Association of short-term exposure to air pollution with mortality in a middle eastern tourist city

This study investigated the association of short-term exposure to PM10, PM2.5, NO2, O3, and CO with daily all-cause, cardiovascular, ischemic heart disease (IHD), cerebrovascular, and respiratory deaths in Mashhad, a tourist megacity in Iran (2014–2018). A distributed-lag-day, nonlinear model (DLNM) and generalized additive model (GAM) based on the quasi-Poisson distribution were used to explore the exposure-lag-day-response associations. The average (± standard deviation) concentrations of PM10, PM2.5, NO2, O3, and CO were 67.1 (± 35.5), 29.6 (± 14.2), 57.3 (± 24.1), 55.9 (± 16.9), and 1907.6 (± 1362.7) μg/m3, respectively. NO2 was associated with IHD mortality in lag-days 0 to 0–7, and lag-day 1. The relative risks (RRs) for a 10 μg/m3 increase in NO2 ranged from 1.01 (95% CI 0.93, 1.11) at lag-day 0 to 1.04 (95% CI 0.94, 1.16) and 1.03 (95% CI 0.93, 1.14) for lag-day 0–1 (cumulative) and lag-day 1 (non-cumulative), respectively. For all-cause mortality, cumulative exposure to PM2.5 for lag-day 0–7 (1.07, 95% CI 1.00, 1.15) and non-cumulative exposure to NO2 at lag-day 6 (1.02, 95% CI 1.00, 1.03) were significant. Exposure to PM10 (per 10 μg/m3) was significantly associated with respiratory mortality at several lag-days. Adjusting for Ramadan did not significantly affect the results. PM10 had significant associations with respiratory mortality of people > 65 years old, and men for several lag-days. For IHD, NO2 affected older people, and men and women over different lag-days. Results of multi-pollutant models were similar to the single-pollutant model outcomes. In conclusion, NO2 and PM10 had more significant relationships with adverse health outcomes than the other pollutants.