TPS 681: Short-term health effects of air pollutants 1, Exhibition Hall, Ground floor, August 26, 2019, 3:00 PM - 4:30 PM
Background/Aim: Increased atmospheric particulate matter (PM) concentrations are commonly observed during dust storm events in Iran, but there is still no evidence of their effects on human health. We aimed to evaluate the association between daily mortality and exposure to PM10 during dust events in Tehran and Ahvaz, two major cities with different sources, intensity, and frequency of desert dust episodes.
Methods: We identified desert dust episodes based on exceeding a daily PM10 concentration threshold of 150 μg/m3 jointly with a low PM2.5/PM10 ratio, typical of dust storms. We used a time-stratified case-crossover design to estimate the short-term effects of PM10 concentrations on daily mortality during non-dust days and dust episodes. Data was analysed using conditional Poisson regression, and we derived the attributable number of deaths for a counterfactual scenario of the World Health Organisation threshold for PM10 24-hour average of 50 μg/m3.
Results: Higher concentrations of PM10 and frequency of dust episodes were observed in Ahvaz than Tehran. In Ahvaz, the average lagged effects up to 3 days were higher during non-dust days (1.1%, 95%CI=[0.7 to 1.5%], for a PM10 rise of 10 μg/m3) and low-intensity dust episodes (1.4%, 95%CI = [0.6 to 2.1%]) compared to the medium and high-intensity ones (0.9%, 95% CI = [0.6 to 1.2%] and 0.5%, 95%CI = [0.1 to 0.8%], respectively). In Tehran, effects were higher during non-dust days (0.9%, 95%CI = [-0.1 to 2.0%]) than high-intensity dust episodes (0.6%, 95% CI = [-3.5 to 4.8%]), but not statistically significant. The attributable proportion of deaths was four times larger in Ahvaz during dust episodes (15.6%) than in non-dust days (3.7%) and twice in Tehran (7.9% and 3.3%, respectively).
Conclusion: We found novel evidence for the effects of PM10 on daily mortality, suggesting harmful effects when accounting for the whole range of PM10 concentrations during dust events in the Middle East.