Short-Term Association Between PM2.5 Exposure and Emergency Department Visits for Asthma in Urban Populations: A Systematic Review and Meta-Analytic Evidence Synthesis
DOI:
https://doi.org/10.66687/JMRISKeywords:
air pollution, emergency department, asthma, PM2.5Abstract
Background: Fine particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5) penetrates deeply into the respiratory tract and has been implicated in acute asthma exacerbations. Emergency department (ED) utilization provides a clinically meaningful measure of severe short-term deterioration.
Objective: To synthesize high-quality evidence available through 2021 concerning short-term PM2.5 exposure and asthma-related ED visits in urban populations, with particular attention to exposure-response magnitude, susceptible groups, lag structure and seasonal variation.
Methods: A structured systematic evidence synthesis was conducted using peer-reviewed studies published no later than 31 December 2021. References were restricted to Q1 journals in respiratory medicine, environmental health, epidemiology and pollution research. Time-series, case-crossover and meta-analytic studies evaluating short-term ambient PM2.5 exposure and asthma ED visits or closely related emergency/hospital utilization were eligible. Published pooled estimates were retained rather than recombined where overlapping primary studies would have resulted in double counting.
Results: Meta-analytic evidence consistently demonstrated increased acute asthma utilization following short-term PM2.5 exposure. Published pooled estimates ranged from approximately 1.5% to 2.8% increased risk per 10 μg/m³ rise in PM2.5 in mixed populations, while pediatric-specific analyses reported larger effects. A 2021 Shanghai analysis encompassing 108,817 pediatric asthma ED visits found an RR of 1.011 (95% CI 1.002–1.021) per 10 μg/m³ PM2.5 increase. Earlier Seattle evidence reported an RR of 1.15 per 11 μg/m³ increase. Effects varied by age, season, lag interval, pollutant mixture and PM2.5 composition. Children repeatedly emerged as a susceptible group.
Conclusion: Short-term increases in ambient PM2.5 are associated with modest but epidemiologically important increases in asthma-related emergency healthcare utilization. Even small relative increases can create substantial urban healthcare burden because exposure affects entire populations. Improved pollution control, exposure forecasting and targeted risk communication for people with asthma are warranted.
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