Accounting for the Health Benefits of Air Pollution Regulations in China, 2008-2019

China launched ambitious air pollution regulations in 2013 that have resulted in substantial reductions in concentrations of particulate matter with aerodynamic diameters of 2.5 micrometers or less (PM_2.5). The main objective of this project is to analyze whether regulations to control PM_2.5 have been associated with declining mortality rates, especially in locations where the regulations caused larger reductions in PM_2.5 concentrations. In addressing this main objective, we control for ozone (O₃) concentrations. In addition, we examine and analyze available PM_2.5 components (that is, the subspecies that make up PM_2.5) and related air pollutants in secondary analyses that focused on understanding the influence of specific source sectors and emission control policies on PM_2.5 trends.

We used both observations and model outputs to characterize observed and counterfactual spatiotemporal trends in air quality from 2008 to 2019 across China. We characterized observed PM_2.5 and O₃ concentrations from 2008 to 2019 across China using published gridded datasets that incorporate observations along with remote sensing and other data to estimate surface concentrations that are spatially and temporally complete. We used the Community Multiscale Air Quality (CMAQ) model to both reproduce observed pollution and to simulate concentrations of PM_2.5 and O₃ that would have occurred absent regulations from 2008 to 2019. Additional CMAQ scenarios quantified the impacts of a range of source-specific emission control policies on ambient concentrations. In a secondary, supporting analysis, we analyzed observed speciated particulate matter data from three cities using source apportionment methods to infer changes in pollution source influences over time. We analyzed mortality data from two large, representative cohorts maintained by the Chinese Center for Disease Control and Prevention in relation to spatial and temporal variations in PM_2.5 and O₃ concentrations using two methods. We first analyzed the health data using a traditional Cox proportional hazards model to estimate conventional hazard ratios (HR) for PM_2.5 risk. Next, we implemented novel causal methods based on principal stratification to analyze the extent to which regulatory policies implemented starting in 2013 were associated with reduced mortality across China.

From 2013 to 2019, we estimate there was a ~45% reduction in PM_2.5 as compared to a no-control scenario, but with considerable regional heterogeneity. Associations were observed between PM_2.5 and mortality rates in all cohorts, though results were sensitive to model specification in a cohort of elderly subjects. Results of causal models suggested that improvements in PM_2.5 since 2013 were associated with increased survival probability in both cohorts.

The scope of air pollution regulations and resulting PM_2.5 improvements in China since 2013 provided a unique opportunity for accountability research. Our study provides evidence supporting the health benefits of those policies.