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 (PM2.5), sulphur dioxide (SO2), and oxides of nitrogen (NOx) 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 PM2.5, NOx, and SO2 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 PM2.5, NOx, and SO2 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 NOx and shortness of breath. Lung function, associated with
pollutant fluctuations across the different lags, was most pronounced for peak expiratory flow rate (PEFR) for PM2.5 and SO2. A preceding
5-day average SO2 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 PM2.5 and SO2 among a school-based sample of children.
