publications

2024

1. North American Fine Particulate Matter Chemical Composition for 2000–2022 from Satellites, Models, and Monitors: The Changing Contribution of Wildfires

   Aaron Donkelaar, Randall V. Martin, Bonne Ford, and 4 more authors

   ACS ES&T Air, 2024

   Publisher: American Chemical Society

   Abs Article

   Air quality management benefits from an in-depth understanding of the emissions associated with, and composition of, local PM2.5 concentrations. Here, we investigate the changing role of biomass burning emissions to North American PM2.5 exposure by combining multiple satellite-, ground-, and simulation-based data sets biweekly at a 0.01° × 0.01° resolution from 2000 to 2022. We also developed a Buffered Leave Cluster Out (BLeCO) method to address autocorrelation and computational cost in cross-validation. Biomass burning emissions contribute an increasingly large fraction to PM2.5 exposure in the United States and Canada, with national annual population-weighted mean contributions increasing from 0.4 μg/m3 (3–5%) in 2000–2004 to 0.8–0.9 μg/m3 (9–14%) by 2019–2022, led by western North American 2019–2022 annual contributions of 1.4–1.9 μg/m3 (15–27%) and maximum seasonal contributions of 3.3–5.5 μg/m3 (29–49%). Other components such as nonbiomass burning Organic Matter (OM) and nitrate can be regionally as (or more) important, albeit with distinct seasonal variability. The contribution of total OM to PM2.5 exposure in the United States in 2016–2022 is 42.2%, comparable to all other anthropogenically sourced components combined. Comparison of BLeCO and random 10-fold cross-validation suggests that random 10-fold cross-validation may significantly underrepresent true uncertainty for total PM2.5 concentrations due to the clustered nature of PM2.5 ground-based monitoring.

2. Toward Fine Horizontal Resolution Global Simulations of Aerosol Sectional Microphysics: Advances Enabled by GCHP-TOMAS

   Betty Croft, Randall V. Martin, Rachel Y.-W. Chang, and 15 more authors

   Journal of Advances in Modeling Earth Systems, 2024

   Abs Article

   Global modeling of aerosol-particle number and size is important for understanding aerosol effects on Earth’s climate and air quality. Fine-resolution global models are desirable for representing nonlinear aerosol-microphysical processes, their nonlinear interactions with dynamics and chemistry, and spatial heterogeneity. However, aerosol-microphysical simulations are computationally demanding, which can limit the achievable global horizontal resolution. Here, we present the first coupling of the TwO-Moment Aerosol Sectional (TOMAS) microphysics scheme with the High-Performance configuration of the GEOS-Chem model of atmospheric composition (GCHP), a coupling termed GCHP-TOMAS. GCHP’s architecture allows massively parallel GCHP-TOMAS simulations including on the cloud, using hundreds of computing cores, faster runtimes, more memory, and finer global horizontal resolution (e.g., 25 km × 25 km, 7.8 × 105 model columns) versus the previous single-node capability of GEOS-Chem-TOMAS (tens of cores, 200 km × 250 km, 1.3 × 104 model columns). GCHP-TOMAS runtimes have near-ideal scalability with computing-core number. Simulated global-mean number concentrations increase (dominated by free-tropospheric over-ocean sub-10-nm-diameter particles) toward finer GCHP-TOMAS horizontal resolution. Increasing the horizontal resolution from 200 km × 200–50 km × 50 km increases the global monthly mean free-tropospheric total particle number by 18.5%, and over-ocean sub-10-nm-diameter particles by 39.8% at 4-km altitude. With a cascade of contributing factors, free-tropospheric particle-precursor concentrations increase (32.6% at 4-km altitude) with resolution, promoting new-particle formation and growth that outweigh coagulation changes. These nonlinear effects have the potential to revise current understanding of processes controlling global aerosol number and aerosol impacts on Earth’s climate and air quality.

3. Impact of the 2022 New Mexico, US wildfires on air quality and health

   Kamal J. Maji, Bonne Ford, Zongrun Li, and 14 more authors

   Science of The Total Environment, 2024

   Abs Article

   The 2022 wildfires in New Mexico, United States, were unparalleled compared to past wildfires in the state in both their scale and intensity, resulting in poor air quality and a catastrophic loss of habitat and livelihood. Among all wildfires in New Mexico in 2022, six wildfires were selected for our study based on the size of the burn area and their proximity to populated areas. These fires accounted for approximately 90 % of the total burn area in New Mexico in 2022. We used a regional chemical transport model and data-fusion technique to quantify the contribution of these six wildfires (April 6 to August 22) on particulate matter (PM2.5: diameter ≤ 2.5 μm) and ozone (O3) concentrations, as well as the associated health impacts from short-term exposure. We estimated that these six wildfires emitted 152 thousand tons of PM2.5 and 287 thousand tons of volatile organic compounds to the atmosphere. We estimated that the average daily wildfire smoke PM2.5 across New Mexico was 0.3 μg/m3, though 1 h maximum exceeded 120 μg/m3 near Santa Fe. Average wildfire smoke maximum daily average 8-h O3 (MDA8-O3) contribution was 0.2 ppb during the study period over New Mexico. However, over the state 1 h maximum smoke O3 exceeded 60 ppb in some locations near Santa Fe. Estimated all-cause excess mortality attributable to short term exposure to wildfire PM2.5 and MDA8-O3 from these six wildfires were 18 (95 % Confidence Interval (CI), 15–21) and 4 (95 % CI: 3–6) deaths. Additionally, we estimate that wildfire PM2.5 was responsible for 171 (95 %: 124–217) excess cases of asthma emergency department visits. Our findings underscore the impact of wildfires on air quality and human health risks, which are anticipated to intensify with global warming, even as local anthropogenic emissions decline.

4. Quantifying Prescribed‐Fire Smoke Exposure Using Low‐Cost Sensors and Satellites: Springtime Burning in Eastern Kansas

   Olivia Sablan, Bonne Ford, Emily Gargulinski, and 12 more authors

   GeoHealth, 2024

   Article

2023

1. Air Pollution, weather, and agricultural worker productivity

   Alexandra E. Hill, Jesse Burkhardt, Jude Bayham, and 4 more authors

   American Journal of Agricultural Economics, 2023

   Abs Article

   Outdoor agricultural workers often work in harsh environmental conditions, including high temperatures and poor air quality. This paper studies how these factors impact worker productivity, which can have implications for worker health, well-being, and income as well as farm payroll, production, and profitability. Our analysis uses 6 years of payroll records of harvesters on two large farms combined with pollution and weather monitor data from multiple sources. We address simultaneity issues by exploring pollution measurements from nearby upwind and downwind monitors and incorporating an alternative PM2.5 measure that better captures ambient or regional concentration. Across all specifications, results suggest that heightened concentrations of ground-level ozone and PM2.5 are associated with reduced productivity. In our main specification, we find that one standard deviation increases in ozone and PM2.5 are associated with reductions in productivity of 2% and 1.1%, respectively.

2. A national crowdsourced network of low-cost fine particulate matter and aerosol optical depth monitors: results from the 2021 wildfire season in the United States

   Eric A. Wendt, Bonne Ford, Michael Cheeseman, and 10 more authors

   Environmental Science: Atmospheres, 2023

   Abs Article

   Fine particulate matter (PM2.5) is a leading contributor to premature death, disease, and environmental degradation globally. Wildfire smoke is a primary source of air pollution in the United States. However, reference-grade ground monitors are cost prohibitive to deploy at the spatial scales needed to assess the variability of wildfire smoke. In many regions lacking adequate monitoring, health impact assessments and epidemiological studies on smoke may rely on satellite-based instruments, which estimate PM2.5 based on Aerosol Optical Depth (AOD). However, AOD measurements may not capture surface-level impacts; thus, measurements in under-monitored regions are necessary to interpret satellite observations. While low-cost PM2.5 sensors have been deployed at large scales, these sensors typically lack AOD measurement capability. In prior work, we designed the Aerosol Mass and Optical Depth (AMODv2) sampler, which can simultaneously measure PM2.5 (optical and gravimetric filter-based) and AOD. In this work, we distributed AMODv2s to volunteers at 31 locations in the contiguous United States, forming a nationwide network for the summer of 2021. A majority of our network was successful, with 86.6% of sampling periods resulting in a valid sample. We found our AOD sensors agreed closely with nearby (<25 km) reference monitor measurements (taken <180 seconds apart), with mean absolute error results of 0.03, 0.02, 0.02, and 0.03 at 440, 500, 675, and 870 nm, respectively. In a regional analysis of wildfire smoke, we observed elevated PM2.5 and AOD on smoky days at study sites in most regions, which led to similar PM2.5 : AOD ratios regardless of smoke. However, at the California study sites, median PM2.5 remained similar on smoky days relative to non-smoky days, while AOD increased, implying that the smoke may have been lofted above the surface during the study period. At the California study sites, the median PM2.5 : AOD ratio was 67.2 μg m−3 on non-smoky days, compared with 30.2 μg m−3 on smoky days. At study sites in other regions, the average ratio was 24.7 to 33.5 μg m−3 on non-smoky days and 20.3 to 29.4 μg m−3 on smoky days. We show that paired PM2.5 and AOD measurements collected by a crowdsourced network can highlight anomalies in air quality during smoke events and provide insights into the relationship between satellite-based and ground-based air quality observations.

3. A Culture of Fire: Identifying Community Risk Perceptions Surrounding Prescribed Burning in the Flint Hills, Kansas

   Zoey Rosen, Giovanna Henery, Kellin Slater, and 5 more authors

   Journal of Applied Communications, Jan 2023

   Abs Article

   In the Flint Hills region of eastern Kansas, there is a long tradition of spring prescribed burns. However, air quality concerns in downwind communities have sparked conversation regarding the environmental and social impacts of these burns. This study aimed to identify the risk perceptions associated with prescribed burns using two theoretical frameworks: the social amplification of risk framework and the protective action decision model. In April 2022, we conducted 18 in-depth, semi-structured interviews with Flint Hills community members from different social stations. Participants identified several benefits of prescribed burns: cattle production gains, invasive species management, prairie ecological health maintenance, and wildfire prevention. Some participants viewed prescribed burning as a protective response. However, risk perceptions differed between rural and urban participants: rural community members were primarily concerned with prescribed fires that went out of control, while those in downwind cities were primarily concerned with smoke exposure. Participants sometimes used protective actions to mitigate their risks, but also explained the complexities of changing burn practices that are integral to the local culture, economies, and greater society. Additionally, formal communication of health and safety risks from prescribed burns is not uniform across Kansas counties. We therefore recommend systematic county and statewide communication of burn practices and protective behaviors. Understanding community perceptions of the risks and effects of prescribed burns, and any protective actions taken, can inform how professional communicators approach burning in similar agricultural and ranching communities.

2022

1. Disparities in Air Pollutants Across Racial, Ethnic, and Poverty Groups at US Public Schools

   Michael J. Cheeseman, Bonne Ford, Susan C. Anenberg, and 8 more authors

   GeoHealth, Jan 2022

   Abs Article

   We investigate socioeconomic disparities in air quality at public schools in the contiguous US using high resolution estimates of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) concentrations. We find that schools with higher proportions of people of color (POC) and students eligible for the federal free or reduced lunch program, a proxy for poverty level, are associated with higher pollutant concentrations. For example, we find that the median annual NO2 concentration for White students, nationally, was 7.7 ppbv, compared to 9.2 ppbv for Black and African American students. Statewide and regional disparities in pollutant concentrations across racial, ethnic, and poverty groups are consistent with nationwide results, where elevated NO2 concentrations were associated with schools with higher proportions of POC and higher levels of poverty. Similar, though smaller, differences were found in PM2.5 across racial and ethnic groups in most states. Racial, ethnic, and economic segregation across the rural-urban divide is likely an important factor in pollution disparities at US public schools. We identify distinct regional patterns of disparities, highlighting differences between California, New York, and Florida. Finally, we highlight that disparities exist not only across urban and non-urban lines but also within urban environments.

2. Outside in: the relationship between indoor and outdoor particulate air quality during wildfire smoke events in western US cities

   Katelyn O’Dell, Bonne Ford, Jesse Burkhardt, and 5 more authors

   Environmental Research: Health, Nov 2022

   Abs Article

   Previous research on the health and air quality impacts of wildfire smoke has largely focused on the impact of smoke on outdoor air quality; however, many people spend a majority of their time indoors. The quality of indoor air on smoke-impacted days is largely unknown. In this analysis, we use publicly available data from an existing large network of low-cost indoor and outdoor fine particulate matter (PM2.5) monitors to quantify the relationship between indoor and outdoor particulate air quality on smoke-impacted days in 2020 across the western United States (US). We also investigate possible regional and socioeconomic trends in this relationship for regions surrounding six major cities in the western US. We find indoor PM2.5 concentrations are 82% or 4.2 µg m−3 (median across all western US indoor monitors for the year 2020; interquartile range, IQR: 2.0–7.2 µg m−3) higher on smoke-impacted days compared to smoke-free days. Indoor/outdoor PM2.5 ratios show variability by region, particularly on smoke-free days. However, we find the ratio of indoor/outdoor PM2.5 is less than 1 (i.e. indoor concentrations lower than outdoor) at nearly all indoor-outdoor monitor pairs on smoke-impacted days. Although typically lower than outdoor concentrations on smoke-impacted days, we find that on heavily smoke-impacted days (outdoor PM2.5 \textgreater 55 µg m−3), indoor PM2.5 concentrations can exceed the 35 µg m−3 24 h outdoor standard set by the US Environmental Protection Agency. Further, total daily-mean indoor PM2.5 concentrations increase by 2.1 µg m−3 with every 10 µg m−3 increase in daily-mean outdoor PM2.5. (median of statistically significant linear regression slopes across all western US monitor pairs; IQR: 1.0–4.3 µg m−3) on smoke-impacted days. These results show that for indoor environments in the western US included in our analysis, remaining indoors during smoke events is currently an effective, but limited, strategy to reduce PM2.5 exposure.

2021

1. Differential Cardiopulmonary Health Impacts of Local and Long-Range Transport of Wildfire Smoke

   Sheryl Magzamen, Ryan W. Gan, Jingyang Liu, and 7 more authors

   GeoHealth, Nov 2021

   Abs Article

   We estimated cardiopulmonary morbidity and mortality associated with wildfire smoke (WFS) fine particulate matter (PM2.5) in the Front Range of Colorado from 2010 to 2015. To estimate WFS PM2.5, we developed a daily kriged PM2.5 surface at a 15 × 15 km resolution based on the Environmental Protection Agency Air Quality System monitors for the western United States; we subtracted out local seasonal-average PM2.5 of nonsmoky days, identified using satellite-based smoke plume estimates, from the local daily estimated PM2.5 if smoke was identified by National Oceanic and Atmospheric Administration’s Hazard Mapping System. We implemented time-stratified case-crossover analyses to estimate the effect of a 10 µg/m3 increase in WFS PM2.5 with cardiopulmonary hospitalizations and deaths using single and distributed lag models for lags 0–5 and distinct annual impacts based on local and long-range smoke during 2012, and long-range transport of smoke in 2015. A 10 µg/m3 increase in WFS was associated with all respiratory, asthma, and chronic obstructive pulmonary disease hospitalizations for lag day 3 and hospitalizations for ischemic heart disease at lag days 2 and 3. Cardiac arrest deaths were associated with WFS PM2.5 at lag day 0. For 2012 local wildfires, asthma hospitalizations had an inverse association with WFS PM2.5 (OR: 0.716, 95% CI: 0.517–0.993), but a positive association with WFS PM2.5 during the 2015 long-range transport event (OR: 1.455, 95% CI: 1.093–1.939). Cardiovascular mortality was associated with the 2012 long-range transport event (OR: 1.478, 95% CI: 1.124–1.944).

2. Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem

   Katelyn O’Dell, Kelsey Bilsback, Bonne Ford, and 4 more authors

   GeoHealth, Nov 2021

   Abs Article

   As anthropogenic emissions continue to decline and emissions from landscape (wild, prescribed, and agricultural) fires increase across the coming century, the relative importance of landscape-fire smoke on air quality and health in the United States (US) will increase. Landscape fires are a large source of fine particulate matter (PM2.5), which has known negative impacts on human health. The seasonal and spatial distribution, particle composition, and co-emitted species in landscape-fire emissions are different from anthropogenic sources of PM2.5. The implications of landscape-fire emissions on the sub-national temporal and spatial distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. We use a health impact assessment with observation-based smoke PM2.5 to determine the sub-national distribution of mortality and the sub-national and sub-annual distribution of asthma morbidity attributable to US smoke PM2.5 from 2006 to 2018. We estimate disability-adjusted life years (DALYs) for PM2.5 and 18 gas-phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of mortality (74%) and asthma morbidity (on average 75% across 2006–2018) attributable to smoke PM2.5 occurs outside the West, due to higher population density in the East. Across the US, smoke-attributable asthma morbidity predominantly occurs in spring and summer. The number of DALYs associated with smoke PM2.5 is approximately three orders of magnitude higher than DALYs associated with gas-phase smoke HAPs. Our results indicate awareness and mitigation of landscape-fire smoke exposure is important across the US.

3. Associations Between Wildfire‐Related PM2.5 and Intensive Care Unit Admissions in the United States, 2006–2015

   Cecilia Sorensen, John A. House, Katelyn O’Dell, and 6 more authors

   GeoHealth, May 2021

   Abs Article

   Wildfire smoke is a growing public health concern in the United States. Numerous studies have documented associations between ambient smoke exposure and severe patient outcomes for single‐fire seasons or limited geographic regions. However, there are few national‐scale health studies of wildfire smoke in the United States, few studies investigating Intensive Care Unit (ICU) admissions as an outcome, and few specifically framed around hospital operations. This study retrospectively examined the associations between ambient wildfire‐related PM2.5 at a hospital ZIP code with total hospital ICU admissions using a national‐scale hospitalization data set. Wildfire smoke was characterized using a combination of kriged PM2.5 monitor observations and satellite‐derived plume polygons from National Oceanic and Atmospheric Administration’s Hazard Mapping System. ICU admissions data were acquired from Premier, Inc. and encompass 15%–20% of all U.S. ICU admissions during the study period. Associations were estimated using a distributed‐lag conditional Poisson model under a time‐stratified case‐crossover design. We found that a 10 μg/m3 increase in daily wildfire PM2.5 was associated with a 2.7% (95% CI: 1.3, 4.1; p = 0.00018) increase in ICU admissions 5 days later. Under stratification, positive associations were found among patients aged 0–20 and 60+, patients living in the Midwest Census Region, patients admitted in the years 2013–2015, and non‐Black patients, though other results were mixed. Following a simulated severe 7‐day 120 μg/m3 smoke event, our results predict ICU bed utilization peaking at 131% (95% CI: 43, 239; p \textless 10−5) over baseline. Our work suggests that hospitals may need to preposition vital critical care resources when severe smoke events are forecast., Associations between smoke PM2.5 and ICU admissions were estimated using a national‐scale cohortSmoke PM2.5 was associated with modest changes in ICU admissionsA simulated smoke wave was found to impose severe strain on ICU resources

4. Evolution of Acyl Peroxynitrates (PANs) in Wildfire Smoke Plumes Detected by the Cross-Track Infrared Sounder (CrIS) Over the Western U.S. During Summer 2018

   Julieta F. Juncosa Calahorrano, Vivienne H. Payne, Susan Kulawik, and 4 more authors

   Geophysical Research Letters, May 2021

   Abs Article

   We use observations of acyl peroxynitrates (PANs) from the Cross-Track Infrared Sounder (CrIS) to investigate PANs over the western U.S. during the summer 2018 wildfire season. This period coincides with the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN). When combined with favorable background conditions, the resolution and sensitivity of CrIS is sufficient to observe the production of PANs in smoke plumes. CrIS PANs normalized excess mixing ratios with respect to CO (NEMRs) in the Pole Creek Fire increase from 0.2% to 0.4% within 3–4 hr of physical aging, consistent with in situ NEMRs. CrIS is also able to detect PANs enhancements in plumes that have been transported hours to days downwind. On average for summer 2018, 19–56% of PANs in the free troposphere during the afternoon over the western U.S. can be attributed to smoke.

5. A low-cost monitor for simultaneous measurement of fine particulate matter and aerosol optical depth – Part 3: Automation and design improvements

   Eric A. Wendt, Casey Quinn, Christian L’Orange, and 10 more authors

   Atmospheric Measurement Techniques, Sep 2021

   Abs Article

   Atmospheric particulate matter smaller than 2.5 µm in diameter (PM2.5) has a negative impact on public health, the environment, and Earth’s climate. Consequently, a need exists for accurate, distributed measurements of surface-level PM2.5 concentrations at a global scale. Existing PM2.5 measurement infrastructure provides broad PM2.5 sampling coverage but does not adequately characterize community-level air pollution at high temporal resolution. This motivates the development of low-cost sensors which can be more practically deployed in spatial and temporal configurations currently lacking proper characterization. Wendt et al. (2019) described the development and validation of a first-generation device for low-cost measurement of AOD and PM2.5: the Aerosol Mass and Optical Depth (AMODv1) sampler. Ford et al. (2019) describe a citizen-science field deployment of the AMODv1 device. In this paper, we present an updated version of the AMOD, known as AMODv2, featuring design improvements and extended validation to address the limitations of the AMODv1 work. The AMODv2 measures AOD and PM2.5 at 20 min time intervals. The sampler includes a motorized Sun tracking system alongside a set of four optically filtered photodiodes for semicontinuous, multiwavelength (current version at 440, 500, 675, and 870 nm) AOD sampling. Also included are a Plantower PMS5003 sensor for time-resolved optical PM2.5 measurements and a pump/cyclone system for time-integrated gravimetric filter measurements of particle mass and composition. AMODv2 samples are configured using a smartphone application, and sample data are made available via data streaming to a companion website (https://csu-ceams.com/, last access: 16 July 2021). We present the results of a 9 d AOD validation campaign where AMODv2 units were co-located with an AERONET (Aerosol Robotics Network) instrument as the reference method at AOD levels ranging from 0.02 ± 0.01 to 1.59 ± 0.01. We observed close agreement between AMODv2s and the reference instrument with mean absolute errors of 0.04, 0.06, 0.03, and 0.03 AOD units at 440, 500, 675, and 870 nm, respectively. We derived empirical relationships relating the reference AOD level to AMODv2 instrument error and found that the mean absolute error in the AMODv2 deviated by less than 0.01 AOD units between clear days and elevated-AOD days and across all wavelengths. We identified bias from individual units, particularly due to calibration drift, as the primary source of error between AMODv2s and reference units. In a test of 15-month calibration stability performed on 16 AMOD units, we observed median changes to calibration constant values of −7.14 %, −9.64 %, −0.75 %, and −2.80 % at 440, 500, 675, and 870 nm, respectively. We propose annual recalibration to mitigate potential errors from calibration drift. We conducted a trial deployment to assess the reliability and mechanical robustness of AMODv2 units. We found that 75 % of attempted samples were successfully completed in rooftop laboratory testing. We identify several failure modes in the laboratory testing and describe design changes that we have since implemented to reduce failures. We demonstrate that the AMODv2 is an accurate, stable, and low-cost platform for air pollution measurement. We describe how the AMODv2 can be implemented in spatial citizen-science networks where reference-grade sensors are economically impractical and low-cost sensors lack accuracy and stability.

2020

1. Hazardous Air Pollutants in Fresh and Aged Western US Wildfire Smoke and Implications for Long-Term Exposure

   Katelyn O’Dell, Rebecca S. Hornbrook, Wade Permar, and 12 more authors

   Environmental Science & Technology, Oct 2020

   Abs Article

   Wildfires have a significant adverse impact on air quality in the United States (US). To understand the potential health impacts of wildfire smoke, many epidemiology studies rely on concentrations of fine particulate matter (PM) as a smoke tracer. However, there are many gas-phase hazardous air pollutants (HAPs) identified by the Environmental Protection Agency (EPA) that are also present in wildfire smoke plumes. Using observations from the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN), a 2018 aircraft-based field campaign that measured HAPs and PM in western US wildfire smoke plumes, we identify the relationships between HAPs and associated health risks, PM, and smoke age. We find the ratios between acute, chronic noncancer, and chronic cancer HAPs health risk and PM in smoke decrease as a function of smoke age by up to 72% from fresh (\textless1 day of aging) to old (\textgreater3 days of aging) smoke. We show that acrolein, formaldehyde, benzene, and hydrogen cyanide are the dominant contributors to gas-phase HAPs risk in smoke plumes. Finally, we use ratios of HAPs to PM along with annual average smoke-specific PM to estimate current and potential future smoke HAPs risks.

2. A Decadal Climatology of Chemical, Physical, and Optical Properties of Ambient Smoke in the Western and Southeastern United States

   Qijing Bian, Bonne Ford, Jeffrey R. Pierce, and 1 more author

   Journal of Geophysical Research: Atmospheres, Oct 2020

   Abs Article

   Biomass burning is a major source of summertime fine particulate matter in the United States, degrading air quality and affecting human health and climate. Fuels, burn conditions, and fire types vary across the United States, which may impact smoke composition and optical properties. We use the Hazard Mapping System to track smoke plumes for 10 years from 2008 to 2017, focusing on three U.S. regions: Southeast, Pacific West, and Southwest. Combining this geospatial data set with AErosol RObotic NETwork (AERONET) columnar data, and Interagency Monitoring of Protected Visual Environments (IMPROVE) network in situ observations, we define “smoke-influenced days” and derive the properties of smoke aerosol for April through September, encompassing the main fire seasons across the United States. We find in the IMPROVE surface measurement that the elemental carbon fraction of smoke in the Southeast is statistically different from and lower than that in the west, consistent with more-smoldering prescribed fires in the southeast. We find in the AERONET columnar observations that the mean single scattering albedo of smoke (at 675 nm) is lower in the two western regions ( 0.94) compared to the southeast ( 0.96), consistent with the differences in composition and fire types, which implies that the compositional differences at the surface may be representative of the column. Higher relative humidity in the southeast and less dust associated with smoke also appear to contribute to the higher smoke single scattering albedo relative to the west. Our results show that smoke properties vary regionally, with implications for models, data assimilation, and remote-sensing.

3. Beyond SOx reductions from shipping: assessing the impact of NOx and carbonaceous-particle controls on human health and climate

   Kelsey R. Bilsback, Deanna Kerry, Betty Croft, and 5 more authors

   Environmental Research Letters, Dec 2020

   Abs Article

   Historically, cargo ships have been powered by low-grade fossil fuels, which emit particles and particle-precursor vapors that impact human health and climate. We used a global chemical-transport model with online aerosol microphysics (GEOS-Chem-TOMAS) to estimate the aerosol health and climate impacts of four emission-control policies: (1) 85% reduction in sulfur oxide (SOx) emissions (Sulf); (2) 85% reduction in SOx and black carbon (BC) emissions (Sulf-BC); (3) 85% reduction in SOx, BC, and organic aerosol (OA) emissions (Sulf-BC-OA); and (4) 85% reduction in SOx, BC, OA, and nitrogen oxide (NOx) emissions (Sulf-BC-OA-NOx). The SOx reductions reflect the 0.5% fuel-sulfur cap implemented by the International Maritime Organization (IMO) on 1 January 2020. The other reductions represent realistic estimates of future emission-control policies. We estimate that these policies could reduce fine particulate matter (PM2.5)-attributable mortalities by 13 300 (Sulf) to 38 600 (Sulf-BC-OA-NOx) mortalities per year. These changes represent 0.3% and 0.8%, respectively, of annual PM2.5-attributable mortalities from anthropogenic sources. Comparing simulations, we estimate that adding the NOx cap has the greatest health benefit. In contrast to the health benefits, all scenarios lead to a simulated climate warming tendency. The combined aerosol direct radiative effect and cloud-albedo indirect effects (AIE) are between 27 mW m−2 (Sulf) and 41 mW m−2 (Sulf-BC-OA-NOx). These changes are about 2.1% (Sulf) to 3.2% (Sulf-BC-OA-NOx) of the total anthropogenic aerosol radiative forcing. The emission control policies examined here yield larger relative changes in the aerosol radiative forcing (2.1%–3.2%) than in health effects (0.3%–0.8%), because most shipping emissions are distant from populated regions. Valuation of the impacts suggests that these emissions reductions could produce much larger marginal health benefits (129–374 billion annually) than the marginal climate costs (12–17 billion annually).

4. Estimated Aerosol Health and Radiative Effects of the Residential Coal Ban in the Beijing-Tianjin-Hebei Region of China

   Kelsey R. Bilsback, Jill Baumgartner, Michael Cheeseman, and 8 more authors

   Aerosol and Air Quality Research, Dec 2020

   Abs Article

   ABSTRACT Particle-phase air pollution is a leading risk factor for premature death globally and impacts climate by scattering or absorbing radiation and changing cloud properties. Within the Beijing-Tianjin-Hebei region of China, where there are severe air quality problems, several municipalities have begun implementing a coal-to-electricity program that bans residential coal and provides subsidies for electricity and electric-powered heat pumps. We used GEOS-Chem to evaluate two complete residential coal-to-electricity transitions—a Beijing-off scenario and Beijing-Tianjin-Hebei-off scenario—each relative to a base case. We estimate that within China, the ambient fine particulate matter (PM2.5) reductions in the Beijing-off scenario could lead to 1,900 (95% CI: 1,200–2,700) premature deaths avoided annually, while the Beijing-Tianjin-Hebei-off scenario could lead to 13,700 (95% CI: 8,900–19,600) premature deaths avoided annually. Additionally, we estimate that the residential-coal-ban scenarios will result in a positive top-of-the-atmosphere aerosol direct radiative effect (DRE) (model domain average: Beijing-off: 0.023 W m–2; Beijing-Tianjin-Hebei-off: 0.30 W m–2) and a negligible cloud-albedo aerosol indirect effect (AIE) (Beijing-off: 0.0001 W m–2; Beijing-Tianjin-Hebei-off: 0.0027 W m–2). To evaluate the uncertainty of the radiative effects, we calculated the DRE under four black-carbon mixing-state assumptions and both the DRE and AIE assuming three different black-carbon-to-organic-aerosol (BC:OA) ratios for residential-coal emissions. Although the magnitude of our radiative forcing estimates varied across sensitivity cases, the domain average remained positive. When only considering the aerosol-related effects of the aforementioned coal-ban scenarios, we predict substantial health benefits, but do not anticipate a climate “co-benefit”, because removing aerosol emissions leads to a warming tendency. However, if the coal-to-electricity program results in less net greenhouse gas emissions due to the replacement heaters, the policy may be able to achieve health and climate “co-benefits”.

5. The Relationship Between MAIAC Smoke Plume Heights and Surface PM

   M. Cheeseman, B. Ford, J. Volckens, and 2 more authors

   Geophysical Research Letters, Dec 2020

   Abs Article

   Biomass burning is a source of fine particulate matter (PM2.5) air pollution, which adversely impacts human health. However, quantifying the health effects from biomass burning PM2.5 is difficult. Monitoring networks generally lack the spatial density needed to capture the heterogeneity of biomass burning smoke. Satellite aerosol optical depth (AOD) can be used to fill spatial gaps but does not distinguish surface-level aerosols. Plume height (PH) observations may provide constraints on the vertical distribution of smoke and its impact on surface concentrations. We assessed PH characteristics from Multi-Angle Implementation of Atmospheric Correction (MAIAC) and evaluated its correlation with colocated PM2.5 and AOD measurements. PH is generally highest over the western United States. The ratio PM2.5:AOD generally decreases with increasing PH:PBLH (planetary boundary layer height), showing that PH has the potential to refine surface PM2.5 estimates for collections of smoke events.

6. The relationship between monthly air pollution and violent crime across the United States

   Jesse Burkhardt, Jude Bayham, Ander Wilson, and 5 more authors

   Journal of Environmental Economics and Policy, Apr 2020

   Abs Article

   Recent evidence suggests a relationship between short-term pollution exposure and crime, with a particular emphasis on aggressive behavior. However, the previous analyses are limited in geographic scope. In this paper, we estimate the effect of fine particulate air pollution (PM2.5) exposure on crime across 99% of counties in the contiguous United States. We combine monthly data on crime, PM2.5, and satellite-derived smoke plumes for a ten-year period. We use adjusted satellite-based landscape fire smoke plume data as an instrument for overall changes in PM2.5. Our findings are consistent with previous research and suggest that increases in PM2.5 raise violent crime rates, and specifically assaults. Our results indicate the effect is relatively homogeneous across the U.S. However, we find the effect is positively correlated with county median age, suggesting older populations are more susceptible to changes in air pollution. Our results indicate a need for more research on the physiological and social mechanisms behind the measured effects.

7. The association between wildfire smoke exposure and asthma-specific medical care utilization in Oregon during the 2013 wildfire season

   Ryan W. Gan, Jingyang Liu, Bonne Ford, and 8 more authors

   Journal of Exposure Science & Environmental Epidemiology, Jul 2020

   Abs Article

   Wildfire smoke (WFS) increases the risk of respiratory hospitalizations. We evaluated the association between WFS and asthma healthcare utilization (AHCU) during the 2013 wildfire season in Oregon. WFS particulate matter ≤ 2.5 μm in diameter (PM2.5) was estimated using a blended model of in situ monitoring, chemical transport models, and satellite-based data. Asthma claims and place of service were identified from Oregon All Payer All Claims data from 1 May 2013 to 30 September 2013. The association with WFS PM2.5 was evaluated using time-stratified case-crossover designs. The maximum WFS PM2.5 concentration during the study period was 172 µg/m3. A 10 µg/m3 increase in WFS increased risk in asthma diagnosis at emergency departments (odds ratio [OR]: 1.089, 95% confidence interval [CI]: 1.043–1.136), office visit (OR: 1.050, 95% CI: 1.038–1.063), and outpatient visits (OR: 1.065, 95% CI: 1.029–1.103); an association was observed with asthma rescue inhaler medication fills (OR: 1.077, 95% CI: 1.065–1.088). WFS increased the risk for asthma morbidity during the 2013 wildfire season in Oregon. Communities impacted by WFS could see increases in AHCU for tertiary, secondary, and primary care.

8. Global Estimates and Long-Term Trends of Fine Particulate Matter Concentrations (1998–2018)

   Melanie S. Hammer, Aaron Donkelaar, Chi Li, and 15 more authors

   Environmental Science & Technology, Jul 2020

   Abs Article

   Exposure to outdoor fine particulate matter (PM2.5) is a leading risk factor for mortality. We develop global estimates of annual PM2.5 concentrations and trends for 1998–2018 using advances in satellite observations, chemical transport modeling, and ground-based monitoring. Aerosol optical depths (AODs) from advanced satellite products including finer resolution, increased global coverage, and improved long-term stability are combined and related to surface PM2.5 concentrations using geophysical relationships between surface PM2.5 and AOD simulated by the GEOS-Chem chemical transport model with updated algorithms. The resultant annual mean geophysical PM2.5 estimates are highly consistent with globally distributed ground monitors (R2 = 0.81; slope = 0.90). Geographically weighted regression is applied to the geophysical PM2.5 estimates to predict and account for the residual bias with PM2.5 monitors, yielding even higher cross validated agreement (R2 = 0.90–0.92; slope = 0.90–0.97) with ground monitors and improved agreement compared to all earlier global estimates. The consistent long-term satellite AOD and simulation enable trend assessment over a 21 year period, identifying significant trends for eastern North America (−0.28 ± 0.03 μg/m3/yr), Europe (−0.15 ± 0.03 μg/m3/yr), India (1.13 ± 0.15 μg/m3/yr), and globally (0.04 ± 0.02 μg/m3/yr). The positive trend (2.44 ± 0.44 μg/m3/yr) for India over 2005–2013 and the negative trend (−3.37 ± 0.38 μg/m3/yr) for China over 2011–2018 are remarkable, with implications for the health of billions of people.

9. Using Low-Cost Measurement Systems to Investigate Air Quality: A Case Study in Palapye, Botswana

   William Lassman, Jeffrey R. Pierce, Evelyn J. Bangs, and 6 more authors

   Atmosphere, Jun 2020

   Abs Article

   Exposure to particulate air pollution is a major cause of mortality and morbidity worldwide. In developing countries, the combustion of solid fuels is widely used as a source of energy, and this process can produce exposure to harmful levels of particulate matter with diameters smaller than 2.5 microns (PM2.5). However, as countries develop, solid fuel may be replaced by centralized coal combustion, and vehicles burning diesel and gasoline may become common, changing the concentration and composition of PM2.5, which ultimately changes the population health effects. Therefore, there is a continuous need for in-situ monitoring of air pollution in developing nations, both to estimate human exposure and to monitor changes in air quality. In this study, we present measurements from a 5-week field experiment in Palapye, Botswana. We used a low-cost, highly portable instrument package to measure surface-based aerosol optical depth (AOD), real-time surface PM2.5 concentrations using a third-party optical sensor, and time-integrated PM2.5 concentration and composition by collecting PM2.5 onto Teflon filters. Furthermore, we employed other low-cost measurements of real-time black carbon and time-integrated ammonia to help interpret the observed PM2.5 composition and concentration information during the field experiment. We found that the average PM2.5 concentration (9.5 µg∙m−3) was below the World Health Organization (WHO) annual limit, and this concentration closely agrees with estimates from the Global Burden of Disease (GBD) report estimates for this region. Sulfate aerosol and carbonaceous aerosol, likely from coal combustion and biomass burning, respectively, were the main contributors to PM2.5 by mass (33% and 27% of total PM2.5 mass, respectively). While these observed concentrations were on average below WHO guidelines, we found that the measurement site experienced higher concentrations of aerosol during first half our measurement period (14.5 µg∙m−3), which is classified as “moderately unhealthy” according to the WHO standard.

2019

1. A national burden assessment of estimated pediatric asthma emergency department visits that may be attributed to elevated ozone levels associated with the presence of smoke

   Jacob R. Pratt, Ryan W. Gan, Bonne Ford, and 4 more authors

   Environmental Monitoring and Assessment, Jun 2019

   Abs Article

   Asthma is the most common pediatric disease in the USA. It has been consistently demonstrated that asthma symptoms are exacerbated by exposure to ozone. Ozone (O3) is a secondary pollutant produced when volatile organic compounds (VOCs) are oxidized in the atmosphere in the presence of nitrogen oxides (NOx). At ground level, elevated ozone is typically formed as a result of human activities. However, wildfires represent an additional source of ozone precursors. Recent evidence suggests that smoke can increase ozone concentrations. We estimated the number of excess asthma-related emergency department (ED) visits in children with asthma that may be attributed to elevated ozone associated with smoke (EOAS) in the USA. We conducted a quantitative burden assessment (BA) using a Monte Carlo approach to estimate the median number of excess pediatric asthma ED visits that may be attributed to EOAS among children with asthma in the continental USA between 2005 and 2014, as well as 95% confidence bounds (95% CB). We estimated that a median of 2403 (95% CB 235–5382) pediatric asthma ED visits could be attributed to EOAS exposure between 2005 and 2014 in the continental USA. Furthermore, the impact of EOAS on estimated asthma ED visits was greatest in the eastern half of the continental USA. We found a significant increase in pediatric asthma ED visits that may be attributed to exposure to EOAS. EOAS may have a measurable negative impact on children with asthma in the USA.

2. The effect of pollution on crime: Evidence from data on particulate matter and ozone

   Jesse Burkhardt, Jude Bayham, Ander Wilson, and 6 more authors

   Journal of Environmental Economics and Management, Nov 2019

   Abs Article

   We estimate the effect of short-term air pollution exposure (PM2.5 and ozone) on several categories of crime, with a particular emphasis on aggressive behavior. To identify this relationship, we combine detailed daily data on crime, air pollution, and weather for an eight-year period across the United States. Our primary identification strategy employs extremely high dimensional fixed effects and we perform a series of robustness checks to address confounding variation between temperature and air pollution. We find a robust positive effect of increased air pollution on violent crimes, and specifically assaults, but no relationship between increases in air pollution and property crimes. The effects are present in and out of the home, at levels well below Ambient Air Pollution Standards, and PM2.5 effects are strongest at lower temperatures. The results suggest that a 10% reduction in daily PM2.5 and ozone could save $1.4 billion in crime costs per year, a previously overlooked cost associated with pollution.

3. The Associations Between Clinical Respiratory Outcomes and Ambient Wildfire Smoke Exposure Among Pediatric Asthma Patients at National Jewish Health, 2012–2015

   Ettie M. Lipner, Katelyn O’Dell, Steven J. Brey, and 4 more authors

   GeoHealth, Nov 2019

   Abs Article

   Wildfires are a growing threat in the United States. At a population level, exposure to ambient wildfire smoke is known to be associated with severe asthma outcomes such as hospitalizations. However, little work has been done on subacute clinical asthma outcomes, especially in sensitive populations. This study retrospectively investigated associations between ambient wildfire smoke exposure and measures of lung function and asthma control, Forced Expiratory Volume in 1 Second (FEV1) and the Asthma Control Test (ACT) and Children’s Asthma Control Test (CACT) test scores, during nonurgent clinic visits. The study population consisted of pediatric asthma patients (ages 4–21; n = 1,404 for FEV1 and n = 395 for ACT/CACT) at National Jewish Health, a respiratory referral hospital in Denver, Colorado, and therefore represents a more severe asthma phenotype than the general pediatric asthma population. Wildfire smoke-related PM2.5 at patients’ residential ZIP codes was characterized using satellite-derived smoke polygons from NOAA’s Hazard Mapping System combined with kriging of ground-based U.S. EPA monitors. Mixed effect models were used to estimate associations between clinical outcomes and smoke PM2.5 exposure, controlling for known risk factors and confounders. Among older children aged 12–21 we found that wildfire PM2.5 was associated with lower FEV1 the next day but higher FEV1 the day after. We found no associations between wildfire PM2.5 and FEV1 in younger children or between wildfire PM2.5 and asthma control measured by the ACT/CACT in all ages. We speculate that rescue medication usage by older children may decrease respiratory symptoms caused by wildfire smoke.

4. Impact of Wildfire Smoke on Adverse Pregnancy Outcomes in Colorado, 2007-2015

   Mona Abdo, Isabella Ward, Katelyn O’Dell, and 4 more authors

   International Journal of Environmental Research and Public Health, Nov 2019

   Abs Article

   Colorado is regularly impacted by long-range transport of wildfire smoke from upwind regions. This smoke is a major source of ambient PM2.5. Maternal exposure to total PM2.5 during pregnancy has been linked to decreased birth weight and other adverse outcomes, although the impact of wildfire smoke contribution has only recently been investigated. The objective of this study was to estimate associations between adverse pregnancy outcomes and ambient wildfire smoke PM2.5. Wildfire smoke PM2.5 exposures were estimated using a previously published method incorporating ground-based monitors and remote sensing data. Logistic regression models stratified by ZIP code and mixed models with random intercept by ZIP code were used to test for associations. The primary outcomes of interest were preterm birth and birth weight. Secondary outcomes included gestational hypertension, gestational diabetes, neonatal intensive care unit admission, assisted ventilation, small for gestational age, and low birth weight. Exposure to wildfire smoke PM2.5 over the full gestation and during the second trimester were positively associated with pre-term birth (OR = 1.076 (μg/m3)-1 [95% CI = 1.016, 1.139; p = 0.013] and 1.132 (μg/m3)-1 [95% CI = 1.088, 1.178]; p \textless 0.0001, respectively), while exposure during the first trimester was associated with decreased birth weight (-5.7 g/(μg/m3) [95% CI: -11.1, -0.4; p = 0.036]). Secondary outcomes were mixed.

5. Contribution of Wildland-Fire Smoke to US PM2.5 and Its Influence on Recent Trends

   Katelyn O’Dell, Bonne Ford, Emily V. Fischer, and 1 more author

   Environmental Science & Technology, Feb 2019

   Abs Article

   Seasonal-mean concentrations of particulate matter with diameters smaller than 2.5 μm (PM2.5) have been decreasing across the United States (US) for several decades, with large reductions in spring and summer in the eastern US. In contrast, summertime-mean PM2.5 in the western US has not significantly decreased. Wildfires, a large source of summertime PM2.5 in the western US, have been increasing in frequency and burned area in recent decades. Increases in extreme PM2.5 events attributable to wildland fires have been observed in wildfire-prone regions, but it is unclear how these increases impact trends in seasonal-mean PM2.5. Using two distinct methods, (1) interpolated surface observations combined with satellite-based smoke plume estimates and (2) the GEOS-Chem chemical transport model (CTM), we identify recent trends (2006–2016) in summer smoke, nonsmoke, and total PM2.5 across the US. We observe significant decreases in nonsmoke influenced PM2.5 in the western US and find increases in summer-mean smoke PM2.5 in fire-prone regions, although these are not statistically significant due to large interannual variability in the abundance of smoke. These results indicate that without the influence of wildland fires, we would expect to have observed improvements in summer fine particle pollution in the western US but likely weaker improvements than those observed in the eastern US.

6. A low-cost monitor for simultaneous measurement of fine particulate matter and aerosol optical depth – Part 1: Specifications and testing

   Eric A. Wendt, Casey W. Quinn, Daniel D. Miller-Lionberg, and 7 more authors

   Atmospheric Measurement Techniques, Oct 2019

   Abs Article

   Globally, fine particulate matter (PM2.5) air pollution is a leading contributor to death, disease, and environmental degradation. Satellite-based measurements of aerosol optical depth (AOD) are used to estimate PM2.5 concentrations across the world, but the relationship between satellite-estimated AOD and ground-level PM2.5 is uncertain. Sun photometers measure AOD from the Earth’s surface and are often used to improve satellite data; however, reference-grade photometers and PM2.5 monitors are expensive and rarely co-located. This work presents the development and validation of the aerosol mass and optical depth (AMOD) sampler, an inexpensive and compact device that simultaneously measures PM2.5 mass and AOD. The AMOD utilizes a low-cost light-scattering sensor in combination with a gravimetric filter measurement to quantify ground-level PM2.5. Aerosol optical depth is measured using optically filtered photodiodes at four discrete wavelengths. Field validation studies revealed agreement within 10 % for AOD values measured between co-located AMOD and AErosol RObotics NETwork (AERONET) monitors and for PM2.5 mass measured between co-located AMOD and EPA Federal Equivalent Method (FEM) monitors. These results demonstrate that the AMOD can quantify AOD and PM2.5 accurately at a fraction of the cost of existing reference monitors.

7. A low-cost monitor for measurement of fine particulate matter and aerosol optical depth – Part 2: Citizen-science pilot campaign in northern Colorado

   Bonne Ford, Jeffrey R. Pierce, Eric Wendt, and 9 more authors

   Atmospheric Measurement Techniques, Dec 2019

   Abs Article

   A pilot field campaign was conducted in the fall and winter of 2017 in northern Colorado to test the deployment of the Aerosol Mass and Optical Depth (AMOD) instrument as part of the Citizen-Enabled Aerosol Measurements for Satellites (CEAMS) network. Citizen scientists were recruited to set up the device to take filter and optical measurements of aerosols in their backyards. The goal of the network is to provide more surface particulate matter and aerosol optical depth (AOD) measurements to increase the spatial and temporal resolution of ratios of fine particulate matter (PM2.5) to AOD and to improve satellite-based estimates of air quality. Participants collected 65 filters and 160 multi-wavelength AOD measurements, from which 109 successful PM2.5 : AOD ratios were calculated. We show that PM2.5, AOD, and their ratio (PM2.5 : AOD) often vary substantially over relatively short spatial scales; this spatial variation is not typically resolved by satellite- and model-based PM2.5 exposure estimates. The success of the pilot campaign suggests that citizen-science networks are a viable means for providing new insight into surface air quality. We also discuss lessons learned and AMOD design modifications, which will be used in future wider deployments of the CEAMS network.

2018

1. Future Fire Impacts on Smoke Concentrations, Visibility, and Health in the Contiguous United States

   B. Ford, M. Val Martin, S. E. Zelasky, and 4 more authors

   GeoHealth, Dec 2018

   Abs Article

   Fine particulate matter (PM2.5) from U.S. anthropogenic sources is decreasing. However, previous studies have predicted that PM2.5 emissions from wildfires will increase in the midcentury to next century, potentially offsetting improvements gained by continued reductions in anthropogenic emissions. Therefore, some regions could experience worse air quality, degraded visibility, and increases in population-level exposure. We use global climate model simulations to estimate the impacts of changing fire emissions on air quality, visibility, and premature deaths in the middle and late 21st century. We find that PM2.5 concentrations will decrease overall in the contiguous United States (CONUS) due to decreasing anthropogenic emissions (total PM2.5 decreases by 3% in Representative Concentration Pathway [RCP] 8.5 and 34% in RCP4.5 by 2100), but increasing fire-related PM2.5 (fire-related PM2.5 increases by 55% in RCP4.5 and 190% in RCP8.5 by 2100) offsets these benefits and causes increases in total PM2.5 in some regions. We predict that the average visibility will improve across the CONUS, but fire-related PM2.5 will reduce visibility on the worst days in western and southeastern U.S. regions. We estimate that the number of deaths attributable to total PM2.5 will decrease in both the RCP4.5 and RCP8.5 scenarios (from 6% to 4–5%), but the absolute number of premature deaths attributable to fire-related PM2.5 will double compared to early 21st century. We provide the first estimates of future smoke health and visibility impacts using a prognostic land-fire model. Our results suggest the importance of using realistic fire emissions in future air quality projections.

2017

1. Status update: is smoke on your mind? Using social media to assess smoke exposure

   Bonne Ford, Moira Burke, William Lassman, and 2 more authors

   Atmospheric Chemistry and Physics, Jun 2017

   Abs Article

   \textlessp\textgreater\textlessstrong\textgreaterAbstract.\textless/strong\textgreater Exposure to wildland fire smoke is associated with negative effects on human health. However, these effects are poorly quantified. Accurately attributing health endpoints to wildland fire smoke requires determining the locations, concentrations, and durations of smoke events. Most current methods for assessing these smoke events (ground-based measurements, satellite observations, and chemical transport modeling) are limited temporally, spatially, and/or by their level of accuracy. In this work, we explore using daily social media posts from Facebook regarding smoke, haze, and air quality to assess population-level exposure for the summer of 2015 in the western US. We compare this de-identified, aggregated Facebook dataset to several other datasets that are commonly used for estimating exposure, such as satellite observations (MODIS aerosol optical depth and Hazard Mapping System smoke plumes), daily (24 h) average surface particulate matter measurements, and model-simulated (WRF-Chem) surface concentrations. After adding population-weighted spatial smoothing to the Facebook data, this dataset is well correlated (\textitR^\textrm2 generally above 0.5) with the other methods in smoke-impacted regions. The Facebook dataset is better correlated with surface measurements of PM_\textrm2. 5 at a majority of monitoring sites (163 of 293 sites) than the satellite observations and our model simulation. We also present an example case for Washington state in 2015, for which we combine this Facebook dataset with MODIS observations and WRF-Chem-simulated PM_\textrm2. 5 in a regression model. We show that the addition of the Facebook data improves the regression model’s ability to predict surface concentrations. This high correlation of the Facebook data with surface monitors and our Washington state example suggests that this social-media-based proxy can be used to estimate smoke exposure in locations without direct ground-based particulate matter measurements.\textless/p\textgreater

2. Spatial and Temporal Estimates of Population Exposure to Wildfire Smoke during the Washington State 2012 Wildfire Season Using Blended Model, Satellite, and In-Situ Data

   William Lassman, Bonne Ford, Ryan W. Gan, and 4 more authors

   GeoHealth, Jan 2017

   Abs Article

   In the western U.S., smoke from wild and prescribed fires can severely degrade air quality. Due to changes in climate and land-management, wildfires have increased in frequency and severity, and this trend is expected to continue. Consequently, wildfires are expected to become an increasingly important source of air pollutants in the western U.S. Hence, there is a need to develop a quantitative understanding of wildfire-smoke-specific health effects. A necessary step in this process is to determine who was exposed to wildfire smoke, the concentration of the smoke during exposure, and the duration of the exposure. Three different tools have been used in past studies to assess exposure to wildfire smoke: in-situ measurements, satellite-based observations, and chemical-transport model (CTM) simulations. Each of these exposure-estimation tools have associated strengths and weakness. We investigate the utility of blending these tools together to produce estimates of PM2.5 exposure from wildfire smoke during the Washington 2012 fire season. For blending, we use a ridge-regression model and a geographically weighted ridge-regression model. We evaluate the performance of the three individual exposure-estimate techniques and the two blended techniques using leave-one-out cross-validation. We find that predictions based on in-situ monitors are more accurate for this particular fire season than the CTM simulations and satellite-based observations because of the large number of monitors present; therefore, blending provides only marginal improvements above the in-situ observations. However, we show that in hypothetical cases with fewer surface monitors, the two blending techniques can produce substantial improvement over any of the individual tools. This article is protected by copyright. All rights reserved.

3. Comparison of wildfire smoke estimation methods and associations with cardiopulmonary-related hospital admissions

   Ryan W. Gan, Bonne Ford, William Lassman, and 6 more authors

   GeoHealth, Jan 2017

   Abs Article

   Climate forecasts predict an increase in frequency and intensity of wildfires. Associations between health outcomes and population exposure to smoke from Washington 2012 wildfires were compared using surface monitors, chemical-weather models, and a novel method blending three exposure information sources. The association between smoke particulate matter ≤2.5 μm in diameter (PM2.5) and cardiopulmonary hospital admissions occurring in Washington from 1 July to 31 October 2012 was evaluated using a time-stratified case-crossover design. Hospital admissions aggregated by ZIP code were linked with population-weighted daily average concentrations of smoke PM2.5 estimated using three distinct methods: a simulation with the Weather Research and Forecasting with Chemistry (WRF-Chem) model, a kriged interpolation of PM2.5 measurements from surface monitors, and a geographically weighted ridge regression (GWR) that blended inputs from WRF-Chem, satellite observations of aerosol optical depth, and kriged PM2.5. A 10 μg/m3 increase in GWR smoke PM2.5 was associated with an 8% increased risk in asthma-related hospital admissions (odds ratio (OR): 1.076, 95% confidence interval (CI): 1.019–1.136); other smoke estimation methods yielded similar results. However, point estimates for chronic obstructive pulmonary disease (COPD) differed by smoke PM2.5 exposure method: a 10 μg/m3 increase using GWR was significantly associated with increased risk of COPD (OR: 1.084, 95%CI: 1.026–1.145) and not significant using WRF-Chem (OR: 0.986, 95%CI: 0.931–1.045). The magnitude (OR) and uncertainty (95%CI) of associations between smoke PM2.5 and hospital admissions were dependent on estimation method used and outcome evaluated. Choice of smoke exposure estimation method used can impact the overall conclusion of the study.

2016

1. Exploring the uncertainty associated with satellite-based estimates of premature mortality due to exposure to fine particulate matter

   B. Ford, and C. L. Heald

   Atmos. Chem. Phys., Mar 2016

   Abs Article

   The negative impacts of fine particulate matter (PM2.5) exposure on human health are a primary motivator for air quality research. However, estimates of the air pollution health burden vary considerably and strongly depend on the data sets and methodology. Satellite observations of aerosol optical depth (AOD) have been widely used to overcome limited coverage from surface monitoring and to assess the global population exposure to PM2.5 and the associated premature mortality. Here we quantify the uncertainty in determining the burden of disease using this approach, discuss different methods and data sets, and explain sources of discrepancies among values in the literature. For this purpose we primarily use the MODIS satellite observations in concert with the GEOS-Chem chemical transport model. We contrast results in the United States and China for the years 2004–2011. Using the Burnett et al. (2014) integrated exposure response function, we estimate that in the United States, exposure to PM2.5 accounts for approximately 2 % of total deaths compared to 14 % in China (using satellite-based exposure), which falls within the range of previous estimates. The difference in estimated mortality burden based solely on a global model vs. that derived from satellite is approximately 14 % for the US and 2 % for China on a nationwide basis, although regionally the differences can be much greater. This difference is overshadowed by the uncertainty in the methodology for deriving PM2.5 burden from satellite observations, which we quantify to be on the order of 20 % due to uncertainties in the AOD-to-surface-PM2.5 relationship, 10 % due to the satellite observational uncertainty, and 30 % or greater uncertainty associated with the application of concentration response functions to estimated exposure.

2. Global burden of mortalities due to chronic exposure to ambient PM2.5 from open combustion of domestic waste

   John K. Kodros, Christine Wiedinmyer, Bonne Ford, and 4 more authors

   Environmental Research Letters, Dec 2016

   Abs Article

   Uncontrolled combustion of domestic waste has been observed in many countries, creating concerns for air quality; however, the health implications have not yet been quantified. We incorporate the Wiedinmyer et al (2014 Environ. Sci. Technol. 48 9523–30) emissions inventory into the global chemical-transport model, GEOS-Chem, and provide a first estimate of premature adult mortalities from chronic exposure to ambient PM2.5 from uncontrolled combustion of domestic waste. Using the concentration-response functions (CRFs) of Burnett et al (2014 Environ. Health Perspect. 122 397–403), we estimate that waste-combustion emissions result in 270 000 (5th–95th: 213 000–328 000) premature adult mortalities per year. The confidence interval results only from uncertainty in the CRFs and assumes equal toxicity of waste-combustion PM2.5 to all other PM2.5 sources. We acknowledge that this result is likely sensitive to choice of chemical-transport model, CRFs, and emission inventories. Our central estimate equates to 9% of adult mortalities from exposure to ambient PM2.5 reported in the Global Burden of Disease Study 2010. Exposure to PM2.5 from waste combustion increases the risk of premature mortality by more than 0.5% for greater than 50% of the population. We consider sensitivity simulations to uncertainty in waste-combustion emission mass, the removal of waste-combustion emissions, and model resolution. A factor-of-2 uncertainty in waste-combustion PM2.5 leads to central estimates ranging from 138 000 to 518 000 mortalities per year for factors-of-2 reductions and increases, respectively. Complete removal of waste combustion would only avoid 191 000 (5th–95th: 151 000–224 000) mortalities per year (smaller than the total contributed premature mortalities due to nonlinear CRFs). Decreasing model resolution from 2° × 2.5° to 4° × 5° results in 16% fewer mortalities attributed to waste-combustion PM2.5, and over Asia, decreasing resolution from 0.5° × 0.666° to 2° × 2.5° results in 21% fewer mortalities attributed to waste-combustion PM2.5. Owing to coarse model resolution, our global estimates of premature mortality from waste-combustion PM2.5 are likely a lower bound.

2013

1. Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

   B. Ford, and C. L. Heald

   Atmos. Chem. Phys., Sep 2013

   Abs Article

   We investigate the seasonality in aerosols over the Southeastern United States using observations from several satellite instruments (MODIS, MISR, CALIOP) and surface network sites (IMPROVE, SEARCH, AERONET). We find that the strong summertime enhancement in satellite-observed aerosol optical depth (AOD) (factor 2–3 enhancement over wintertime AOD) is not present in surface mass concentrations (25–55% summertime enhancement). Goldstein et al. (2009) previously attributed this seasonality in AOD to biogenic organic aerosol; however, surface observations show that organic aerosol only accounts for ∼35% of fine particulate matter (smaller than 2.5 μm in aerodynamic diameter, PM2.5) and exhibits similar seasonality to total surface PM2.5. The GEOS-Chem model generally reproduces these surface aerosol measurements, but underrepresents the AOD seasonality observed by satellites. We show that seasonal differences in water uptake cannot sufficiently explain the magnitude of AOD increase. As CALIOP profiles indicate the presence of additional aerosol in the lower troposphere (below 700 hPa), which cannot be explained by vertical mixing, we conclude that the discrepancy is due to a missing source of aerosols above the surface layer in summer.

2. A decadal satellite analysis of the origins and impacts of smoke in Colorado

   M. Val Martin, C. L. Heald, B. Ford, and 2 more authors

   Atmospheric Chemistry and Physics, Mar 2013

   Abs Article

   We analyze the record of aerosol optical depth (AOD) measured by the MODerate resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite in combination with surface PM2.5 to investigate the impact of fires on aerosol loading and air quality over Colorado from 2000 to 2012, and to evaluate the contribution of local versus transported smoke. Fire smoke contributed significantly to the AOD levels observed over Colorado. During the worst fire seasons of 2002 and 2012, average MODIS AOD over the Colorado Front Range corridor were 20–50% larger than the other 11 yr studied. Surface PM2.5 was also unusually elevated during fire events and concentrations were in many occasions above the daily National Ambient Air Quality Standard (35 μg m−3) and even reached locally unhealthy levels (> 100 μg m−3) over populated areas during the 2012 High Park fire and the 2002 Hayman fire. Over the 13 yr examined, long-range transport of smoke from northwestern US and even California (> 1500 km distance) occurred often and affected AOD and surface PM2.5. During most of the transport events, MODIS AOD and surface PM2.5 were reasonable correlated (r2 = 0.2–0.9), indicating that smoke subsided into the Colorado boundary layer and reached surface levels. However, that is not always the case since at least one event of AOD enhancement was disconnected from the surface (r2<0.01 and low PM2.5 levels). Observed plume heights from the Multi-angle Imaging SpectroRadiometer (MISR) satellite instrument and vertical aerosol profiles measured by the space-based Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) showed a complex vertical distribution of smoke emitted by the High Park fire in 2012. Smoke was detected from a range of 1.5 to 7.5 km altitude at the fire origin and from ground levels to 12.3 km altitude far away from the source. The variability of smoke altitude as well as the local meteorology were key in determining the aerosol loading and air quality over the Colorado Front Range region. Our results underline the importance of accurate characterization of the vertical distribution of smoke for estimating the air quality degradation associated with fire activity and its link to human health.

2012

1. North African dust export and deposition: A satellite and model perspective

   D. A. Ridley, C. L. Heald, and B. Ford

   Journal of Geophysical Research, Jan 2012

   Abs Article

   We use a suite of satellite observations (Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), Cloud-Aerosol Lidar With Orthogonal Polarization (CALIOP)) to investigate the processes of long-range transport of dust represented in the global GEOS-Chem model in 2006–2008. A multiyear mean of African dust transport is developed and used to test the representation of the variability in the model. We find that both MODIS and MISR correlate well with the majority of Aerosol Robotic Network observations in the region (r \textgreater 0.8). However, MODIS aerosol optical depth (AOD) appears to be biased low (\textgreater0.05) relative to MISR in Saharan regions during summer. We find that GEOS-Chem captures much of the variability in AOD when compared with MISR and MODIS (r \textgreater 0.6) and represents the vertical structure in aerosol extinction over outflow regions well when compared to CALIOP. Including a realistic representation of the submicron-size distribution of dust reduces simulated AOD by ∼25% over North Africa and improves agreement with observations. The lifetime of the simulated dust is typically a few days (25%–50%) shorter than inferred from MODIS observations, suggesting overvigorous wet removal, confirmed by comparison with rain rate observations from the Tropical Rainfall Measuring Mission satellite. The simulation captures the seasonality of deposition in Florida and the observed magnitude and variability of dust concentrations at Barbados from 2006 to 2008 (r = 0.74), indicating a good simulation of the impacts of North African dust on air quality in North America. We estimate that 218 ± 48 Tg of dust is annually deposited into the Atlantic and calculate a lower estimate for the dust deposited in the Caribbean and Amazon to be 26 ± 5 Tg yr−1 and 17 ± 5 Tg yr−1, respectively. This suggests that the dust deposition in the Amazon derived from satellites may be an upper limit.

2. An A-train and model perspective on the vertical distribution of aerosols and CO in the Northern Hemisphere

   Bonne Ford, and Colette L. Heald

   Journal of Geophysical Research, Mar 2012

   Abs Article

   We use A-train satellite observations of aerosols and carbon monoxide (CO) (CALIOP, MODIS, and TES) with GEOS-Chem model simulations to analyze long range transport in the Northern Hemisphere over 3 years (December 2006–November 2009), with a focus on the vertical distribution of pollutants. GEOS-Chem underestimates TES observations of CO in all seasons (\textless25%) except winter. MODIS and GEOS-Chem aerosol optical depths (AOD) are both generally biased high in comparison with CALIOP (0.042 over land/0.036 over ocean and 0.016 over land/−0.0071 over ocean, respectively; for spring seasons, but similar results for all seasons). Comparisons between GEOS-Chem and CALIOP improve when the CALIOP detection limits are accounted for, and the bias over land in particular is reduced (0.010). However, we find that GEOS-Chem with applied detection limits still overestimates the CALIOP observations of aerosol extinction over sources in Asia and Europe, but underestimates in marine environments and over North America in spring and summer. Vertical cross-sections indicate that GEOS-Chem may be removing aerosol too efficiently in the boundary layer in addition to underestimating marine aerosol sources. We show that mimicking the single aerosol type per layer retrieval of CALIOP with GEOS-Chem could lower simulated AOD by 10–30% at midlatitudes. TES and CALIOP observations confirm that while CO is efficiently transported aloft (only 12% of the CO column is within the planetary boundary layer (PBL) on average), the efficient removal of aerosol limits export and subsequent transport with over 50% of observed aerosol extinction occurring within the PBL.

2010

1. An evaluation of the interaction of morning residual layer and afternoon mixed layer ozone in Houston using ozonesonde data

   Gary A. Morris, Bonne Ford, Bernhard Rappenglück, and 4 more authors

   Atmospheric Environment, Oct 2010

   Abs Article

   The Tropospheric Ozone Pollution Project (TOPP) launched \textgreater220 ozonesondes in Houston (July 2004–June 2008) providing examples of pollution transported into, re-circulated within, and exported from the Houston area. Fifty-one launches occurred during the Texas Air Quality Study (TexAQS) II and the summer portion of IONS-06 (INTEX [Intercontinental Transport Experiment] Ozonesonde Network Study). On 11 days during TexAQS II and on 8 other occasions, ozonesondes were launched both at dawn and in the afternoon. Analysis of these “intensive” launch sequences shows that morning residual layer (RL) ozone concentrations ([O3]) explained 60–70% of the variability found in the afternoon mixed layer (ML). Furthermore, maximum RL [O3] is nearly identical to the mean ML [O3] from the previous afternoon (morning minus afternoon = −1.6 ± 8.4 ppbv). During TexAQS II, mean [O3] below 1.3 km (the mean ML height from ozonesonde data) increased from 37 ± 22 ppbv in the morning to 74 ± 18 ppbv in the afternoon, suggesting an average net local daily O3 production of ∼500–900 tons over the metropolitan Houston area.