[en] Aggressive emission control measures were taken by the Chinese government after the promulgation of the ‘Air Pollution Prevention and Control Action Plan’ in 2013. Here we evaluated the air quality and health benefits associated with this stringent policy during 2013–2015 by using surface PM_2.5 concentrations estimated from a three-stage data fusion model and cause-specific integrated exposure–response functions. The population-weighted annual mean PM_2.5 concentrations decreased by 21.5% over China during 2013–2015, reducing from 60.5 in 2013 to 47.5 μg m⁻³ in 2015. Subsequently, the national PM_2.5-attributable mortality decreased from 1.22 million (95% CI: 1.05, 1.37) in 2013 to 1.10 million (95% CI: 0.95, 1.25) in 2015, which is a 9.1% reduction. The limited health benefits compared to air quality improvements are mainly due to the supralinear responses of mortality to PM_2.5 over the high concentration end of the concentration–response functions. Our study affirms the effectiveness of China’s recent air quality policy; however, due to the nonlinear responses of mortality to PM_2.5 variations, current policies should remain in place and more stringent measures should be implemented to protect public health. (letter)

[en] Following a series of extreme air pollution events, the Chinese government released the Air Pollution Prevention and Control Action Plan in 2013 (China’s State Council 2013). The Action Plan sets clear goals for key regions (i.e. cities above the prefecture level, Beijing-Tianjin-Hebei Province, the Yangtze River Delta and the Pearl River Delta) and establishes near-term control efforts for the next five years. However, the extent to which the Action Plan can direct local governments’ activities on air pollution control remains unknown. Here we seek to evaluate the air quality improvement and associated health benefits achievable under the Action Plan in the Pearl River Delta (PRD) area from 2012 to 2017. Measure-by-measure quantification results show that the Action Plan would promise effective emissions reductions of 34% of SO_2, 28% of NO_x, 26% of PM_2_._5 (particulate matter less than 2.5 μm in diameter), and 10% of VOCs (volatile organic compounds). These emissions abatements would lower the PM_2_._5 concentration by 17%, surpassing the 15% target established in the Action Plan, thereby avoiding more than 2900 deaths and 4300 hospital admissions annually. We expect the implementation of the Action Plan in the PRD would be productive; the anticipated impacts, however, fall short of the goal of protecting the health of local residents, as there are still more than 33 million people living in places where the annual mean ambient PM_2_._5 concentrations are greater than 35 μg m"−"3, the interim target-3 of the World Health Organization (WHO). We therefore propose the next steps for air pollution control that are important not only for the PRD but also for all other regions of China as they develop and implement effective air pollution control policies. (letter)

[en] Facing severe air pollution issues, China has implemented a series of clean air policies aimed to improve the country’s air quality. These policies largely focused on reducing emissions of major air pollutants such as sulfur dioxide (SO₂) and primary aerosols. However, changes in such pollution also affect radiative forcing. To understand the climate consequences of these clean air actions in China, we evaluate the near-equilibrium climate response to sustained changes in aerosol (and precursors) emission rates equivalent to those that occurred in China between 2006 and 2017. During this period, China’s SO₂ emissions declined by ∼70%, and black carbon emissions declined by ∼30%. Climate simulations that used a fully coupled ocean and atmosphere climate model indicate that China’s reductions in aerosol emission rates from 2006 to 2017 may exert a net increase in global radiative forcing of 0.09 ± 0.03 W m⁻² and a mean warming of 0.12 ± 0.01 °C in the Northern Hemisphere; and may also affect the precipitation rates in East Asia and in more distant regions. The success of Chinese policies to further reduce aerosol emissions may bring additional net warming, and this ‘unmasked’ warming would in turn compound the challenge and urgency of international climate mitigation efforts. (letter)

[en] Tropospheric nitrogen dioxide (NO₂) column densities detected from space are widely used to infer trends in terrestrial nitrogen oxide (NO _x ) emissions. We study changes in NO₂ column densities using the Ozone Monitoring Instrument (OMI) over China from 2005 to 2015 and compare them with the bottom-up inventory to examine NO _x emission trends and their driving forces. From OMI measurements we detect the peak of NO₂ column densities at a national level in the year 2011, with average NO₂ column densities deceasing by 32% from 2011 to 2015 and corresponding to a simultaneous decline of 21% in bottom-up emission estimates. A significant variation in the peak year of NO₂ column densities over regions is observed. Because of the reasonable agreement between the peak year of NO₂ columns and the start of deployment of denitration devices, we conclude that power plants are the primary contributor to the NO₂ decline, which is further supported by the emission reduction of 56% from the power sector in the bottom-up emission inventory associated with the penetration of selective catalytic reduction (SCR) increasing from 18% to 86% during 2011–2015. Meanwhile, regulations for vehicles also make a significant contribution to NO _x emission reductions, in particular for a few urbanized regions (e.g., Beijing and Shanghai), where they implemented strict regulations for vehicle emissions years before the national schedule for SCR installations and thus reached their NO₂ peak 2–3 years ahead of the deployment of denitration devices for power plants. (letter)

[en] Highlights: • Probability distribution of ozone-related stroke susceptibility remained unknown. • We included a representative sample of 1,292,010 Chinese adults nationwide. • We explored 14 individual-level potential modifiers of ozone-stroke associations. • Susceptibility to ozone-related stroke varied largely among the entire population. • Acute effects of ozone on stroke were significant only in specific subpopulations. -- Abstract: Evidence suggesting an association between ozone exposure and stroke risk remains inconsistent; variations in the distributions of susceptibilities of the study populations may explain some of it. We examined the hypothesis in a general Chinese population. During 2013–2015, 1356 first-ever stroke events were selected from a large representative sample, the China National Stroke Screening Survey (CNSSS) database; daily maximal 8-hour ozone concentrations were obtained from spatiotemporally interpolated estimates of in-situ observations over China. We conducted a time-stratified case-crossover design to assess associations between stroke risk and ambient ozone exposure. Next, potential effect modifiers were identified using interaction analyses. Final, a well-established approach was applied to estimate individual-level susceptibility (i.e., the individual-specific effect given a certain combination of multiple effect-modifiers) and its probability distribution among all the CNSSS participants (n = 1,292,010). With adjustments for temperature, relative humidity and ambient fine particulate matter exposure, a 10-μg/m³ increment in mean ozone levels 2–3 day prior to symptom onset was associated with a 3.0% change in stroke risk (95% confidence interval: −1.2%, 7.3%). This association was statistically significantly enhanced by male gender, rural residence and low vegetable and fruit consumption. The subgroup results suggested that a fraction of the population might be considerably affected by ozone, regardless of the insignificant association in average level. The analysis of susceptibility distribution further indicated that the ozone-stroke association was statistically significantly positive in 14% of the general population. Susceptibility to ozone-related stroke significantly varied among Chinese adults. Characterizing individual-level susceptibility reveals the complexity underlying the weak average effect of ozone, and supports to plan subpopulation-specific interventions to mitigate the stroke risk.

[en] Coal-fired power plants (CPPs) dominate China’s energy supply systems. Over the past two decades, the explosive growth of CPPs has led to negative air quality and health impacts in China, and a series of control policies have been implemented to alleviate those impacts. In this work, by combining a CPPs emission database over China (CPED), a regional chemical transport model (WRF-CMAQ), and the integrated exposure-response model, we summarized historical and ongoing emission control policies on CPPs over China, investigated the air quality and health impacts of China’s CPPs during 2005–2020, and quantified the benefits of each policy. We found that despite the 97.4% growth of coal-fired power generation during 2005–2015, PM_2.5 exposures caused by emissions from China’s CPPs decreased from 9.0 μg m⁻³ in 2005 to 3.6 μg m⁻³ in 2015. The active emission control policies have decreased CPPs-induced PM_2.5 exposures by 10.0 μg m⁻³ during 2005–2015. We estimated that upgrading end-of-pipe control facilities and early retirement of small and low-efficiency units could respectively reduce PM_2.5 exposures by 7.9 and 2.1 μg m⁻³ during 2005–2015 and avoid 111 900 and 31 400 annual premature deaths. Since 2015, China’s government has further required all CPPs to comply with the so-called ‘ultra-low emission standards’ before 2020 as a major component of China’s clean air actions. If the policy is fully deployed, CPPs-induced PM_2.5 exposures could further decrease by 2.5 μg m⁻³ and avoid 43 500 premature deaths annually. Our study confirms the effectiveness of tailored control policies for China’s CPPs and reveals that those policies have played important roles in air quality improvement in China. (letter)

[en] Highlights: • The air quality cobenefits of achieving China's carbon neutrality before 2060 was quantitatively investigated. • This study proposed a mid-to-long-term air quality improvement pathway until 2060 of China (CAEP-CAP). • End-of-pipe controls can greatly improve air quality before 2035, while low-carbon policy will be more critical after 2035. Achieving carbon neutrality before 2060 newly announced in China are expected to substantially affect air quality. Here we project the pollutants emissions in China based on a carbon neutrality roadmap and clean air policies evolution; national and regional PM_2.5 and O₃ concentrations in 2030 (the target year of carbon peak), 2035 (the target year of “Beautiful China 2035” launched by the Chinese government to fundamentally improve air quality) and 2060 (the target year of carbon neutrality) are then simulated using an air quality model. Results showed that compared with 2019, emissions of SO₂, NO_x, primary PM_2.5, and VOCs are projected to reduce by 42%, 42%, 44%, and 28% in 2030, by 57%, 58%, 60%, and 42% in 2035, by 93%, 93%, 90% and 61% in 2060 respectively. Consequently, in 2030, 2035, and 2060, the national annual mean PM_2.5 will be 27, 23, and 11 μg m⁻³; and the 90th percentile of daily 8-h maxima of O₃ (O₃-8h 90th) will be 129, 123, and 93 μg m⁻³; 82%, 94%, and 100% of 337 municipal cities will reach the current national air quality standard, respectively. It's expected that the “Beautiful China 2035” target is very likely to be achieved, and about half of the 337 cities will meet the current WHO air quality guideline in 2060. In the near future, strict environmental policies driven by “Beautiful China 2035” are needed due to their substantial contribution to emission reductions. By 2060, the low-carbon policies driven by the carbon neutrality target are expected to contribute to larger than 80% of reductions in PM_2.5 and O₃-8h 90th concentrations relative to the 2020 levels, implying that more attention could be paid to low-carbon policies after 2035. Our research would provide implications for future co-governance of air pollution and climate change mitigation in China and other developing countries.

[en] High resolution pollution maps are critical to understand the exposure and health effect of local residents to air pollution. Currently, none of the single technologies used to measure or estimate concentrations of pollutants can provide sufficient resolved exposure data. Land use regression (LUR) models were developed to combine ground-based measurements, satellite remote sensing (SRS) and air quality model (AQM), together with geographic and local source related spatial inputs, to generate high resolution pollution maps for both PM_2.5 and NO₂ in Pearl River Delta (PRD), China. Four sets of LUR models (LUR without SRS or AQM, with SRS only, with AQM only, and with both SRS and AQM), all including local traffic emissions and land use variables, were compared to evaluate the contribution of SRS and AQM data to the performance of LUR models in PRD region. For NO₂, the annual model with SRS estimate performed best, explaining 60.5% of the spatial variation. For PM_2.5, the annual model with traditional predictor variables without SRS or AQM estimates showed the best performance, explaining 88.4% of the spatial variation. Pollution surfaces at 200 m*200 m resolution were generated according to the best performed models. - Highlights: • Provide high resolution pollution surface for PM_2.5 and NO₂ in Pearl River Delta. • Incorporate remote sensing and air quality model estimates in land use regression. • Evaluate performance of traffic emission inventory in land use regression models. • Provide essential inputs for exposure and health research. - This research provided high resolution pollution surface for PM_2.5 and NO₂ by incorporating remote sensing and air quality model estimates in land use regression.

[en] Highlights: • Solid fuel consumption rises with the increase in Heating Degree Days. • A transition from biofuel to coal occurs with per capita income growth. • Estimated coal consumption is 62% higher than that reported in official statistics. • An improved emission inventory of the residential sector is built in China. • Our work provides a new approach of obtaining data for other developing countries. -- Abstract: Solid fuel consumption and associated emissions from residential use are highly uncertain due to a lack of reliable statistics. In this study, we estimate solid fuel consumption and emissions from the rural residential sector in China by using data collected from a new nationwide field survey. We conducted a field survey in 2010 which covered ∼17,000 rural residential households in 183 counties in China, to obtain data for solid fuel consumption and use patterns. We then developed a Generalized Additive Model (GAM) to establish the relationship between solid fuel consumption and heating degree days (HDD), income, coal production, coal price, and vegetation coverage, respectively. The GAM was used to estimate solid fuel consumption in rural households in China at the county level. We estimated that, in 2010, 179.8Tg of coal were consumed in Chinese rural households for heating and cooking, which is 62% higher than that reported in official energy statistics. We found that large quantities of rural residential coal consumption in the North China Plain were underreported in energy statistics. For instance, estimated coal consumption in rural households in Hebei (one of most polluted provinces in China) was 20.8Tg in 2010, which is twice as high as government statistics indicate. In contrast, modeled national total consumption of crop residues (used as fuels) we found to be ∼50% lower than reported data. Combining the underlying data from the survey, the GAM and emission factors from literature, we estimate emissions from China’s rural residential sector in 2010 to be: 3.3Tg PM_2.5, 0.6Tg BC, 1.2Tg OC, 2.1Tg VOC, 2.3Tg SO₂, 0.4Tg NOx, 43.6Tg CO and 727.2Tg CO₂, contributing to 29%, 35%, 38% and 26% of national total PM_2.5, BC, OC, and CO emissions respectively. This work reveals that current emission inventories in China likely underestimate emissions from coal combustion in rural residential households due to missing coal consumption in official statistics, especially for the heavily polluted North China Plain (NCP) region. Per capita income appears to be the driving factor that results in the difference between surveyed data and official data. Residents with high income prefer commercial energy and have a higher per capita fuel consumption than lower income residents. Therefore, rural residential coal combustion may contribute even more to regional air pollution than the large contributions previously identified.

[en] Four haze episodes (EPs) were observed in October 2014 in Beijing, China. For better understanding of the characteristics and the formation mechanisms of PM_2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 μm), especially secondary water-soluble inorganic species in these haze events, hourly concentrations of PM_2.5, sulfate, nitrate, and ammonium (SNA) were measured in this study. Concentrations of gaseous pollutants and meteorological parameters were also measured. The average concentration of PM_2.5 was 106.6 ± 83.5 μg m⁻³, which accounted for around 53% of PM₁₀ (particulate matter with an aerodynamic diameter ≤ 10 μm) mass. Nitrogen dioxide (NO₂) concentration was much higher than that of sulfur dioxide (SO₂) since October is a non-heating month. SNA is the most abundant secondary water-soluble inorganic species and contributed to 33% of PM_2.5 mass concentration. Sulfur oxidation ratio (SOR) was much higher than nitrogen oxidation ratio (NOR). NOR and SOR increased with elevated PM_2.5 levels and heterogeneous processes seemed to be the most plausible explanation of this increase. Relative humidity (RH), which is of great influence on aerosol liquid water content (ALWC), played a considerable role in the formation of secondary inorganic aerosols, accelerated the secondary transformation of gaseous precursors, and further aggravated haze pollution. The positive feedback loop associated with high aerosol levels and low planetary boundary layer (PBL) height led to the evolution and exacerbation of heavy haze pollution. Fire maps and 48-h air mass backward trajectories supported the significant impact of biomass burning activities and regional transport on haze formation over Beijing in October 2014. - Highlights: • SO₄^2-, NO₃⁻, NH₄⁺ together accounted for about 32% of the total PM_2.5 mass. • NOR and SOR increased along with PM_2.5 concentrations during severe haze periods. • Meteorological factors played an important role in the formation of haze events. • High RH, low wind speed, and low PBL height aggravated the haze pollution. • Biomass burning from regional transport affected the haze formation. - Heavy haze often occurred in autumn in North China, which has not drawn enough attention. Both photochemical and heterogeneous reactions contributed to the secondary transformation of pollutants.