Associations Between Ambient Nitrogen Dioxide and Daily Cause-specific Mortality

Background: There has been a long history of debate regarding whether ambient nitrogen dioxide (NO 2 ) directly affects human health. Methods: We conducted a nationwide time-series analysis in 272 major Chinese cities (2013–2015) to evaluate the associations between short-term exposure to NO 2 and cause-specific mortality. We used the overdispersed generalized linear model together with the Bayesian hierarchical model to estimate the associations between NO 2 and mortality at the national and regional levels. We examined two-pollutant models with adjustment of fine particles, sulfur dioxide, carbon monoxide, and ozone to evaluate robustness for the effects of NO 2 . Results: At the national-average level, we observed linear and positive associations between NO 2 and mortality from all causes and main cardiorespiratory diseases. A 10 μg/m 3 increase in 2-day average concentrations of NO 2 would lead to increments of 0.9% (95% posterial interval [PI], 0.7%, 1.1%) in mortality from total nonaccidental causes, 0.9% (95% PI, 0.7%, 1.2%) from total cardiovascular disease, 1.4% (95% PI, 0.8%, 2.0%) from hypertension, 0.9% (95% PI, 0.6%, 1.2%) from coronary heart disease, 0.9% (95% PI, 0.5%, 1.2%) from stroke, 1.2% (95% PI, 0.9%, 1.5%) from total respiratory diseases, and 1.6% (95% PI, 1.1%, 2.0%) from chronic obstructive pulmonary disease. There were no appreciable differences in estimates from single-pollutant and two-pollutant models. The associations were stronger in the south of China, in the elderly, and in females. Conclusions: The present study provided robust epidemiologic evidence of associations between day-to-day NO 2 and mortality from total natural causes and main cardiorespiratory diseases that might be independent of other criteria air pollutants.