The cross-sectional part of SAPALDIA studied the associations between respiratory symptoms or functional abnormalities and chronic exposure to a polluted environment. The results showed an elevated risk of developing respiratory symptoms in regions with higher levels of particulate matters (PM10). The same was observed with passive smoking exposure. Decreased spirometric parameters (especially FVC) were measured in areas with the highest levels of PM10. While the functional alteration is clinically minimal in the individual, the effect is significant when one considers the prevalence of an abnormal functional parameter in a general population. Exposure to pollutants at the workplace increases bronchial reactivity to non-specific stimuli, with atopy acting as amplifier of this effect. The longitudinal part of SAPALDIA examined the associations between the dynamics of respiratory symptoms or functional abnormalities and average levels, as well as short-term fluctuations, of atmospheric pollutants. It was observed that symptomatic episodes tend to last longer in more polluted regions, whichever marker of pollution is used (PM10 or NO2). Passive smoking tends to prolong respiratory symptoms and shorten asymptomatic intervals. Short-term increases in outdoor pollutants are associated with an increase in incidence of peak flows below individual baseline values. Numerous questions remain regarding the relationship between respiratory health and environment. A SAPALDIA II study is under preparation which will follow the evolution of SAPALDIA I participants with regard to respiratory symptoms, pulmonary function, bronchial reactivity and markers of atopy.