Prioritizing Urban Emission Reductions to Mitigate Pollution and Health Effects of Ozone and Nitrogen Dioxide in China

Despite significant reductions in fine particulate matter (PM_2.5) concentrations in China due to air pollution control measures, ozone (O₃) pollution has worsened in recent years, with pronounced regional disparities in long-term exposure to O₃ and NO₂. Assessing these disparities in exposure to gaseous pollutants and the resulting unequal health risks between urban and rural regions has become increasingly essential. The contributions of various anthropogenic emissions to O₃ and NO₂ were quantified using a source-oriented version of the Community Multiscale Air Quality (CMAQ) model, combined with population and GDP data sets. From 2010 to 2019, NOx and VOC emissions from non-urban areas decreased by 14% and 25%, respectively, whereas urban anthropogenic activities caused a 10% increase in NOx emissions and a 22% rise in VOC emissions. The simulations indicated that background levels constituted the majority of maximum daily 8-hr average O₃ (MDA8 O₃), contributing 83% in 2010 and 75% in 2019. Non-urban anthropogenic activities were the primary sources of NO₂, accounting for 64% in 2010 and 57% in 2019. The proportion of O₃ and NO₂ from urban anthropogenic emissions in the total concentration continuously increased between 2010 and 2019. Although overall O₃-related premature mortality increased by 51% and NO₂-related premature mortality decreased by 3% during this period, the number of premature mortalities related to O₃ and NO₂ from urban anthropogenic activities rose by 133% and 15% respectively. We underscore the critical need to prioritize the reduction of urban anthropogenic emissions to effectively mitigate O₃ and NO₂ pollution in China.