The Long Hazy Tail: Analysis of the Impacts and Trends of Severe Outdoor and Indoor Air Pollution in North China.

China, especially the densely populated North China region, experienced severe haze events in the past decade that concerned the public. Although the most extreme cases have been largely eliminated through recent mitigation measures, severe outdoor air pollution persists and its environmental impact needs to be understood. Severe indoor pollution draws less public attention due to the short visible distance indoors, but its public health impacts cannot be ignored. Herein, we assess the trends and impacts of severe outdoor and indoor air pollution in North China from 2014 to 2021. Our results demonstrate the uneven contribution of severe hazy days to ambient and exposure concentrations of particulate matter with an aerodynamic diameter <2.5 (PM2.5). Although severe indoor pollution contributes to indoor PM2.5 concentrations (23%) to a similar extent as severe haze contributes to ambient PM2.5 concentrations (21%), the former's contribution to premature deaths was significantly higher. Furthermore, residential emissions contributed more in the higher PM2.5 concentration range both indoors and outdoors. Notably, severe haze had greater health impacts on urban residents, while severe indoor pollution was more impactful in rural areas. Our findings suggest that, besides reducing severe haze, mitigating severe indoor pollution is an important aspect of combating air pollution, especially toward improving public health.

An optimized denoising method for ICESat-2 photon-counting data considering heterogeneous density and weak connectivity.

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) can obtain underwater elevation due to its strong penetration ability. However, the photons recorded by ICESat-2 include a large amount of noise that needs to be removed. Although density-based clustering methods can finish signal photon extraction, heterogeneous density and weak connectivity in photon data distribution impede their denoising performance, especially for sparse signals in deep water and drastic topographic change areas. In this paper, a novel fused denoising method based on the local outlier factor and inverse distance metric is proposed to overcome the above problems. The local outlier factor and inverse distance metric are calculated based on K-nearest neighbors (KNNs), taking into account not only the difference in density but also the directional uniformity of the data distribution. Using six trajectories under various seabed topographies, the proposed method is compared with state-of-the-art ICESat-2 photon denoising algorithms and official ATL03 results. The results indicate that the overall accuracy of the proposed method can surpass 96%, and the proposed method maintains higher recall but also has a lower false positive rate. Compared with the results of other methods, the proposed method can better adopt areas with abrupt topographic changes and deep water. The extracted signal strips are more unbroken and continuous. This study can contribute to pioneering a new perspective for ICESat-2 photon-counting data denoising research that is limited to using only density-based algorithms.

Drinking Water in Rural China: Water Sources, Treatment, and Boiling Energy.

Access to safe drinking water is a major public concern in China. A national survey of 57 029 households was conducted to fill major knowledge gaps on drinking water sources, end-of-use treatment methods, and energy used to boil water. Herein, we show that surface water and well water were frequently used by >147 million rural residents living in low-income inland and mountainous areas. Driven by socioeconomic development and government intervention, the level of access to tap water in rural China increased to 70% by 2017. Nevertheless, the rate was considerably lower than that in cities and unevenly distributed across the country. Approximately 90% of drinking water was boiled, an increase from 85% a decade ago. The contribution of electricity, mainly electric kettles, to the boiling of water was 69%. Similar to cooking, living conditions and heating requirements are the main influencing indicators of energy used to boil water. In addition to socioeconomic development, government intervention is a key factor driving the transition to safe water sources, universal access to tap water, and clean energy. Further improvement in drinking water safety in poor and remote rural areas remains challenging, and more intervention and more investment are needed.

Costs and Benefits of Household Fuel Policies and Alternative Strategies in the Jing-Jin-Ji Region.

Air pollution is still one of the most severe problems in northern China, especially in the Jing-Jin-Ji region around Beijing. In recent years, China has implemented many stringent policies to address the air quality issue, including promoting energy transition toward cleaner fuels in residential sectors. But until 2020, even in the Jing-Jin-Ji region, nearly half of the rural households still use solid fuels for heating. For residents who are not covered by the clean heating campaign, we analyze five potential mitigation strategies and evaluate their environmental effects as well as the associated health benefits and costs. We estimate that substitution with electricity or gas would reduce air pollution and premature mortality more strongly, while the relatively low investment costs of implementing clean coal or biomass pellet lead to a larger benefit-cost ratio, indicating higher cost efficiency. Hence, clean coal or biomass pellet could be transitional substitution options for the less developed or remote areas which cannot afford a total transition toward electricity or natural gas in the short term.

Significant but Inequitable Cost-Effective Benefits of a Clean Heating Campaign in Northern China.

Residential emissions significantly contribute to air pollution. To address this issue, a clean heating campaign was implemented to replace coal with electricity or natural gas among 13.9 million rural households in northern China. Despite great success, the cost-benefits and environmental equity of this campaign have never been fully investigated. Here, we modeled the environmental and health benefits, as well as the total costs of the campaign, and analyzed the inequality and inequity. We found that even though the campaign decreased only 1.1% of the total energy consumption, PM2.5 emissions and PM2.5 exposure experienced 20% and 36% reduction, respectively, revealing the amplification effects along the causal pathway. Furthermore, the number of premature deaths attributable to residential emissions reduced by 32%, suggesting that the campaign was highly beneficial. Governments and residents shared the cost of 2,520 RMB/household. However, the benefits and the costs were unevenly distributed, as the residents in mountainous areas were not only less benefited from the campaign but also paid more because of the higher costs, resulting in a notably lower cost-effectiveness. Moreover, villages in less developed areas tended to choose natural gas with a lower initial investment but a higher total cost (2,720 RMB/household) over electricity (2,190 RMB/household). With targeted investment and subsidies in less developed areas and the promotion of electricity and other less expensive alternatives, the multidevelopment goals of improved air quality, reduced health impacts, and reduced inequity in future clean heating interventions could be achieved.

Can the Tilburg Frailty Indicator predict post-operative quality of recovery in patients with gynecologic cancer? A prospective cohort study.

OBJECTIVE: Frailty is a marker of physiologic decline within multiple organ systems. The Tilburg Frailty Indicator (TFI) is an instrument for assessing frailty. We evaluated the ability of the TFI to predict the quality of post-operative recovery in patients with gynecologic cancer and explored the associations between frailty, post-operative complications, and length of stay. METHODS: We conducted a prospective cohort study of patients scheduled for radical gynecologic cancer surgery between May 2021 and January 2022, and defined a TFI score ≥5 as 'frailty'. Our primary outcome was the post-operative quality of recovery based on the Quality of Recovery-15 (QoR-15), and the secondary outcomes were post-operative complications and length of stay. Multiple logistic regression was used to examine the relationship between frailty and outcomes. We developed receiver operating characteristics (ROCs) and assessed areas under the ROC curves (AUCs) to explore the ability of frailty to predict the quality of post-operative recovery. RESULTS: A total of 169 patients were included. The prevalence of frailty using the TFI was 47.9% in this cohort. In the multivariate regression analysis, frailty emerged as a significant predictor of the 3-day QoR-15 score (aOR 11.69, 95% CI 4.26 to 32.08; p˂0.001) and complications (aOR 10.05, 95% CI 1.66 to 60.72; p=0.012). Frailty was not associated with length of stay (aOR 2.12, 95% CI 0.87 to 5.16; p=0.099). The combination of the TFI, American Society of Anesthesiologists (ASA) classification, and types of cancer resulted in an increase in the AUC compared with the TFI alone (AUC 0.796, 95% CI 0.727 to 0.865; p˂0.05). CONCLUSIONS: The use of the TFI may assist surgeons in estimating the risk with respect to post-operative quality of recovery and complications in patients with gynecologic cancer. Combining the TFI with ASA classification and cancer type is expected to improve the predictive ability of poor quality of recovery.

Source contributions and drivers of physiological and psychophysical cobenefits from major air pollution control actions in North China.

North China is among the most polluted regions in the country, and human exposure to PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 µm) in this region has led to severe health consequences. The region has also benefited the most from emission reductions in recent years. It is of interest to understand to what extent and through which paths emissions from different sectors cause adverse health impacts. Here, we present the results of a full evaluation of the health benefits of emission control actions implemented in recent years based on segregated emission inventories with an emphasis on residential emissions. Two major causal paths, one from residential emissions to indoor air pollution, exposure, and premature deaths, and the other from nonresidential emissions to ambient air pollution and psychophysical impacts, were identified and quantified. From 2014 to 2019, both ambient (33%) and indoor (39%) PM2.5 decreased significantly, leading to decreasing trends in exposure (36%), premature deaths (10%), and psychophysical impacts (21%). The Air Pollution Prevention and Control Action Plan, the Clean Heating Campaign, and spontaneous residential shifts to clean energy contributed significantly to these reductions when the effects of other drivers, such as population and economic growth, were excluded.

ICESat-2 laser data denoising algorithm based on a back propagation neural network.

The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) photon data is the emerging satellite-based LiDAR data, widely used in surveying and mapping due to its small photometric spot and high density. Since ICESat-2 data collect weak signals, it is difficult to denoise in shallow sea island areas, and the quality of the denoising method will directly affect the precision of bathymetry. This paper proposes a back propagation (BP) neural network-based denoising algorithm for the data characteristics of shallow island reef areas. First, a horizontal elliptical search area is constructed for the photons in the dataset. Suitable feature values are selected in the search area to train the BP neural network. Finally, data with a geographic location far apart, including daily and nightly data, are selected respectively for experiments to test the generality of the network. By comparing the results with the confidence labels provided in the official documents of the ATL03 dataset, the DBSCAN algorithm, and the manual visual interpretation, it is proved that the denoising algorithm proposed in this paper has a better processing effect in shallow island areas.

Remifentanil requirement for i-gel insertion is reduced in male patients with Parkinson's disease undergoing deep brain stimulator implantation: an up-and-down sequential allocation trial.

BACKGROUND: Laryngeal mask airways have been widely used in clinical practice. The aim of this study was to investigate whether the remifentanil requirement for facilitation of i-gel insertion in Parkinson's disease (PD) patients undergoing deep brain stimulation (DBS) surgery was different from that in non-PD (NPD) patients undergoing intracranial surgery. STUDY DESIGN: An up-and-down sequential allocation trial. METHODS: Male patients aged between 40 and 64 years old were enrolled. The first patient in each group (PD and NPD) group received an effect-site concentration (Ce) of remifentanil (Minto pharmacokinetic model) of 4.0 ng.ml-1 during a target-controlled infusion (TCI) of 3.5 µg.ml-1 propofol (Marsh pharmacokinetic model). The next dose of remifentanil was determined by the response of the previous patient. The Ce of remifentanil required for i-gel insertion in 50% of patients (EC50) was estimated by the modified Dixon's up-and-down method and by probit analysis. RESULTS: The PD group included 24 patients and the NPD group included 23. The EC50 of remifentanil for i-gel insertion during a TCI of 3.5 µg.ml-1 propofol estimated by the modified Dixon's up-and-down method in PD patients (2.38 ± 0.65 ng.ml-1) was significantly lower than in NPD patients (3.21 ± 0.49 ng.ml-1) (P = 0.03). From the probit analysis, the EC50 and EC95 (effective Ce in 95% of patients) of remifentanil were 1.95 (95% CI 1.52-2.36) ng.ml-1 and 3.12 (95% CI 2.53-5.84) ng.ml-1 in PD patients and 2.85 (95% CI 2.26-3.41) ng.ml-1 and 4.57 (95% CI 3.72-8.54) ng.ml-1 in NPD patients, respectively. CONCLUSIONS: The remifentanil requirement for successful i-gel insertion is reduced in male PD patients undergoing DBS implantation during propofol TCI induction. Clinicians should closely monitor the remifentanil requirement in patients with PD. TRIAL REGISTRATION: Registered at http://www.chictr.org.cn ( ChiCTR1900021760 ).

Energy and air pollution benefits of household fuel policies in northern China.

In addition to many recent actions taken to reduce emissions from energy production, industry, and transportation, a new campaign substituting residential solid fuels with electricity or natural gas has been launched in Beijing, Tianjin, and 26 other municipalities in northern China, aiming at solving severe ambient air pollution in the region. Quantitative analysis shows that the campaign can accelerate residential energy transition significantly, and if the planned target can be achieved, more than 60% of households are projected to remove solid fuels by 2021, compared with fewer than 20% without the campaign. Emissions of major air pollutants will be reduced substantially. With 60% substitution realized, emission of primary PM2.5 and contribution to ambient PM2.5 concentration in 2021 are projected to be 30% and 41% of those without the campaign. With 60% substitution, average indoor PM2.5 concentrations in living rooms in winter are projected to be reduced from 209 (190 to 230) µg/m3 to 125 (99 to 150) µg/m3 The population-weighted PM2.5 concentrations can be reduced from 140 µg/m3 in 2014 to 78 µg/m3 or 61 µg/m3 in 2021 given that 60% or 100% substitution can be accomplished. Although the original focus of the campaign was to address ambient air quality, exposure reduction comes more from improved indoor air quality because ∼90% of daily exposure of the rural population is attributable to indoor air pollution. Women benefit more than men.

GMSimpute: a generalized two-step Lasso approach to impute missing values in label-free mass spectrum analysis.

MOTIVATION: Missingness in label-free mass spectrometry is inherent to the technology. A computational approach to recover missing values in metabolomics and proteomics datasets is important. Most existing methods are designed under a particular assumption, either missing at random or under the detection limit. If the missing pattern deviates from the assumption, it may lead to biased results. Hence, we investigate the missing patterns in free mass spectrometry data and develop an omnibus approach GMSimpute, to allow effective imputation accommodating different missing patterns. RESULTS: Three proteomics datasets and one metabolomics dataset indicate missing values could be a mixture of abundance-dependent and abundance-independent missingness. We assess the performance of GMSimpute using simulated data (with a wide range of 80 missing patterns) and metabolomics data from the Cancer Genome Atlas breast cancer and clear cell renal cell carcinoma studies. Using Pearson correlation and normalized root mean square errors between the true and imputed abundance, we compare its performance to K-nearest neighbors' type approaches, Random Forest, GSimp, a model-based method implemented in DanteR and minimum values. The results indicate GMSimpute provides higher accuracy in imputation and exhibits stable performance across different missing patterns. In addition, GMSimpute is able to identify the features in downstream differential expression analysis with high accuracy when applied to the Cancer Genome Atlas datasets. AVAILABILITY AND IMPLEMENTATION: GMSimpute is on CRAN: https://cran.r-project.org/web/packages/GMSimpute/index.html. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Impact of preoperative transcatheter rectal arterial chemoembolization with concurrent chemoradiotherapy on surgery and prognosis of patients with locally advanced rectal cancer.

BACKGROUND AND OBJECTIVES: To analyze and evaluate the impact of preoperative transcatheter rectal arterial chemoembolization (TRACE) with concurrent chemoradiotherapy on surgery and prognosis of locally advanced rectal cancer (LARC). METHODS: A total of 118 patients with LARC were enrolled in this nonrandomized prospective study. They were assigned into the experimental group receiving preoperative TRACE with concurrent chemoradiotherapy (TRACE-CRT group, N = 60) and the control group receiving only neoadjuvant chemoradiotherapy (CRT group, N = 58). All patients underwent surgery after their preoperative treatments. RESULTS: All patients successfully completed the surgical operation. No significant differences were found in sphincter preservation rate and R0 resection rate between TRACE-CRT group and CRT group (p > 0.05). No significant differences were found between the two groups in terms of the perioperative indicators and postoperative complications except mean operation time (165.8 vs. 196.6 min, p < 0.001). Local recurrence occurred in 8 and 5 patients, respectively (p > 0.05). Distant metastasis occurred in 5 and 11 patients, respectively (p < 0.05). CONCLUSIONS: Adding TRACE in the preoperative standard treatment for LARC did not increase perioperative complications. In addition, it has the potential advantage of preventing distant metastasis. It is worthy of further application and promotion in clinical practice.

Synergistic Health Benefits of Household Stove Upgrading and Energy Switching in Rural China.

Rural residential energy switching from solid fuels to electricity and natural gas has resulted in substantial health benefits in China. Here, we quantitatively estimated the environmental and health benefits of stove upgrading, energy switching, and the interaction of stove upgrading and energy switching in rural mainland China during the period of 1980-2014. Driven by government intervention, technical progress, and socioeconomic development, domestic stoves have been upgraded from a domination of open-fire and traditional stoves to energy-saving, clean stoves, and gas range/electric stoves. Furthermore, stove upgrading significantly contributed to the overall reductions in PM2.5 emissions (25%), ambient and indoor PM2.5 concentrations (49 and 28%), population exposure (31%), and premature deaths (37%) attributable to residential emissions. The interaction between stove upgrading and energy switching resulted in an additional 15% reduction in premature deaths. The influences of the residential sector and the beneficial effects of stove upgrading and energy switching are magnified along the causal path from emissions to health impacts. The overall benefit of the transition in residential energy would be substantially underestimated without considering stove upgrading.

Updated Global Black Carbon Emissions from 1960 to 2017: Improvements, Trends, and Drivers.

Accurate estimation of black carbon (BC) emissions is essential for assessing the health and climate impact of this pollutant. Past emission inventories were associated with high uncertainty due to data limitations, and recent information has provided a unique updating opportunity. Moreover, understanding the drivers that cause temporal emission changes is of research value. Here, we update the global BC emission estimates using new data on the activities and emission factors (EFs). The new inventory covers 73 detailed sources at 0.1° × 0.1° spatial resolution and monthly temporal resolution from 1960 to 2017. The estimated annual emissions were 32% higher than the average of several previous inventories, which was primarily due to field-measured EFs for residential stoves and differentiated EFs for motor vehicles. In addition, the updated emissions show an inverse U-shaped temporal trend, which was mainly driven by the interaction between the positive effects of population growth, per capita energy consumption, and vehicle fleet and the negative effects of residential energy switching, stove upgrading, phasing out of beehive coke ovens, and reduced EFs for vehicles and industrial processes. Urbanization caused a significant increase in urban emissions accompanied by a more significant decline in rural emissions.

Direct and Inverse Reduced-Form Models for Reciprocal Calculation of BC Emissions and Atmospheric Concentrations.

Atmospheric black carbon (BC) concentrations are governed by both emissions and meteorological conditions. Distinguishing these effects enables quantification of the effectiveness of emission mitigation actions by excluding meteorological effects. Here, we develop reduced-form models in both direct (RFDMs) and inverse (RFIMs) modes to estimate ambient BC concentrations. The models were developed based on outputs from multiyear simulations under three conditional scenarios with realistic or fixed emissions and meteorological conditions. We established a set of probabilistic functions (PFs) to quantify the meteorological influences. A significant two-way linear relationship between multiyear annual emissions and mean ambient BC concentrations was revealed at the grid cell scale. The correlation between them was more significant at grid cells with high emission densities. The concentrations and emissions at a given grid cell are also significantly correlated with emissions and concentrations of the surrounding areas, respectively, although to a lesser extent. These dependences are anisotropic depending on the prevailing winds and source regions. The meteorologically induced variation at the monthly scale was significantly higher than that at the annual scale. Of the major meteorological parameters, wind vectors, temperature, and relative humidity were found to most significantly affect variation in ambient BC concentrations.

Coal Is Dirty, but Where It Is Burned Especially Matters.

Coal abatement actions for pollution reduction often target total coal consumption. The health impacts of coal uses, however, vary extensively among sectors. Here, we modeled the sectorial contributions of coal uses to emissions, outdoor and indoor PM2.5 (particulate matter with an aerodynamic diameter of less than 2.5 mm) concentrations, exposures, and health outcomes in China from 1970 to 2014. We show that in 2014, residential coal accounted for 2.9% of total energy use but 34% of premature deaths associated with PM2.5 exposure, showing that effects were magnified substantially along the causal path. The number of premature deaths attributed to unit coal consumption in the residential sector was 40 times higher than that in the power and industrial sectors. Emissions of primary PM2.5 were more important than secondary aerosol precursors in terms of health consequences, and indoor exposure accounted for 97% and 91% of total premature deaths attributable to PM2.5 from coal combustion in 1974 and 2014, respectively. Our assessment raises a critical challenge in the switching of residential coal uses to effectively mitigate PM2.5 exposure in the Chinese population.

Type of anesthesia and quality of recovery in male patients undergoing lumbar surgery: a randomized trial comparing propofol-remifentanil total i.v. anesthesia with sevoflurane anesthesia.

BACKGROUND: Previous studies have shown that women achieve a better quality of postoperative recovery from total intravenous anesthesia (TIVA) than from inhalation anesthesia, but the effect of anesthesia type on recovery in male patients is unclear. This study therefore compared patient recovery between males undergoing lumbar surgery who received TIVA and those who received sevoflurane anesthesia. METHODS: Eighty male patients undergoing elective one- or two-level primary transforaminal lumbar interbody fusion (TLIF) were randomly divided into two groups: the TIVA group (maintenance was achieved with propofol and remifentanil) or sevoflurane group (SEVO group: maintenance was achieved with sevoflurane and remifentanil). The quality of recovery-40 questionnaire (QoR-40) was administered before surgery and on postoperative days 1 and 2 (POD1 and POD2). Pain scores, postoperative nausea and vomiting, postoperative hospital stay, anesthesia consumption, and adverse effects were recorded. RESULTS: The QoR-40 scores were similar on the three points (Preoperative, POD1 and POD2). Pain scores were significantly lower in the SEVO group than in the TIVA group on POD1 (30.6 vs 31.4; P = 0.01) and POD2 (32 vs 33; P = 0.002). There was no significant difference in the postoperative hospital stay or complications in the postanesthesia care unit between the TIVA group and the SEVO group. CONCLUSIONS: This study demonstrates that the quality of recovery is not significantly different between male TLIF surgery patients who receive TIVA and those who receive sevoflurane anesthesia. Patients in the TIVA group had better postoperative analgesic effect on POD2. TRIAL REGISTRATION: This was registered at http://www.chictr.org.cn (registration number ChiCTR-IOR-16007987, registration date: 24/02/2016).

Differentiated-Rate Clean Heating Strategy with Superior Environmental and Health Benefits in Northern China.

Residential heating using solid fuels contributes significantly to air pollution and has subsequent health impacts in China. To mitigate emissions, a clean heating campaign (CHC-1) covering 28 municipalities has been implemented. Although only a single penetration rate was initially planned by CHC-1 for all municipalities, outcomes in the different municipalities varied considerably. Recently, a second phase (CHC-2) has been launched for the remaining 128 municipalities in northern China with once again a fixed penetration rate set. Here, we quantified factors that affected the penetration rates of CHC-1, developed an intervention scheme with differentiated targets for CHC-2, and compared the environmental and health benefits of the fixed- and differentiated-rate strategies. We found that the penetration rates of CHC-1 depended on per capita income, terrain slope, and population density and that such relationships could be quantified using a piecewise regression model. This model was applied to develop a differentiated-rate strategy for CHC-2. It clearly evidenced that a differentiated scheme would be more environmentally beneficial. Although the same number of rural households can achieve clean heating under both intervention scenarios, the proposed differentiated strategy can prevent 30 000 (23 000-34 000) premature deaths associated with residential heating annually compared to the 26 000 (21 000-31 000) premature deaths prevented under the fixed-rate scheme. Differences among gender and age groups and the effects of urbanization and aging are also discussed.

Stacked Use and Transition Trends of Rural Household Energy in Mainland China.

Household energy use is an important aspect of environmental pollution and sustainable development. From a nationwide residential energy survey, this study revealed that household fuel "stacking"-mixed use of multiple fuels-is becoming noticeable over the 20 years from 1992 to 2012, particularly in northern China where space heating is needed in the winter. Approximately 28% of rural households used only one single energy type in 1992, whereas the percentage declined to merely 11% in 2012. The number of energy types correlated positively with the heating degree days and negatively with the household income in areas with limited or no heating requirements. Combined use of biomass and fossil fuels may lead to extra energy use, up to 40% for cooking and 20% for heating. Some fuels, as supplementary ones, are used more often than others, and the energy consumption of coal and honeycomb briquette could be underestimated by 34% and 22% if only the primary energy was accounted for. Generally, household energy is shifting from solid fuels to cleaner ones, such as electricity or gas for both cooking and heating, but with different patterns and transition rates. Transition pathways varied extensively from one region to another due to the imbalanced development. Clean transitions initially occur in well-developed provinces and megacities and then extend to inland provinces approximately 5-10 years later. Rapid energy transitions and urbanization have led to nearly 50% reduction in residential energy consumption over these two decades, consequently resulting in significant declines in emissions of most air pollutants. The updated residential emission of primary PM2.5 was 3100 Gg in 2014. Extensively fuel stacking and rapid energy transitions have led to complex circumstances in energy use.

Distinguishing Emission-Associated Ambient Air PM2.5 Concentrations and Meteorological Factor-Induced Fluctuations.

Although PM2.5 (particulate matter with aerodynamic diameters less than 2.5 µm) in the air originates from emissions, its concentrations are often affected by confounding meteorological effects. Therefore, direct comparisons of PM2.5 concentrations made across two periods, which are commonly used by environmental protection administrations to measure the effectiveness of mitigation efforts, can be misleading. Here, we developed a two-step method to distinguish the significance of emissions and meteorological factors and assess the effectiveness of emission mitigation efforts. We modeled ambient PM2.5 concentrations from 1980 to 2014 based on three conditional scenarios: realistic conditions, fixed emissions, and fixed meteorology. The differences found between the model outputs were analyzed to quantify the relative contributions of emissions and meteorological factors. Emission-related gridded PM2.5 concentrations excluding the meteorological effects were predicted using multivariate regression models, whereas meteorological confounding effects on PM2.5 fluctuations were characterized by probabilistic functions. When the regression models and probabilistic functions were combined, fluctuations in the PM2.5 concentrations induced by emissions and meteorological factors were quantified for all model grid cells and regions. The method was then applied to assess the historical and future trends of PM2.5 concentrations and potential fluctuations on global, national, and city scales. The proposed method may thus be used to assess the effectiveness of mitigation actions.