Assessment of exposure to environmental tobacco smoke.

We present a theoretical framework for assessment of exposure to environmental tobacco smoke (ETS), and review current methods in order to provide guidelines for different types of studies. Exposure assessment should include both a quantitative dimension and consideration of time-specificity of exposure. The ultimate aim is to measure the concentrations of ETS encountered by an individual for different time periods in various microenvironments. The first step is to identify an indicator of ETS. Personal monitoring of air nicotine and respirable suspended particulates (RSPs) are the most direct assessment methods. Indirect assessment methods include stationary measurements of tobacco smoke constituents in different microenvironments and/or questionnaire-derived information, modelled with time-activity information. Biomarkers, such as nicotine and/or cotinine in body fluids or hair, can be used as surrogate measures of dose, although they are usually affected by individual processes in the body after exposure. The best approach to assess ETS exposure will depend on the aim of the study, the health outcome, and the resources. Personal monitoring of nicotine or RSPs is the best method in studies of short-term health effects with small study samples. Stationary measurements of indoor air nicotine or RSPs are suitable for overall monitoring of ETS in different microenvironments over time. Questionnaires and interviews are suitable when studying health outcomes with a long latency period and rare diseases requiring large study populations. Cotinine in body fluids and nicotine concentration in hair can be used to assess cumulative exposure over days or months, respectively. A combination of different methods is often the best approach.