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The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign took place in and around the Kathmandu Valley and in the Indo-Gangetic Plain (IGP) of southern Nepal during April 2015. The source characterization phase targeted numerous important but undersampled (and often inefficient) combustion sources that are widespread in the developing world such as cooking with a variety of stoves and solid fuels, brick kilns, open burning of municipal solid waste (a.k.a. trash or garbage burning), crop residue burning, generators, irrigation pumps, and motorcycles. NAMaSTE produced the first, or rare, measurements of aerosol optical properties, aerosol mass, and detailed trace gas chemistry for the emissions from many of the sources. This paper reports the trace gas and aerosol measurements obtained by Fourier transform infrared (FTIR) spectroscopy, whole-air sampling (WAS), and photoacoustic extinctiometers (PAX; 405 and 870nm) based on field work with a moveable lab sampling authentic sources. The primary aerosol optical properties reported include emission factors (EFs) for scattering and absorption coefficients (EF Bscat, EF Babs, inm2kg-1 fuel burned), single scattering albedos (SSAs), and absorption Ångström exponents (AAEs). From these data we estimate black and brown carbon (BC, BrC) emission factors (gkg-1 fuel burned). The trace gas measurements provide EFs (gkg-1) for CO2, CO, CH4, selected non-methane hydrocarbons up to C10, a large suite of oxygenated organic compounds, NH3, HCN, NOx, SO2, HCl, HF, etc. (up to ∼ 80 gases in all). The emissions varied significantly by source, and light absorption by both BrC and BC was important for many sources. The AAE for dung-fuel cooking fires (4.63±0.68) was significantly higher than for wood-fuel cooking fires (3.01±0.10). Dung-fuel cooking fires also emitted high levels of NH3 (3.00±1.33gkg-1), organic acids (7.66±6.90gkg-1), and HCN (2.01±1.25gkg-1), where the latter could contribute to satellite observations of high levels of HCN in the lower stratosphere above the Asian monsoon. HCN was also emitted in significant quantities by several non-biomass burning sources. BTEX compounds (benzene, toluene, ethylbenzene, xylenes) were major emissions from both dung- (∼4.5gkg-1) and wood-fuel (∼1.5gkg-1) cooking fires, and a simple method to estimate indoor exposure to the many measured important air toxics is described. Biogas emerged as the cleanest cooking technology of approximately a dozen stove-fuel combinations measured. Crop residue burning produced relatively high emissions of oxygenated organic compounds (∼12gkg-1) and SO2 (2.54±1.09gkg-1). Two brick kilns co-firing different amounts of biomass with coal as the primary fuel produced contrasting results. A zigzag kiln burning mostly coal at high efficiency produced larger amounts of BC, HF, HCl, and NOx, with the halogenated emissions likely coming from the clay. The clamp kiln (with relatively more biomass fuel) produced much greater quantities of most individual organic gases, about twice as much BrC, and significantly more known and likely organic aerosol precursors. Both kilns were significant SO2 sources with their emission factors averaging 12.8±0.2gkg-1. Mixed-garbage burning produced significantly more BC (3.3±3.88gkg-1) and BTEX (∼4.5gkg-1) emissions than in previous measurements. For all fossil fuel sources, diesel burned more efficiently than gasoline but produced larger NOx and aerosol emission factors. Among the least efficient sources sampled were gasoline-fueled motorcycles during start-up and idling for which the CO EF was on the order of ∼700gkg-1 - or about 10 times that of a typical biomass fire. Minor motorcycle servicing led to minimal if any reduction in gaseous pollutants but reduced particulate emissions, as detailed in a companion paper (Jayarathne et al., 2016). A small gasoline-powered generator and an "insect repellent fire" were also among the sources with the highest emission factors for pollutants. These measurements begin to address the critical data gap for these important, undersampled sources, but due to their diversity and abundance, more work is needed.

We conducted simulations using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) version 3.5 to study air quality in East and South Asia at a spatial resolution of 20 km x 20 km. We find large discrepancies between two existing emissions inventories: the Regional Emission Inventory in Asia version 2 (REAS) and the Emissions Database for Global Atmospheric Research version 4.2 (EDGAR) at the provincial level in China, with maximum differences up to 500% for CO emissions, 190% for NO, and 160% for primary PM10. Such differences in the magnitude and the spatial distribution of emissions for various species lead to 40-70% difference in surface PM10 concentrations, 16-20% in surface O3 mixing ratios, and over 100% in SO2 and NO2 mixing ratios in the polluted areas of China. Our sensitivity run shows WRF-Chem is sensitive to emissions, with the REAS-based simulation reproducing observed concentrations and mixing ratios better than the EDGAR-based simulation for July 2007. We conduct further model simulations using REAS emissions for January, April, July, and October in 2007 and evaluate simulations with available ground-level observations. The model results show clear regional variations in the seasonal cycle of surface PM10 and O3 over East and South Asia. The model meets the air quality model performance criteria for both PM10 (mean fractional bias, MFB≤±60%) and O3 (MFB≤±15%) in most of the observation sites, although the model underestimates PM10 over Northeast China in January. The model predicts the observed SO2 well at sites in Japan, while it tends to overestimate SO2 in China in July and October. The model underestimates most observed NO2 in all four months. These findings suggest that future model development and evaluation of emission inventories and models are needed for particulate matter and gaseous pollutants in East and South Asia. [ABSTRACT FROM AUTHOR]

This study examines N2O emission estimates from five different atmospheric inversion frameworks based on chemistry transport models (CTMs). The five frameworks differ in the choice of CTM, meteorological data, prior uncertainties and inversion method but use the same prior emissions and observation data set. The posterior modelled atmospheric N2O mole fractions are compared to observations to assess the performance of the inversions and to help diagnose problems in the modelled transport. Additionally, the mean emissions for 2006 to 2008 are compared in terms of the spatial distribution and seasonality. Overall, there is a good agreement among the inversions for the mean global total emission, which ranges from 16.1 to 18.7 TgN yr-1 and is consistent with previous estimates. Ocean emissions represent between 31 and 38% of the global total compared to widely varying previous estimates of 24 to 38%. Emissions from the northern mid- to high latitudes are likely to be more important, with a consistent shift in emissions from the tropics and subtropics to the mid- to high latitudes in the Northern Hemisphere; the emission ratio for 0-30° N to 30-90° N ranges from 1.5 to 1.9 compared with 2.9 to 3.0 in previous estimates. The largest discrepancies across inversions are seen for the regions of South and East Asia and for tropical and South America owing to the poor observational constraint for these areas and to considerable differences in the modelled transport, especially inter-hemispheric exchange rates and tropical convective mixing. Estimates of the seasonal cycle in N2O emissions are also sensitive to errors in modelled stratosphere-to-troposphere transport in the tropics and southern extratropics. Overall, the results show a convergence in the global and regional emissions compared to previous independent studies. [ABSTRACT FROM AUTHOR]

We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected discrete air samples in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute of Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1-0.7% per year, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally gridded a priori N2O emissions over the 37 years since 1975. We then use the threedimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in recent years, most likely due to an increase in the use of nitrogenous fertilizers, as has been suggested by previous studies. [ABSTRACT FROM AUTHOR]

Background: Randomized controlled trials (RCTs) that evaluate the efficacy of an intervention remain underutilized in community-based environmental health research. RCTs that use a pragmatic design emphasize the effectiveness of interventions in complex, real world settings. Pragmatic trials may be especially relevant when community-based interventions address social and environmental determinants that threaten health equity. The revised Pragmatic Explanatory Continuum Indicator Summary (PRECIS-2) is a validated tool developed in 2015 by trialists to ensure that clinical trials are designed to fit their intended purpose, with an assessment of applicability of the trial results to specific contexts. The purpose of this cross-sectional study was to ask Ecolectivos study investigators and external implementation scientists to evaluate the Ecolectivos study protocol using the PRECIS-2 tool prior to the launch of the trial. Ecolectivos is an implementation science study, using a village-level cluster randomized controlled trial design, to assess a behavioral intervention to reduce household plastic waste burning in rural Guatemala., Methods: We invited 60 researchers to participate in an online survey between February 2022 and January 2023. Respondents were asked to review the Ecolectivos study protocol and provide scores for the nine PRECIS-2 domains (eligibility, recruitment, setting, organization, flexibility-delivery, flexibility-adherence, follow-up, primary outcome, and primary analysis), with short responses explaining their score. The PRECIS-2 tool is used to assess the degree of pragmatism, ranked on a five-point Likert scale from very explanatory (Checkley W, 2022) to very pragmatic (Ashcraft LE, 2024). Descriptive statistics were used to compare responses between Ecolectivos investigators and external evaluators., Results: Twenty-five respondents provided data. Among the nine domains, four were rated as pragmatic-eligibility, setting, flexibility-delivery, and primary analysis. Four were evaluated to be equally pragmatic as explanatory-recruitment, organization, flexibility-adherence, and primary outcome. One domain was primarily explanatory in nature-follow-up. Only one domain, eligibility, was statistically significantly different between Ecolectivos investigators and external evaluators, demonstrating that the two groups were broadly consistent in their opinions in eight of the nine study domains. Using the PRECIS-2 tool, we found that our study protocol was viewed as more pragmatic than explanatory, providing evidence to support the pragmatic approach of the Ecolectivos study goals, which is to reduce burning of plastic waste and plastic use in community settings using a behavioral intervention., Conclusions: By evaluating the degree of pragmatism within the nine domains, PRECIS-2 guides investigators to think about the applicability of potential results. Investigator assessment and communication regarding intervention protocols for community-level environmental interventions, their degree of pragmatism, and external validity are important for identifying strategies to address complex community problems. Our findings contribute to the growing body of literature that addresses greater research utility through pragmatic trial design, tying community environmental health interventions to the rigor of implementation science strategies., Competing Interests: The authors declare that they have no competing interests., (Copyright: © 2024 Thompson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Halocarbons are the primary driver behind ozone depletion and global warming. There is a vast observation gap in the Himalayan region. We report the field observations of thirty-four halocarbons at Nepal Climate Laboratory-Pyramid station and near the Mt. Qomolangma (Everest) base camp in the high Himalayas, including their atmospheric abundance and related changes over time. The dominant ozone depleting substances (ODSs) exhibited a declining trend, reflecting the effectiveness of the Montreal Protocol. However, a larger increase in HFCs and a higher abundance of unregulated chlorocarbons (e. g., CH 3 Cl) in this region compared to the global and North-Hemisphere values were found. It underscores that more attention is needed, not only for knowing where and how much HFCs and unregulated chlorocarbons are being emitted, but also for understanding its complicated role in climate change., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

DDT was used in the mid 20th century for crop and livestock production. After use, DDT and its degradates DDE and DDD (collectively DDX) remain in the environment for decades. A few studies have reported that the rate of degradation of DDT into its metabolites is affected by various farming techniques like tillage, irrigation, and use of fertilizers. However, most of these studies did not evaluate active farms, and none of them focused on the Southeast US or historical cotton farms. Therefore, in this study, we aimed to determine if different farming techniques affect the decomposition of DDT in Walton County, Georgia, where farms historically grew cotton. Five Walton County farms were sampled for soil, and churches were sampled as control sites. The extensive land history of the farms was recorded, and the soil levels of p,p'-DDT, p,p'-DDE, p,p'-DDD, o,p'-DDT, and o,p'-DDE were measured using gas chromatography-tandem mass spectrometry. All farm sites had detectable levels of p,p'-DDT, p,p'-DDE, and p,p'-DDD, while few sites had detectable levels of o,p'-DDT and o,p'-DDE. Tillage was found to speed up p,p'-DDE degradation, but there was no effect on p,p'-DDT degradation. Plowing was associated with an increase in decomposition of p,p'-DDT, but p,p'-DDE and p,p'-DDD were not significantly increased. The largest difference in the degradation of DDT was based on the fertilizer type. Natural fertilizer sped up degradation of p,p'-DDT and p,p'-DDE; synthetic fertilizer increased p,p'-DDE degradation, but not p,p'-DDT degradation., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Parinya Panuwet reports financial support was provided by National Institute of Environmental Health Sciences. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Waste collection services are uncommon in rural areas of low-resource countries, causing waste accumulation and subsequent dumping and burning of garbage. Air pollution from household garbage burning, including plastics, has been observed in Jalapa, Guatemala in addition to household air pollution (HAP) from cooking. Adolescent girls often help with these cooking and household tasks, but little is known about their exposures. We characterized 24-h exposures to HAP and household garbage burning in adolescent girls by measuring fine particulate matter (PM 2.5 ), black carbon (BC), urinary biomarkers of polycyclic aromatic hydrocarbons (PAHs), bisphenol A (BPA), and phthalates. We recruited 60 girls between 13 and 17 years of age who helped with cooking activities and lived with participants of the Household Air Pollution Intervention Network (HAPIN) trial. We recruited n = 30 girls each from the control (wood-burning stove) and intervention (liquefied petroleum gas stove) arms. We also measured real-time kitchen concentrations of BC in 20 homes (33%). PM 2.5 and BC were measured in n = 21 control and n = 20 intervention participants. Median concentrations of personal PM 2.5 and BC and kitchen BC were lower (p < 0.05) in the intervention arm by 87%, 80%, and 85%, respectively. PAH metabolite concentrations were lower (p < 0.001) for all nine metabolites in intervention (n = 26) compared to control participants (n = 29). Urinary BPA concentrations were 66% higher in participants who reported using cosmetics (p = 0.02), and phthalate concentrations were 63% higher in participants who had reported using hair products during the sample period (p = 0.05). Our results suggest that gas stoves can reduce HAP exposures among adolescents who are not primary cooks at home. Biomarkers of plastic exposure were not associated with intervention status, but some were elevated compared to age- and sex-matched participants of the National Health and Nutrition Examination Survey (NHANES)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Urban agriculture presents the opportunity for increased availability of local, fresh foods; however, exposure to lead soil contamination can occur through gardening in urban environments. Through a community-engaged partnership, we implemented Soil Screening, Health, Outreach and Partnerships (soilSHOPs), in-person and virtually, to screen soils for lead in Atlanta, Georgia. These soilSHOPs inform best practices for increasing awareness about lead exposure and grounding interventions in residents' lived experiences and also led the US Environmental Protection Agency to identify a Superfund site., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Urban agriculture is emerging as a method to improve food security and public health in cities across the United States. However, an increased risk of exposure to heavy metals and metalloids (HMM) exists through interaction with contaminated soil. Community-engaged research (CEnR) is one method that can promote the inclusion of all partners when studying exposures such as HMM in soil. Researchers and community gardeners co-designed this study to measure the concentrations of lead (Pb), using X-Ray Fluorescence (XRF) verified with Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in soils from 19 urban agricultural and residential sites in the Westside of Atlanta and three rural sites in Georgia. Seventeen other HMM were measured but not included in this study, because they did not pose risks to the community comparable to elevated Pb levels. Pb concentrations were compared to the Environmental Protection Agency (EPA)'s regional screening levels (RSLs) for residential soil and the University of Georgia (UGA) extension service's low-risk levels (LRLs) for agriculture. Soils from the majority of sites had levels below EPA RSLs for Pb, yet above the UGA LRL. However, soil Pb concentrations were three times higher than the EPA RSL on some sites that contained metal refining waste or slag. Our findings led to direct action by local and federal government agencies to initiate the cleanup of slag residue. Studies involving exposures to communities should engage those affected throughout the process for maximum impact., Competing Interests: The authors declare no conflicts of interest relevant to this study., (© 2023 The Authors. GeoHealth published by Wiley Periodicals LLC on behalf of American Geophysical Union.)

The Kathmandu Valley in Nepal experiences poor air quality, especially in the dry winter season. In this study, we investigated the concentration, chemical composition, and sources of fine and coarse particulate matter (PM 2.5 , PM 10 , and PM 10-2.5 ) at three sites within or near the Kathmandu Valley during the winter of 2018 as part of the second Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE 2). Daily PM 2.5 concentrations were very high throughout the study period, ranging 72-149 μg m -3 at the urban Ratnapark site in Kathmandu, 88-161 μg m -3 at the suburban Lalitpur site, and 40-74 μg m -3 at rural Dhulikhel on the eastern rim of the Kathmandu Valley. Meanwhile, PM 10 ranged 194-309, 174-377, and 64-131 μg m -3 , respectively. At the Ratnapark site, crustal materials from resuspended soil contributed an average of 11% of PM 2.5 and 34% of PM 10 . PM 2.5 was largely comprised of organic carbon (OC, 28-30% by mass) and elemental carbon (EC, 10-14% by mass). As determined by chemical mass balance source apportionment modeling, major PM 2.5 OC sources were garbage burning (15-21%), biomass burning (10-17%), and fossil fuel (14-26%). Secondary organic aerosol (SOA) contributions from aromatic volatile organic compounds (13-23% OC) were larger than those from isoprene (0.3-0.5%), monoterpenes (0.9-1.4%), and sesquiterpenes (3.6-4.4%). Nitro-monoaromatic compounds-of interest due to their light-absorbing properties and toxicity-indicate the presence of biomass burning-derived SOA. Knowledge of primary and secondary PM sources can facilitate air quality management in this region., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The Kathmandu valley experiences an average wintertime PM 1 concentration of ∼100 μg m -3 and daily peaks over 200 μg m -3 . We present ambient nonrefractory PM 1 chemical composition, and concentration measured by a mini aerosol mass spectrometer (mAMS) sequentially at Dhulikhel (on the valley exterior), then urban Ratnapark, and finally suburban Lalitpur in winter 2018. At all sites, organic aerosol (OA) was the largest contributor to combined PM 1 (C-PM 1 ) (49%) and black carbon (BC) was the second largest contributor (21%). The average background C-PM 1 at Dhulikhel was 48 μg m -3 ; the urban enhancement was 120% (58 μg m -3 ). BC had an average of 6.1 μg m -3 at Dhulikhel, an urban enhancement of 17.4 μg m -3 . Sulfate (SO 4 ) was 3.6 μg m -3 at Dhulikhel, then 7.5 μg m -3 at Ratnapark, and 12.0 μg m -3 at Lalitpur in the brick kiln region. Chloride (Chl) increased by 330 and 250% from Dhulikhel to Ratnapark and Lalitpur on average. Positive matrix factorization (PMF) identified seven OA sources, four primary OA sources, hydrocarbon-like (HOA), biomass burning (BBOA), trash burning (TBOA), a sulfate-containing local OA source (sLOA), and three secondary oxygenated organic aerosols (OOA). OOA was the largest fraction of OA, over 50% outside the valley and 36% within. HOA (traffic) was the most prominent primary source, contributing 21% of all OA and 44% of BC. Brick kilns were the second largest contributor to C-PM 1 , 12% of OA, 33% of BC, and a primary emitter of aerosol sulfate. These results, though successive, indicate the importance of multisite measurements to understand ambient particulate matter concentration heterogeneity across urban regions., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Domestic, or household-level, open burning of plastic waste is a source of air pollutants and greenhouse gases that are often neglected in emission inventories. Domestic open burning is a considerable concern in Guatemala due to the lack of access to waste collection services, particularly in rural areas. This paper offers the first attempt to estimate emissions from the domestic open burning of waste at the city and departmental levels in Guatemala. Data were collected from the Xalapán region of Jalapa, Guatemala and analyzed to determine the change in plastic waste generation over time as well as the socioeconomic factors that may affect the extent of plastic waste generation and burning. The annual per capita masses of plastic waste burned were used to estimate emissions from domestic open burning of plastic waste in the region of Xalapán, the cities of Jutiapa and Guatemala city, and all 22 departments in Guatemala. Our results show that rural areas burn more waste domestically, likely because of a lack of access to waste collection, and 30.4% of OC, 24.0% of BC, 23.6% of PM 2.5 , and 2.4% of CO 2 emissions in Guatemala may not be accounted for by excluding open plastic burning as a source., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Background: Research on temperature and respiratory hospitalizations is lacking in the southeastern U.S. where cold weather is relatively rare. This retrospective study examined the association between cold waves and pneumonia and influenza (P&I) emergency department (ED) visits and hospitalizations in three metro-Atlanta hospitals., Methods: We used a case-crossover design, restricting data to the cooler seasons of 2009-2019, to determine whether cold waves influenced ED visits and hospitalizations. This analysis considered effects by race/ethnicity, age, sex, and severity of comorbidities. We used generalized additive models and distributed lag non-linear models to examine these relationships over a 21-day lag period., Results: The odds of a P&I ED visit approximately one week after a cold wave were increased by as much as 11%, and odds of an ED visit resulting in hospitalization increased by 8%. For ED visits on days with minimum temperatures >20 °C, there was an increase of 10-15% in relative risk (RR) for short lags (0-2 days), and a slight decrease in RR (0-5%) one week later. For minimum temperatures <0 °C, RR decreased at short lags (5-10%) before increasing (1-5%) one week later. Hospital admissions exhibited a similar, but muted, pattern., Conclusion: Unusually cold weather influenced P&I ED visits and admissions in this population., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The lockdown due to COVID-19 created a rare opportunity to examine the nonlinear responses of secondary aerosols, which are formed through atmospheric oxidation of gaseous precursors, to intensive precursor emission reductions. Based on unique observational data sets from six supersites in eastern China during 2019-2021, we found that the lockdown caused considerable decreases (32-61%) in different secondary aerosol components in the study region because of similar-degree precursor reductions. However, due to insufficient combustion-related volatile organic compound (VOC) reduction, odd oxygen (O x = O 3 + NO 2 ) concentration, an indicator of the extent of photochemical processing, showed little change and did not promote more decreases in secondary aerosols. We also found that the Chinese provinces and international cities that experienced reduced O x during the lockdown usually gained a greater simultaneous PM 2.5 decrease than other provinces and cities with an increased O x . Therefore, we argue that strict VOC control in winter, which has been largely ignored so far, is critical in future policies to mitigate winter haze more efficiently by reducing O x simultaneously.