The Associations of Short-Term Ambient Nitrogen Dioxide Pollution with Major Cause-Specific Morbidities and the Modifying Effects by Ambient Temperature: A Nationwide Case-Crossover Study

Consistent evidence linking short-term ambient nitrogen dioxide (NO₂) exposure to cause-specific morbidities is limited to asthma, and the modifying effect by ambient temperature is unclear in the context of climate change. This two-stage time-stratified case-crossover study investigated the morbidity risks and burden of short-term NO₂ exposure on major cause-specific hospital admissions (HAs) for respiratory diseases (RDs), cardiovascular diseases (CVDs), and kidney diseases in 291 Chinese cities of prefecture-level or above during 2013-2017, based on 47,182,205 HA records. For each 10 μg/m³ increase in NO₂ at lag01, the overall percent changes in HAs ranged from 1.15% for asthma to 3.28% for chronic renal failure. Compared to NO₂ concentrations <25 μg/m³, excess risks in HAs associated with exposure to NO₂ concentrations ≥25 μg/m³ at lag01 ranged from 2.14% (acute coronary syndrome, ACS) to 4.56% (acute bronchitis). Total attributable fractions associated with short-term NO₂ exposure ranged from 2.01% for ACS to 4.82% for chronic renal failure. Associations of NO₂ with major cause-specific HAs were generally stronger at a low temperature than at a high temperature. These findings suggest that more stringent NO₂ quality guidelines and regulations are needed in the context of climate change to generate additional health benefits.