Over 1 million people die every year from diseases caused by exposure to outdoor PM_2·5 air pollution. As air pollutants and carbon dioxide are of the same origin, all mainly coming from the combustion and utilization of fossil fuels, in addition to clean-air policies that target pollution emissions, climate policies aimed at reducing fossil-fuel CO₂ emissions might also reduce the discharge of air pollutants and thus improve air quality and public health. Many studies by far have measured the changes of air pollution and environmental health benefits under different policy scenarios in China in the future, including the health benefits of current and future air pollution prevention policies, and the health co-benefits of various climate control policy scenarios. However, it is still unknown whether relying solely on climate control policies or end-treatment policies can continuously improve air quality and protect people's health and what kind of policies can be implemented to reduce the health loss caused by air pollution given the trend of the aging population putting forward higher requirements for air quality in the future.

To address the above problems, Zhang Qiang's Research Group and Tong Dan’s Research Group of the Department of Earth System Science (DESS), Tsinghua University have, based on the Dynamic Projection model for Emissions in China (DPEC) independently developed, constructed a policy scenario matrix that included 18 scenarios spanning a range of global climate targets (1·5°C, 2°C, national determined contributions [NDC], unambitious, baseline, and 4·5°C) as well as end-of-pipe controls: 2015-pollution, current-pollution, and ambitious-pollution. On this basis, the atmospheric chemistry model and health effect model were further coupled, to realize a comprehensive assessment of the future air quality changes and their health impacts in China under various pollution and carbon reduction pathways.

The outcome of the above research was published online in The Lancet Planetary Health in a paper titled “Role of climate goals and clean-air policies on reducing future air pollution deaths in China: a modelling study”. Based on a self-developed emission prediction model, the research team constructed 18 scenarios of climate control and air pollution control policies with different strengths. The future changes of PM_2.5 pollution exposure level in China under various scenarios were simulated, and the related health losses were calculated. It was pointed out that the synergizing pollution reduction and carbon reduction was the only way to reduce the health losses of air pollution in China. It was found that against the backdrops of population aging, the vulnerability risk of Chinese people to air pollution exposure continues to increase. Only by combining strict climate control policies with air pollution control policies and giving full play to the synergistic effect of pollution reduction and carbon reduction would the negative impact of population aging be offset, the health losses caused by air pollution continue to decrease, and people's health be effectively protected.

The research shows that the implementation of climate control policy or end-of-pipe control policy alone can promote further improvement of air quality. In all the 18 scenarios, except for the four scenarios composed of the pollution control level scenario in the base year and different climate control scenarios, the PM_2.5 pollution exposure level in the remaining 14 scenarios in 2015-2030 has obviously decreased (with a decrease > 5%). In 2030-2050, the exposure level of PM_2.5 pollution in all 18 scenarios decreased significantly, with a decrease of 8.2-54.8%. Under the most stringent coordination scenario of climate control and pollution control policies (1.5-degree temperature rise plus end-of-pipe control), the population-weighted PM_2.5 concentration in China would drop to 9.0 μ g/m3 in 2050, reaching the fourth stage goal of the World Health Organization (WHO).

However, due to the increasing vulnerability of people to air pollution under the background of population aging in the future, the improvement of air quality may not necessarily reduce the health losses caused by air pollution and continuously protect people's health. From the perspective of health protection, the improvement of air quality in most scenarios cannot offset the negative impact of aging. From 2015 to 2030, only four strict cooperative scenarios of pollution reduction and carbon reduction can significantly reduce premature PM_2.5-related deaths (with a decrease of > 5%); However, only the two most stringent synergistic scenarios of pollution reduction and carbon reduction (2-degree temperature rise plus enhanced end-of-pipe treatment and 1.5-degree temperature rise plus enhanced end-of-pipe treatment) could significantly reduce PM_2.5-related deaths from 2030 to 2050.

By combining climate control and air pollution control policies with different strengths, the scenario matrix of synergized emission reduction of pollution and carbon reduction was constructed, and the future air quality changes and health impacts in China under various possible emission reduction paths were comprehensively evaluated. It is pointed out that only by implementing the strictest climate control and pollution control policies in coordination can people's health be continuously protected. From the perspective of health research, the importance of coordinated treatment of pollution reduction and carbon reduction against the backdrops of an aging population is underscored, and it is pointed out that health protection should be taken as the starting point of coordinated treatment of climate change and air pollution, and the synergization of pollution reduction and carbon reduction should be promoted. The research results provide a scientific basis for to formulate a road map for coordinated governance of pollution reduction and carbon reduction against the backdrops of China's carbon peaking and carbon neutrality, while providing a useful reference for other developing countries facing similar climate and environmental problems to formulate coordinated governance strategies.

Liu Yang, a doctoral candidate of DESS, Tsinghua University, and Assistant Professor Tong Dan are the co-first authors of the paper; Professor Zhang Qiang is the corresponding author of the paper. The collaborators include Dr. Cheng Jing, Department of Earth Science System, Tsinghua University; Professor Steven J. Davis, University of California, Irvine; Dr. Yu Sha and Dr. Brinda Yarlagadda, Joint Global Change Research Institute, Pacific Northwest National Laboratory; Professor Leon E. Clarke, Center for Global Sustainability, the University of Maryland, USA; Professor Michael Brauer, School of Population and Public Health, the University of British Columbia, Professor Aaron J. Cohen, Health Effects Institute, Boston, MA, USA, Professor Kan Haidong, School of Public Health, Fudan University, and Xue Tao, Associate Research Fellow, School of Public Health, Peking University Health Science Centre. The research was supported by the National Natural Science Foundation of China.

Figure PM_2.5 exposure and changes in PM_2.5-related premature deaths across all ranges of climate targets and stringency of pollution controls in 2030 and 2050

(A) Population-weighted PM_2.5 concentrations. (B) PM_2.5-related premature deaths. (C) PM_2.5 concentration changes during 2015–30 and 2030–50 compared with 53·1 μg/m3 population-weighted PM_2.5 concentrations in 2015. (D) PM_2.5-related premature death changes during 2015–30 and 2030–50.

Full-text link:

https://www.sciencedirect.com/science/article/pii/S2542519621003260

Written by Zhang Qiang

Edited by Wang Jiayin

Reviewed by Zhang Qiang