The health risks to smokers from inhaling mainstream cigarette smoke are well know. In addition, there is growing evidence of risks posed to the health of non-smokers due to involuntary (passive) inhalation of Environmental Tobacco Smoke. However, epidemiological studies that investigate the relationship between ETS and health effects are seriously hindered for lack of a specific and sensitive tracer for ETS. The goals of this pilot project are to evaluate the use of solanesol as a suitable tracer for ETS in various indoor settings and compare it to nicotine, a widely used specific but not sensitive tracer for ETS.