Significance of exposure to sidestream tobacco smoke.

The presence of toxins and carcinogens in ambient air polluted with tobacco smoke is largely due to the sidestream smoke emissions from the smouldering tobacco products. Levels of these toxins and carcinogens in sidestream smoke often exceed their concentrations in mainstream smoke. Dosimetry of tobacco-specific markers of exposure in physiologic fluids suggests that in regard to nicotine--which is the major tobacco alkaloid--exposure of humans to environmental tobacco smoke causes but a few percent of the nicotine levels reached as a result of active inhalation of cigarette mainstream smoke. Yet, this measurement of exposure is not universally applicable to all of the tobacco smoke pollutants in this complex matrix. Existing knowledge of the chemical composition of sidestream smoke and evidence of biological activity of sidestream smoke components suggests that this environmental pollutant has carcinogenic potential. Significance of exposure to environmental tobacco smoke must be evaluated on the basis of the severity of the pollution, the duration of exposure and personal variations in uptake.