NewScientist reports that 3 cigarettes are ten times worse than 1 diesel engine, when particulate pollution is accumulated over 30 minutes of idling or cigarette-burning. This is from an Italian study conducted in a private garage in the small Alpine town of Chiavenna. The number of the tiniest particles was particularly bad from the cigarettes; the smaller ones cause worse health problems. Yet more reason not to smoke, if you care about the environment!