Ambient Air Pollution Exposure and Its Association with Emergency Respiratory Visits in an Urban Population

Abstract

Background: Ambient particulate air pollution is a major environmental determinant of acute respiratory morbidity, particularly in rapidly urbanizing regions such as Punjab, Pakistan, where recurrent smog episodes coincide with increased healthcare demand. However, locally derived, hospital-based estimates quantifying short-term pollution-related emergency respiratory burden remain limited. Objective: To evaluate the association between short-term ambient air pollutant exposure, particularly PM₂.₅, and daily emergency department (ED) respiratory visits in an urban tertiary-care setting. Methods: A hospital-based ecological time-series study was conducted from 1 January to 31 December 2023. All ED visits with a primary respiratory diagnosis were included. Daily ambient pollutant concentrations (PM₂.₅, PM₁₀, NO₂, SO₂, O₃, CO) were obtained from official monitoring stations and linked to daily respiratory visit counts. Associations were estimated using negative binomial regression models adjusted for temperature, humidity, day of week, and seasonal trends, with evaluation of lag structures (0–3 days) and short moving averages. Results: A total of 1,680 respiratory ED visits were recorded (mean 26.5/day). Each 10 µg/m³ increase in same-day PM₂.₅ was associated with a 3.2% increase in daily respiratory visits (IRR 1.032; 95% CI 1.018–1.046; p < 0.001), with stronger effects observed for the 3-day moving average (IRR 1.041; 95% CI 1.022–1.061). Associations were more pronounced for asthma (IRR 1.048) and COPD exacerbations (IRR 1.039) than for pneumonia/LRTI. Conclusion: Short-term increases in ambient PM₂.₅ are significantly associated with heightened emergency respiratory demand, supporting integration of air-quality surveillance into hospital preparedness and urban pollution-control strategies.