The South Durban area is heavily industrialized and includes residential neighbourhoods. Odour complaints and exceedences of air quality guidelines have been common for many years, although air quality levels currently fall below WHO guidelines.
This study investigated (a) prevalences of chronic respiratory symptoms and conditions, including asthma, among students and teachers in a South Durban primary school; and (b) the association of short-term fluctuations in ambient air pollutant levels with the prevalence and severity of respiratory tract symptoms and pulmonary function measures.
This longitudinal, population-based study included 273 participants (248 students; 25 teachers). All children in grades 3 and 6 were invited with participation rates exceeding 90%. Participants completed comprehensive parent and child questionnaires and baseline spirometry including methacholine challenge testing. Bi-hourly during the school day, subjects completed symptom/activity logs, and digitally recorded peak expiratory flow (PEF) and forced expiratory volume (FEV1). Parents maintained daily diaries. Sulphur dioxide (SO2), nitrogen oxides, particulate matter (PM10), carbon monoxide, total reduced sulphur, and surface meteorology were measured continuously at the school during the 18-day study period. Integrated samples of PM10 and volatile organic compounds were collected.
Among students in grades 3 and 6, prevalences of asthma and of bronchial hyperreactivity were strikingly high, exceeding comparable reports in the literature: 52.4% had asthma of any severity, 25.9% had moderate to severe asthma, 20.9% had marked airway hyperresponsiveness (PC20 ≤ 2 mg/ml of methacholine), and 49.8% had probable or marked airway hyperresponsiveness (a PC 20 ≤ 8 mg/ml). Fluctuations in both SO2and PM10 were strongly associated with adverse fluctuations in the health status of students with persistent (mild, moderate, or severe) asthma, e.g., prior day exposures to both SO2and PM10 were associated with increased lower respiratory symptoms (cough, wheezing, chest tightness and shortness of breath) and increased intra-day variability of FEV1 and PEF.
The found associations are highly statistically significant and consistent, and provide strong evidence that air pollution exposures below current guidelines are associated with acute changes in health status among students with persistent asthma in South Durban.