Abstract:
BACKGROUND: Asthma affects millions of people globally, and high levels of air pollution aggravate asthma occurrence. This study
aimed to determine the association between short-term lagged PM2.5 exposure and airway inflammation, lung function, and asthma
symptom scores among schoolchildren in communities in the Highveld high-pollution region in South Africa.
METHODS: A cross-sectional study was conducted among schoolchildren aged 9–14 years in six communities in the Highveld
region in South Africa, between October 2018 and February 2019. A NIOX 200 instrument was used to measure fractional exhaled
nitric oxide (FeNO). Lung function indices (forced expiratory volume in one second [FEV1
]; forced vital capacity [FVC] and FEV1
/FVC)
were collected using spirometry and the percent of predicted of these was based on the reference equations from the Global Lung
Initiative, without ethnic correction. These values were further analyzed as binary outcomes following relevant thresholds (lower limits
of normal for lung function and a cutoff of 35 ppb for FeNO). Asthma symptoms were used to create the asthma symptom score.
Daily averages of PM2.5 data for the nearest monitoring station located in each community, were collected from the South African
Air Quality Information System and created short-term 5-day lag PM2.5 concentrations. Additional reported environmental exposures
were collected using standardized instruments.
RESULTS: Of the 706 participating schoolchildren, only 1.13% of the participants had doctor-diagnosed asthma, compared to a
prevalence of 6.94% with an asthma symptom score suggestive of asthma. Lag 1 (odds ratio [OR]: 1.01; 95% confidence interval
[CI]: 1.00, 1.02, P = 0.039) and 5-day average lagged PM2.5 (OR: 1.02; 95% CI: 0.99, 1.04, P = 0.050) showed increased odds of the
FeNO > 35 ppb. Lung function parameters (FEV1
< lower limit of normal [LLN] [OR: 1.02, 95% CI: 1.00, 1.03, P = 0.018], and FEV1
/
FVC < LLN [OR: 1.01; 95% CI: 1.00, 1.02, P < 0.001]) and asthma symptom score ≥ 2 (OR: 1.02; 95% CI: 1.00, 1.04, P = 0.039)
also showed significant associations with lag 2, lag 4 and lag 1 of PM2.5, respectively.
CONCLUSION: Lagged PM2.5 exposure was associated with an increased odds of airway inflammation and an increased odds of lung
function parameters below the LLN particularly for the later lags, but a significant dose–response relationship across the entire sample
was not consistent.
