Study of the effects of indoor air pollutants nitrogen dioxide and tobacco smoke on the airways of women in Vlagtwedde and Vlaardingen. Drainless geysers were found to be the main source of NO2 pollution. Negative relationships were found between lung function and NO2 concentration in non-smoking women in an area with little outdoor pollution. This relationship was not demonstrated in (ex-)smokers or women, living in an area with relatively high outdoor air pollution.