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Overwhelming evidence has shown that, from the Industrial Revolution to the present, human activities influence ground-level ozone (O 3 ) concentrations. Past studies demonstrate links between O 3 exposure and health. However, knowledge gaps remain in our understanding concerning the impacts of climate change mitigation policies on O 3 concentrations and health. Using a hybrid downscaling approach, we evaluated the separate impact of climate change and emission control policies on O 3 levels and associated excess mortality in the US in the 2050s under two Representative Concentration Pathways (RCPs). We show that, by the 2050s, under RCP4.5, increased O 3 levels due to combined climate change and emission control policies, could contribute to an increase of approximately 50 premature deaths annually nationwide in the US. The biggest impact, however, is seen under RCP8.5, where rises in O 3 concentrations are expected to result in over 2,200 additional premature deaths annually. The largest increases in O 3 are seen in RCP8.5 in the Northeast, the Southeast, the Central, and the West regions of the US. Additionally, when O 3 increases are examined by climate change and emissions contributions separately, the benefits of emissions mitigation efforts may significantly outweigh the effects of climate change mitigation policies on O 3 -related mortality. [ABSTRACT FROM AUTHOR]

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 (PM 2.5). However, relatively few epidemiologic studies focus on the health impacts of wildfire smoke PM 2.5 compared with the number of studies focusing on total PM 2.5 exposure. We estimated the associations between cardiorespiratory acute events and exposure to smoke PM 2.5 in Colorado using a novel exposure model to separate smoke PM 2.5 from background ambient PM 2.5 levels. 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 PM 2.5 and non-smoke PM 2.5 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 PM 2.5 and non-smoke PM 2.5 for overall and age-stratified outcomes using 2-day averaging windows for cardiovascular disease and 3-day windows for respiratory disease. Per 1 μg/m3 increase in fire smoke PM 2.5 , 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 PM 2.5. Associations with non-smoke PM 2.5 were null for all outcomes. Positive age-specific associations related to smoke PM 2.5 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. This is the first multi-year, high-resolution epidemiologic study to incorporate statistical and chemical transport modeling methods to estimate PM 2.5 exposure due to wildfires. Our results allow for a more precise assessment of the population health impact of wildfire-related PM 2.5 exposure in a changing climate. • Wildfire PM 2.5 associated with asthma and combined respiratory diseases • Children displayed significant associations between smoke exposure and asthma. • Wildfire PM 2.5 associated with asthma, bronchitis, combined respiratory in adults • Older adults did not exhibit associations with examined respiratory outcomes. • Cardiovascular outcomes not associated in grouped or stratified analysis [ABSTRACT FROM AUTHOR]

[Display omitted] • Prescribed burns are a major source of air pollution in the southeastern US. • A total of 25.1 million acres of land was treated with prescribed burns in the ten southeastern US states during 2013–2020. • About 15 % of ambient PM 2.5 in Alabama, Florida, Georgia, Mississippi, and South Carolina originates from prescribed burns. • Prescribed burns lead to an average 1.0 % increase in ambient MDA8-O 3 in Alabama, Florida, Georgia, and South Carolina. • Prescribed burn PM 2.5 and MDA8-O 3 respectively lead to 20,416 and 1,332 premature deaths in the ten southeastern US states. Ambient air quality across the southeastern US has improved substantially in recent decades. However, emissions from prescribed burns remain high, which may pose a substantial health threat. We employed a multistage modeling framework to estimate year-round, long-term effects of prescribed burns on air quality and premature deaths. The framework integrates a chemical transport model with a data-fusion approach to estimate 24-h average PM 2.5 and maximum daily 8-h averaged O 3 (MDA8-O 3) concentrations attributable to prescribed burns for the period 2013–2020. The Global Exposure Mortality Model and a log-linear exposure–response function were used to estimate the premature deaths ascribed to long-term prescribed burn PM 2.5 and MDA8-O 3 exposure in ten southeastern states. Our results indicate that prescribed burns contributed on annual average 0.59 ± 0.20 µg/m3 of PM 2.5 (∼10 % of ambient PM 2.5) over the ten southeastern states during the study period. On average around 15 % of the state-level ambient PM 2.5 concentrations were contributed by prescribed burns in Alabama (0.90 ± 0.15 µg/m3), Florida (0.65 ± 0.19 µg/m3), Georgia (0.91 ± 0.19 µg/m3), Mississippi (0.65 ± 0.10 µg/m3) and South Carolina (0.65 ± 0.09 µg/m3). In the extensive burning season (January–April), daily average contributions to ambient PM 2.5 increased up to 22 % in those states. A large part of Alabama and Georgia experiences ≥3.5 µg/m3 prescribed burn PM 2.5 over 30 days/year. Additionally, prescribed burns are responsible for an average increase of 0.32 ± 0.12 ppb of MDA8-O 3 (0.8 % of ambient MDA8-O 3) over the ten southeastern states. The combined effect of prescribed burn PM 2.5 exposure, population growth, and increase of baseline mortality over time resulted in a total of 20,416 (95 % confidence interval (CI): 16,562–24,174) excess non-accidental premature deaths in the ten southeastern states, with 25 % of these deaths in Georgia. Prescribed burn MDA8-O 3 was responsible for an additional 1,332 (95 % CI: 858–1,803) premature deaths in the ten southeastern states. These findings indicate significant impacts from prescribed burns, suggesting potential benefits of enhanced forest management strategies. [ABSTRACT FROM AUTHOR]