What is meant by “mainstream” and “sidestream” smoke?
The smoke that is inhaled and then exhaled from the smoker’s lungs is called mainstream smoke (MS). Sidestream smoke (SS) is the smoke that enters the air directly from the burning end of a cigarette, cigar, or pipe. The burning end of a cigarette is not usually hot enough for complete combustion of the tobacco to occur. Since some chemicals are favoured by this incomplete burning, undiluted sidestream smoke contains higher concentrations of several chemicals than the mainstream smoke inhaled by the smoker. These chemicals include 2-naphthylamine, N-nitrosodimethylamine, 4-aminobiphenyl, and carbon monoxide. Environmental tobacco smoke (ETS) is composed of both mainstream and sidestream smoke. ETS is diluted by the air in the room before it is inhaled and is therefore less concentrated than mainstream or sidestream smoke. Every person – both smokers and non-smokers – in a room with ETS will have similar exposure because nearly 85 percent of ETS in a room comes from sidestream smoke. Th
