Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: Magnitude, attribution, and uncertainty

Our understanding and quantification of global soil nitrous oxide (N₂ O) emissions and the underlying processes remain largely uncertain. Here, we assessed the effects of multiple anthropogenic and natural factors, including nitrogen fertilizer (N) application, atmospheric N deposition, manure N application, land cover change, climate change, and rising atmospheric CO₂ concentration, on global soil N₂ O emissions for the period 1861-2016 using a standard simulation protocol with seven process-based terrestrial biosphere models. Results suggest global soil N₂ O emissions have increased from 6.3 ± 1.1 Tg N₂ O-N/year in the preindustrial period (the 1860s) to 10.0 ± 2.0 Tg N₂ O-N/year in the recent decade (2007-2016). Cropland soil emissions increased from 0.3 Tg N₂ O-N/year to 3.3 Tg N₂ O-N/year over the same period, accounting for 82% of the total increase. Regionally, China, South Asia, and Southeast Asia underwent rapid increases in cropland N₂ O emissions since the 1970s. However, US cropland N₂ O emissions had been relatively flat in magnitude since the 1980s, and EU cropland N₂ O emissions appear to have decreased by 14%. Soil N₂ O emissions from predominantly natural ecosystems accounted for 67% of the global soil emissions in the recent decade but showed only a relatively small increase of 0.7 ± 0.5 Tg N₂ O-N/year (11%) since the 1860s. In the recent decade, N fertilizer application, N deposition, manure N application, and climate change contributed 54%, 26%, 15%, and 24%, respectively, to the total increase. Rising atmospheric CO₂ concentration reduced soil N₂ O emissions by 10% through the enhanced plant N uptake, while land cover change played a minor role. Our estimation here does not account for indirect emissions from soils and the directed emissions from excreta of grazing livestock. To address uncertainties in estimating regional and global soil N₂ O emissions, this study recommends several critical strategies for improving the process-based simulations.

Associations of wildfire smoke PM2.5 exposure with cardiorespiratory events in Colorado 2011-2014

BACKGROUND

Substantial increases in wildfire activity have been recorded in recent decades. Wildfires influence the chemical composition and concentration of particulate matter ≤2.5 μm in aerodynamic diameter (PM2.5). However, relatively few epidemiologic studies focus on the health impacts of wildfire smoke PM2.5 compared with the number of studies focusing on total PM2.5 exposure.

OBJECTIVES

We estimated the associations between cardiorespiratory acute events and exposure to smoke PM2.5 in Colorado using a novel exposure model to separate smoke PM2.5 from background ambient PM2.5 levels.

METHODS

We obtained emergency department visits and hospitalizations for acute cardiorespiratory outcomes from Colorado for May-August 2011-2014, geocoded to a 4 km geographic grid. Combining ground measurements, chemical transport models, and remote sensing data, we estimated smoke PM2.5 and non-smoke PM2.5 on a 1 km spatial grid and aggregated to match the resolution of the health data. Time-stratified, case-crossover models were fit using conditional logistic regression to estimate associations between fire smoke PM2.5 and non-smoke PM2.5 for overall and age-stratified outcomes using 2-day averaging windows for cardiovascular disease and 3-day windows for respiratory disease.

RESULTS

Per 1 μg/m3 increase in fire smoke PM2.5, statistically significant associations were observed for asthma (OR = 1.081 (1.058, 1.105)) and combined respiratory disease (OR = 1.021 (1.012, 1.031)). No significant relationships were evident for cardiovascular diseases and smoke PM2.5. Associations with non-smoke PM2.5 were null for all outcomes. Positive age-specific associations related to smoke PM2.5 were observed for asthma and combined respiratory disease in children, and for asthma, bronchitis, COPD, and combined respiratory disease in adults. No significant associations were found in older adults.

DISCUSSION

This is the first multi-year, high-resolution epidemiologic study to incorporate statistical and chemical transport modeling methods to estimate PM2.5 exposure due to wildfires. Our results allow for a more precise assessment of the population health impact of wildfire-related PM2.5 exposure in a changing climate.

Drivers for the poor air quality conditions in North China Plain during the COVID-19 outbreak

China's lockdown to control COVID-19 brought significant declines in air pollutant emissions, but haze was still a serious problem in North China Plain (NCP) during late-January to mid-February of 2020. We seek the potential causes for the poor air quality in NCP combining satellite data, ground measurements and model analyses. Efforts to constrain COVID-19 result in a drop-off of primary gaseous pollutants, e.g., -42.4% for surface nitrogen dioxide (NO2) and -38.9% for tropospheric NO2 column, but fine particulate matter (PM25) still remains high and ozone (O3) even increases sharply (+84.1%). Stagnant weather during COVID-19 outbreak, e.g., persistent low wind speed, frequent temperature inversion and wind convergence, is one of the major drivers for the poor air quality in NCP. The surface PM2.5 levels vary between -12.9~+15.1% in NCP driven by the varying climate conditions between the years 2000 and 2020. Besides, the persistent PM2.5 pollution might be maintained by the still intensive industrial and residential emissions (primary PM2.5), and increased atmospheric oxidants (+26.1% for ozone and +29.4% for hydroxyl radical) in response to the NO2 decline (secondary PM2.5). Further understanding the nonlinear response between atmospheric secondary aerosols and NOx emissions is meaningful to cope with the emerging air pollution problems in China.

Weakened growth of cropland-N2 O emissions in China associated with nationwide policy interventions

China has experienced rapid agricultural development over recent decades, accompanied by increased fertilizer consumption in croplands; yet, the trend and drivers of the associated nitrous oxide (N₂ O) emissions remain uncertain. The primary sources of this uncertainty are the coarse spatial variation of activity data and the incomplete model representation of N₂ O emissions in response to agricultural management. Here, we provide new data-driven estimates of cropland-N₂ O emissions across China in 1990-2014, compiled using a global cropland-N₂ O flux observation dataset, nationwide survey-based reconstruction of N-fertilization and irrigation, and an updated nonlinear model. In addition, we have evaluated the drivers behind changing cropland-N₂ O patterns using an index decomposition analysis approach. We find that China's annual cropland-N₂ O emissions increased on average by 11.2 Gg N/year² (p < .001) from 1990 to 2003, after which emissions plateaued until 2014 (2.8 Gg N/year² , p = .02), consistent with the output from an ensemble of process-based terrestrial biosphere models. The slowdown of the increase in cropland-N₂ O emissions after 2003 was pervasive across two thirds of China's sowing areas. This change was mainly driven by the nationwide reduction in N-fertilizer applied per area, partially due to the prevalence of nationwide technological adoptions. This reduction has almost offset the N₂ O emissions induced by policy-driven expansion of sowing areas, particularly in the Northeast Plain and the lower Yangtze River Basin. Our results underline the importance of high-resolution activity data and adoption of nonlinear model of N₂ O emission for capturing cropland-N₂ O emission changes. Improving the representation of policy interventions is also recommended for future projections.

Sensitivity of projected PM2.5- and O3-related health impacts to model inputs: A case study in mainland China

In China, fine particulate matter (PM_2.5) and ground-level ozone (O₃) are anticipated to continuously affect large populations in the coming decades. Simulations of the levels of these pollutants largely depend on emissions inputs, which are highly uncertain both in magnitude and spatial distribution. Our goal was to explore sensitivities of projected changes in PM_2.5- and O₃-related short-term health impacts in mainland China to emissions and other model inputs. We simulated winter PM_2.5 and summer O₃ concentrations using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) for both 2008 and 2050. We used three emission inventories in 2008 and four emissions scenarios in 2050. The resulting air pollutant concentrations were combined with eight population projections and three concentration-response functions (CRFs) to estimate future PM_2.5- and O₃-related health impacts including total, cardiovascular, and respiratory mortalities in mainland China. Multivariate analysis of variance was used to apportion the uncertainty due to different model parameters. Combinations of different parameters produced a wide range of national PM_2.5- and O₃-related mortalities. CRFs and present emissions each contribute 38%-56% and 20%-28% of the total sum of squares for PM_2.5-related mortalities. Future emissions are the largest source of uncertainty in O₃-related mortality estimates, contributing 24%-48% of total sum of squares. Our results suggest that conducting more epidemiological studies and constraining the present day emissions are essential for projecting future air pollutant-related health impacts in mainland China.

Household air pollution and personal exposure from burning firewood and yak dung in summer in the eastern Tibetan Plateau

This study assessed the sources, magnitudes, and chemical compositions of household air pollution (HAP) and personal exposure in traditional Tibetan households. We measured 24-h personal exposures to PM_2.5 and kitchen area black carbon (BC) concentrations, using MicroPEMs and microAeths, respectively. Particulate polycyclic aromatic hydrocarbon (PAH) and inorganic element concentrations were quantified via post analyses of a subset of MicroPEM sample filters. Household surveys regarding participant demographics, cookstove usage, household fuel, cooking behaviors, and lifestyles were collected. The results reaffirm that burning firewood and yak dung, mainly for cooking, leads to high PM_2.5 and BC exposures. The geometric mean concentration (95% confidence interval, CI) was 74.3 (53.6, 103) μg/m³ for PM_2.5 and the arithmetic mean ± standard deviation (SD) concentration was 4.90 ± 5.01 μg/m³ for BC and 292 ± 364 ng/m³ for 15 identified PAHs, respectively. The arithmetic mean ± SD of mass concentrations of 24 detected elements ranged from 0.76 ± 0.91 ng/m³ (Co) to 1.31 ± 1.35 μg/m³ (Si). Our statistical analyses further illustrated that the high concentrations of PM_2.5, BC, and most PAHs and metals, are significantly associated with nomadic village, poorer stove/chimney conditions and yak dung burning. The results from this study show that substantial HAP exposure is prevalent in Tibetan households and requires immediate actions to mitigate potential negative environmental health impacts. The observational data also revealed the possibility of other important sources (e.g. traffic and garbage burning) that have contributed to personal exposures. These findings improve our understanding of HAP exposure and potential health risks in Tibetan communities and will help inform strategies for reducing HAP in Tibetan households and beyond.

Critical Role of Simultaneous Reduction of Atmospheric Odd Oxygen for Winter Haze Mitigation

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 = O₃ + NO₂) 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.

Garbage Burning in South Asia: How Important Is It to Regional Air Quality?

Increasing air pollution in South Asia has serious consequences for air quality and human/ecosystem health within the region. South Asia, including India and Nepal, suffers from severe air pollution, including high concentrations of aerosols, as well as gaseous pollutants. One of the often-neglected sources contributing to the regional air pollution is garbage burning. It is mostly related to numerous yet small, open, uncontrolled fires burning diverse fuels, making it difficult to quantify activity and emissions. In this study, we attempted to quantify the total emissions due to garbage burning and its contribution to regional air quality, using new observational data, a new inventory, and a regional chemical transport model. We implemented the newly available emission factors (EFs) from a recent field campaign, Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE), which took place in April 2015. Using a chemical transport model-Weather Research and Forecasting model coupled with Chemistry version 3.5 (WRF-Chem)-and three emission scenarios, we assessed the impact of open garbage burning emissions on regional air quality. Our results show that garbage burning emissions could increase PM_2.5 concentrations by nearly 30% in India and Nepal, and result in ∼300 000 premature deaths from chronic obstructive pulmonary disease in the two countries.

Ship Emission Impacts on Air Quality and Human Health in the Pearl River Delta (PRD) Region, China, in 2015, With Projections to 2030

Ship emissions contribute to air pollution, increasing the adverse health impacts on people living in coastal cities. We estimated the impacts caused by ship emissions, both on air quality and human health, in 2015 and future (2030) within the Pearl River Delta (PRD) region of China. In addition, we assessed the potential health benefits of implementing an Emission Control Area (ECA) in the region by predicting avoided premature mortality with and without an ECA. In 2015, ship emissions increased PM2.5 concentrations and O3 mixing ratios by 1.4 μg/m3 and 1.9 ppb, respectively, within the PRD region. This resulted in 466 and 346 excess premature acute deaths from PM2.5 and O3, respectively. Premature mortality from chronic exposures was even more significant, with 2,085 and 852 premature deaths from ship-related PM2.5 and O3, respectively. In 2030, we projected the future ship emissions with and without an ECA, using two possible land scenarios. With an ECA, we predicted 76% reductions in SO2 and 13% reductions in NO x from the shipping sector. Assuming constant land emissions from 2015 in 2030 (2030 Constant scenario), we found that an ECA could avoid 811 PM2.5-related and 108 O3-related deaths from chronic exposures. Using 2030 Projected scenario for land emissions, we found that an ECA would avoid 1,194 PM2.5-related and 160 O3-related premature deaths in 2030. In both scenarios, implementing an ECA resulted in 30% fewer PM2.5-related premature deaths and 10% fewer O3-related premature deaths, illustrating the importance of reducing ship emissions.

Perspectives on Heavy Metal Soil Testing Among Community Gardeners in the United States: A Mixed Methods Approach

Community gardens offer numerous benefits, but there are also potential risks from exposure to chemical contaminants in the soil. Through the lens of the Theory of Planned Behavior, this mixed methods study examined community gardeners' beliefs and intentions to conduct heavy metal soil testing. The qualitative component involved five focus groups of community garden leaders in Atlanta, Georgia. Qualitative analysis of the focus group data revealed that heavy metal soil contamination was not frequently identified as a common gardening hazard and several barriers limited soil testing in community gardens. The focus group results informed the development of a questionnaire that was administered to 500 community gardeners across the United States. Logistic regression analysis revealed that the soil testing intention was associated with attitude (aOR = 2.46, 95% CI: 1.34, 4.53), subjective norms (aOR = 3.39 95% CI: 2.07, 5.57), and perceived behavioral control (aOR = 1.81, 95% CI: 1.10, 2.99). Study findings have implications for interventions involving community garden risk mitigation, particularly gardens that engage children and vulnerable populations.

Safe Community Gardening Practices: Focus Groups with Garden Leaders in Atlanta, Georgia

Although best management practices have been recommended by government agencies and non-profit organizations to reduce community gardeners' potential exposure to soil contaminants such as lead, some gardeners do not perform these practices. Understanding gardeners' beliefs and motivations is critical for effective promotion of safer gardening practices. This study, grounded in the Theory of Planned Behavior (TPB), employed five focus groups to investigate Atlanta community garden leaders' perspectives concerning three gardening practices: composting, hygiene behaviors, and mulching. These general practices are also considered safe gardening practices in that they can reduce exposure to toxicants in urban gardens. Qualitative analysis identified advantages and disadvantages; supporters and non-supporters; and barriers and facilitators that might influence gardeners' opinions regarding these behaviors. Gardeners expressed that more funding, volunteers, and training are needed to promote these behaviors. Gardeners noted that mulch and compost provided advantages such as improving soil quality, but a primary barrier was concern about contamination of source materials. Focus group participants did not directly associate composting and mulching with reduction of exposure to soil contaminants. Behavioral challenges related to hygiene included concerns about decreased exposure to salubrious bacteria, inadequate access to potable water, and limited availability of gloves and wipes. These study findings characterize factors that community garden stakeholders should consider when promoting safe gardening practices and interventions.

Household Air Pollution in a Changing Tibet: A Mixed Methods Ethnography and Indoor Air Quality Measurements

Household air pollution (HAP) is considered to be one of the largest environmental health risks in the world, being responsible each year for ~4.3 million deaths globally and 420,000 in China. Tibetan regions of China are known for pristine ambient air but several recent studies have concluded that the indoor air quality in Tibetan homes is compromised. Tibet is changing rapidly and this study sought to holistically understand HAP in relation to these changes. We took 28 measurements of fine particulate matter (PM_2.5) and black carbon (BC) concentrations in a variety of Tibetan dwellings in the Golog Tibetan Autonomous Prefecture. A semi-structured interview and ethnographic participant-observation were also administered with residents to better understand household behaviors and awareness of HAP. The highest concentrations of PM_2.5 and BC were found in the traditional yak hair tent, but nomads living in plastic tarp tents with improved stoves and stovepipes also had very compromised indoor air quality. All of the nomads in this study said they would prefer to use a fuel other than yak dung. More nomads expressed concern about their local glacier melting due to climate change than HAP, and indoor trash burning was seen at all sites. This study suggests that raising awareness of health and climate impacts due to HAP, in addition to having a better dialogue among the stakeholders and the residents in Tibet, is essential for obtaining better indoor air quality in the region.

The impact of cold weather on respiratory morbidity at Emory Healthcare in Atlanta

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.

Atlanta Residents' Knowledge Regarding Heavy Metal Exposures and Remediation in Urban Agriculture

Urban agriculture and gardening provide many health benefits, but the soil is sometimes at risk of heavy metal and metalloid (HMM) contamination. HMM, such as lead and arsenic, can result in adverse health effects for humans. Gardeners may face exposure to these contaminants because of their regular contact with soil and consumption of produce grown in urban areas. However, there is a lack of research regarding whether differential exposure to HMM may be attributed to differential knowledge of exposure sources. In 2018, industrial slag and hazardous levels of soil contamination were detected in West Atlanta. We conducted community-engaged research through surveys and follow-up interviews to understand awareness of slag, HMM in soil, and potential remediation options. Home gardeners were more likely to recognize HMM health effects and to cite health as a significant benefit of gardening than community gardeners. In terms of knowledge, participants were concerned about the potential health effects of contaminants in soil yet unconcerned with produce in their gardens. Gardeners’ knowledge on sources of HMM exposure and methods for remediation were low and varied based on racial group.

Plastic waste generation and emissions from the domestic open burning of plastic waste in Guatemala

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 PM2.5, and 2.4% of CO2 emissions in Guatemala may not be accounted for by excluding open plastic burning as a source.

Community-Engaged Assessment of Soil Lead Contamination in Atlanta Urban Growing Spaces

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.

Developing and Implementing In-Person and Virtual SoilSHOPs in Atlanta, Georgia, as a Community-Engaged Approach to Screen and Prevent Soil Lead Exposure

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.

Phytoremediation of Lead-Contaminated Soil in the Westside of Atlanta, GA

Phytoremediation has been explored as a cost-effective method to remediate soil Pb contamination. A greenhouse study was conducted to evaluate the efficacy of Vigna unguiculata, Brassica pekinensis, Gomphrena globose, and Helianthus annuus for removing and immobilizing Pb in soil collected from the Westside Lead Superfund site in Atlanta. Plants were cultivated in sampled soil with a Pb concentration of 515 ± 10 mg/kg for 60 days. Soils growing H. annuus were additionally treated with ethylenediaminetetraacetic acid (EDTA) (0.1 g/kg) or compost (20% soil blend) to assess their capabilities for enhancing phytoremediation. Mean post-phytoremediation Pb concentrations in the four plant species were 23.5, 25.7, 50.0, and 58.1 mg/kg dry weight (DW), respectively, and were substantially higher than 1.55 mg/kg DW in respective plant species grown in control soils with no Pb contamination. The highest Pb concentration, translocation factor, and biomass were found in V. unguiculate among four species without soil amendments. H. annuus treated with EDTA and compost resulted in a significant increase in the total Pb uptake and larger biomass compared to non-treated plants, respectively. Although this study found that V. unguiculata was the best candidate for Pb accumulation and immobilization among four species, soil remediation was limited to 54 mg/kg in a growing season. We find that it is critically important to perform phytostabilization in a secure manner, since Pb bioavailability of edible plant parts implies the potential risk associated with their unintentional consumption. Efficiently and effectively remediating Pb-contaminated soils in a low-cost manner needs to be further studied.

Submicron Aerosol Composition and Source Contribution across the Kathmandu Valley, Nepal, in Winter

The Kathmandu valley experiences an average wintertime PM1 concentration of ∼100 μg m-3 and daily peaks over 200 μg m-3. We present ambient nonrefractory PM1 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 PM1 (C-PM1) (49%) and black carbon (BC) was the second largest contributor (21%). The average background C-PM1 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 (SO4) 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-PM1, 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.

PRECIS-2 used as an implementation science tool for global environmental health: A cross-sectional evaluation of the Ecolectivos study protocol to reduce burning of household plastic waste in rural Guatemala

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.

Wintertime Air Quality across the Kathmandu Valley, Nepal: Concentration, Composition, and Sources of Fine and Coarse Particulate Matter

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 (PM2.5, PM10, and PM10-2.5) 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 PM2.5 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, PM10 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 PM2.5 and 34% of PM10. PM2.5 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 PM2.5 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.

Estimating personal exposures to household air pollution and plastic garbage burning among adolescent girls in Jalapa, Guatemala

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 (PM2.5), 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%). PM2.5 and BC were measured in n = 21 control and n = 20 intervention participants. Median concentrations of personal PM2.5 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).

The effect of farming techniques on degradation of DDT in historical cotton farms

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.