Cigarette smoke makes a small but detectable contribution to smog, reveals a study conducted by Glen Class, an environmental engineer at the California Institute of Technology. The study reveals that cigarette smoke comprises 1 to 1.3 per cent of the fine particles polluting the air around Los Angeles. Although Class acknowledges that cigarette smoke makes only a small contribution to the total, it has been pinpointed as one of a half dozen or so minor sources that collectively account for about a quarter of the pollution.