Second-Hand Smoke

Second-hand smoke has two elements: mainstream smoke and sidestream smoke. Mainstream smoke is the component smokers breathe in from the burning cigarette. They inhale most of it, but they also exhale it and some escapes through the filter. Mainstream smoke makes up about 15 per cent of second-hand smoke. Sidestream smoke is created by the smoldering of the cigarette. It is produced at a lower temperature than mainstream smoke and this temperature difference causes variation in the chemical composition of the two components.

Both components contain carcinogens and about 4,000 other poisons, and while we all know the smoker gets the highest dose, the health risks associated with exposure to second-hand smoke are also well accepted. Evidence from at least one study indicates that the condensate from sidestream smoke is more likely to cause skin tumours in mice, compared to the condensate from mainstream smoke. The study authors concluded that second-hand smoke inhaled by non-smokers might be more carcinogenic than the mainstream smoke consumed by smokers.