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We wanted to assess relations between the daily occurrence of asthma symptoms and fluctuations of air pollution concentrations and meteorological conditions. In a panel of 31 asthmatic patients residing in the town of Pitea in northern Sweden, severe symptoms of shortness of breath, wheeze, cough and phlegm were recorded in an asthma diary together with suspected causes. Sulphur dioxide, nitrogen dioxide, black smoke, relative humidity and temperature were used to evaluate the relationship to the environment. By using multivariate analyses, we found that daily variations in the particulate pollution levels, indicated by black smoke levels below the criteria limits, had significant effects on the risk of developing severe symptoms of shortness of breath. This association was stronger among 10 subjects, who had at least five incident days with severe shortness of breath. Meteorological conditions were not significant in the multivariate models. Cough and phlegm did not show significant relationships to any environmental condition that was evaluated. Only one-third of the subjects reported, at least once during the study, symptoms believed to be related to air pollutants, although we found significant correlations between the pollution levels and the frequency of pollution-related symptoms. We conclude that an association has been established for black smoke as pollutant and shortness of breath as respiratory symptom, and that in certain asthmatics, effects were occurring at lower particulate levels than suggested previously.

The prevalence of respiratory symptoms in 6,610 adults (3,372 men and 3,238 women); 35-36, 50-51 and 65-66 yrs of age, living in selected areas of Norrbotten, northern Sweden, were assessed in a postal survey. Response rates were identical in men and women, and at least one respiratory symptom was reported by 41% of each sex. Twenty two percent reported sputum production, and 14% reported wheezing. Despite differences in smoking habits and in the different age groups, the prevalence of symptoms did not differ between the sexes, or between urban and rural areas. Symptoms were as common in people living in the rural interior as in the industrialized coastal area. Present or past history of asthma was reported by 323 (5.9%) subjects, whilst 234 (4.1%) subjects stated that they had chronic bronchitis or emphysema. Less than half of the subjects who reported attacks of breathlessness together with wheezing stated that they had at any time had asthma. Whilst the exact prevalence of had asthma. Whilst the exact prevalence of at any time had asthma and chronic bronchitis cannot be assessed from this postal survey, its results indicate that the prevalence of asthma may be higher in northern Sweden than has been reported from the south of Sweden.