Prevalence of respiratory and hyperreactivity symptoms in relation to levels of criteria air pollutants in Sweden

Our knowledge of the adverse health effects from exposure to low levels of air pollution is still insufficient. Early indicators, such as respiratory symptoms, need more attention. We made use of the fact that possible weak effects can be detected more easily when the relevant exposure and other determinants are well controlled. A postal questionnaire was sent to random samples of inhabitants registered as residing in the Vicinity of 55 centrally located air quality monitoring stations in Swedish towns. There were 6,109 questionnaires (76%) returned. Multivariate analyses with confounding control were used to examine the effects of different levels of criteria pollutants on the prevalence of symptoms. The ranges of the half year values were 9-32 and 2-16 mu g/m(3) for nitrogen dioxide and sulphur dioxide respectively. Logistic regression analyses showed higher risks for respiratory problems such as coughs, throat irritation and nose irritation among the persons most exposed, The associations were most obvious for nitrogen dioxide exposure among women. The suggested effects of air pollution exposure cannot be medically evaluated today but they are nevertheless interesting since they are found within common levels usually considered to be safe.