Oxidative potential of atmospheric fine particles in China from 2013 to 2023: trends, drivers, and mitigation implications

The ambient fine particle (PM_2.5) pollution in China has declined over the past decade, as a consequence of stringent clean air actions from 2013 to 2023. The sustained policy interventions have not only reduced the magnitude of PM_2.5 concentrations but also reshaped the source profile, i.e., the contribution from different emission sources. PM_2.5 toxicity varies markedly across emission sources, complicating the identification of dominant contributors and the robust quantification of associated health risks. The existing health risk assessments tend to rely primarily on PM_2.5 mass concentrations and therefore neglect toxicity differences by emission source. By contrast, oxidative potential (OP), which reflects the capacity of particles to induce oxidative stress, may provide a more mechanistically grounded metric for toxicity assessment. Here, we developed a method to estimate the OP of PM_2.5 in China, integrating direct ambient sample measurements with the GEOS-Chem model simulations and satellite observations, enabling nationwide, long-term reconstruction of aerosol toxicity at high spatiotemporal resolution. Using population-weighted mean exposure estimate (i.e., PWM-PM_2.5 concentrations and PWM-OP) as the exposure metric, we systematically track the evolution of PM_2.5 toxicity across China under policy-driven changes in emission sources and air pollution situations. The preliminary results show that, PWM-PM_2.5 between 2013 and 2023 declined from 62.8 to 33.9 μg m^-3 (−46%). Over the same period, PWM-OP declined from 2.48 to 1.17 nmol min^-1 m^-3 (−53%). Reductions were primarily attributed to control of coal combustion, underscoring the importance of energy-structure transitions and pollution control in reducing population health risks. In contrast, meteorological variability exerted a comparatively minor influence on these improvements; over 2013-2023, meteorological changes increased PWM-PM_2.5 by 0.4 μg m^-3 and PWM-OP by 0.62 nmol min^-1 m^-3, only partially offsetting the benefits of emission reductions. Our findings suggest that air quality improvements cannot be understood solely through PM_2.5 mass concentrations and that toxicity metrics can offer additional insights relevant to health. The future clean air policies need to shift from concentration-oriented targets to toxicity-oriented emission source control strategies, prioritizing the reduction of high-risk sources to achieve great health benefits.

 

Keywords: PM_2.5; Oxidative potential; Policy-driven; Coal combustion; Health benefits