Keywords: air pollution, asthma, children, epidemiology, child health, particulate matter, sulphur dioxide, nitrogen dioxide, primary schools, South Africa, respiratory symptoms
The relationship between asthma and ambient air pollutants among primary school students in Durban, South Africa
We examined the prevalence of asthma among students in Grades 3 and 6 at a primary school located in the highly industrialised South Durban Industrial Basin. After baseline interviews and methacholine challenge testing (MCT), students completed bihourly symptom logs during an 18-day study period. Continuous measurements of ambient contaminants at the school included sulphur dioxide (SO2), oxides of nitrogen (NOx), and respirable particulate matter less than 10 µm (PM10). Generalised estimating equations were used to examine associations between lagged fluctuations in ambient air pollutant concentrations and daily reported symptoms. Among the 248 participants, 52% had asthma of any severity; including 11% with moderate to severe persistent asthma. On MCT, 21% of the children had marked (PC20 ≤ 2 mg/ml), 29% had probable, and 19% had possible airway hyperreactivity. Concentrations of air pollutants at the school during the study period fell below international and South African standards and guidelines. Increased lower respiratory symptoms (cough, wheezing, chest tightness or heaviness, and shortness of breath) were strongly and consistently associated with prior day fluctuations in ambient levels of both SO2 and PM10 in both single-pollutant and two-pollutant models. We note the important role of local stakeholders in implementing and conducting this study.