokers' health, but they are bad for the environment too. Cigarette filters are a major source of plastic pollution, say researchers from the London School of Hygiene and Tropical Medicine and San Diego State University. An estimated 6 trillion butts made largely out of plastic and weighing around a million tonnes are produced every year. They are the biggest contributor, by number of items, to the plastic discarded into the environment. The best way is to never smoke.