Asthma in the vicinity of power stations: II. Outdoor air quality and symptoms

To assess longitudinally the effect of living in the vicinity of coal‐fired power stations on children with asthma, 99 schoolchildren with a history of wheezing in the previous 12 months were studied for 1 year, using daily diaries and measurements of air quality. The children had been identified in a cross‐sectional survey of two coastal areas: Lake Munmorah (LM), within 5 km of two power stations, and Nelson Bay (NB), free from major industry. Daily air quality [sulphur dioxide (SO 2 ) and nitrogen oxides (NO x )], respiratory symptoms, and treatment for asthma were recorded throughout the year. Measurements of SO 2 and NO x at LM were well within recommended guidelines although they were several times higher than at NB: maximum daily levels in SO 2 (μg/m 3 ) were 26 at LM, 11 at NB (standard, 365); yearly average SO 2 was 2 at LM, 0.3 at NB (standard, 60); yearly average NO x (μg/m 3 ) was 2 at LM, 0.4 at NB (standard, 94). Marked weekly fluctuations occured in the prevalence of cough, wheezing, and breathlessness, without any substantial differences between LM and NB. Overall, the prevalence of symptoms was low (10% for wheezing, 20% for any symptom). Whether the daily SO 2 and NO x levels affected the occurrence of respiratory symptoms was investigated in children at LM using a logistic regression (Korn and Whittemore technique). For these children as a group, air quality measurements were not associated with the occurrence of symptoms.