Lagged acute respiratory outcomes among children related to ambient pollutant exposure in a high exposure setting in South Africa
Shumani Phaswana, Caradee Y. Wright, Rebecca M. Garland, Thulie N Khumalo, Rajen N. Naidoo
Abstract
Background: Acute ambient air pollution impacts on the respiratory health of children may be lagged across time. We determined the short-term lagged effects of particulate matter (PM 2.5 ), sulphur dioxide (SO 2 ), and oxides of nitrogen (NO x ) on the respiratory health of children living in low-income communities. Methods: A school-based study was conducted using a repeated measures design, across summer and winter, in four schools in each of four suburbs in the Vaal Triangle, South Africa. Data for PM 2.5 , NO x , and SO 2 were obtained from monitoring stations within close proximity of the schools. Over 10 school days in each phase, grade 4 children completed a symptoms log and lung function tests. Parents completed a child respiratory questionnaire. Generalized estimation equations models adjusted for covariates of interest in relation to lung function outcomes and air pollutants including lag effects of 1–5 days. Results: Daily PM 2.5 , NO x , and SO 2 median concentration levels were frequently higher than international standards. Among the 280 child participants (mean age 9 years), the prevalence of symptoms based on probable asthma was 9.6%. There was a consistent increased pollutant-related risk for respiratory symptoms, except for NO x and shortness of breath. Lung function, associated with pollutant fluctuations across the different lags, was most pronounced for peak expiratory flow rate (PEFR) for PM 2.5 and SO 2 . A preceding 5-day average SO 2 exposure had the largest loss (7.5 L/minute) in PEFR. Conclusions: Lagged declines in daily lung function and increased odds of having respiratory symptoms were related to increases in PM 2.5 and SO 2 among a school-based sample of children.