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Wildfires present an increasing threat to many parts of the United States due to climate change. This dissertation explores a range of challenges arising from this threat in economics and policy, identifying several areas that require attention in shaping the response to wildfires -- specifically, the role of sociopolitical pressure in fire suppression, population health impacts from wildfire smoke, and climate policy.The first chapter examines whether sociopolitical pressure, measured by the newspaper coverage of wildfires, affects the allocation of personnel and aerial resources during wildfire suppression. Using a rich dataset of wildfire events from the Incident Status Summary (ICS-209) reports between 1999 and 2014, the study identifies causal effects using (1) a comprehensive set of variables controlling for wildfire threat, (2) the exogenous variation in the publication of significant historical events occurring just before the discovery of the wildfires. The analysis reveals that increased newspaper coverage of wildfires leads to significantly higher personnel usage. The paper does not find a significant effect of newspaper coverage on aircraft usage.The second chapter investigates the impacts of wildfire smoke on population health. Wildfire smoke and its impacts are notoriously challenging to estimate since smoke can travel hundreds of miles away from its source. Using a nationwide satellite-derived dataset of wildfire smoke plumes and infant mortality data from U.S. death certificates, the study identifies a significant effect of wildfire smoke exposure on infant mortality at the county-month level between 2006 and 2017. The results suggest that wildfire smoke causes approximately 56 infant (0 to 1 month old) deaths in the U.S. annually.The third chapter studies the interaction between wildfires and carbon sequestration programs by examining California's U.S. Forest Projects program, a subdivision of the Compliance Offset Program. The analysis reveals that forests enrolled in the program have higher risks of severe wildfires than comparable forests that are not enrolled. The design of the program likely attracts projects with a higher chance of losing sequestered carbon to wildfires, indicating adverse selection based on wildfire risks. These findings underscore the importance of accurately addressing wildfire risks in carbon sequestration programs.

Wildfires and extreme heat events are inherently linked; shared climatic drivers are simultaneously worsening both hazardous events in California. Populations likely experience exposure to a combination of these hazards, i.e., compound hazards; yet there is little known about this public health threat. Studies indicate wildfire smoke and extreme heat, independently, elevate risks for morbidity and mortality. In addition, epidemiologic evidence gives reason to suspect compound wildfire smoke and extreme heat could exacerbate health outcomes and present a greater threat to public health.This dissertation aims to examine multiple facets of compound wildfire smoke and extreme heat in California. Chapter one assesses the distribution of compound wildfire smoke and extreme heat exposures in California from 2011-2020. The exposure assessment uses a clinically meaningful definition of exposure to estimate populations with disproportionate vulnerabilities. Chapter two then estimates the joint effects of exposure to wildfire smoke and extreme heat within a short-term exposure lag window. Chapters two and three both utilize a statewide payer’s database to examine all-natural cause, cardiovascular, cerebrovascular, renal, and respiratory morbidity impacts. In Chapter three, exposures are examined at different time periods to evaluate temporally compounding wildfire smoke and extreme heat in two ways; that is, effect modification of extreme heat-related morbidity by wildfire smoke exposure weeks to months prior, and vice versa. Methods include descriptive mapping and exposure assessment to identify disproportionately exposed populations. Joint effects and effect modification are estimated using time-stratified case crossover design with conditional logistic regression models. Each chapter investigates different periods of exposure and characterizes findings by individual or community level factors, such as race and ethnicity, income, education, and rural and urban classifications. These studies utilize secondary datasets from trusted agencies in environmental health monitoring and exposure assessment, including public health surveillance. Altogether, the findings from this dissertation work provide evidence on the public health impacts of compound wildfire smoke and extreme heat. Exposures to compound wildfire smoke and extreme heat are increasing and their health impacts are synergistic, even for exposures across different periods of time. Individuals across California have been impacted by compound wildfire smoke and extreme heat in recent years; however, exposures were consistently highest within the Central Valley. In addition, health impacts were disproportionate, often by race and ethnic groups. This work improves characterization of vulnerable populations to help target joint mitigation of compound hazard risks.

This dissertation explores the economic consequences of wildfire and smoke in the United States. The third chapter, Wildfire smoke in the United States, is joint work with Matthew Wibbenmeyer, and examines regional and temporal trends in wildfire smoke impacts. It synthesizes research on health, economic, and behavioral impacts, proposing modifications to federal air quality regulations to address wildfire smoke. The second chapter, Wildfire, smoke, and outdoor recreation in the western United States, is a collaboration with Margaret Walls and Matthew Wibbenmeyer. It focuses on the effects of wildfire and smoke for outdoor recreation. The paper combines millions of administrative campground reservation records with daily satellite data on wildfire, smoke, and air pollution, finding that more than ten percent of available recreation days are affected by severe smoke in some regions. The first chapter, Non-market damages of wildfire smoke: evidence from administrative recreation data, is also a collaboration with Margaret Walls and Matthew Wibbenmeyer. This chapter exploits the dataset of the second chapter to provide among the first revealed preference estimates of smoke damages. A structural model of sequential recreation decisions finds that smoke reduces welfare by $107 per person per trip. Annually, more than 21.5 million outdoor visits in the western United States are affected by wildfire smoke, with welfare losses of $2.3 billion. These findings contribute to a growing body of evidence on the costs of wildfire smoke.

The results of two previously published reports of the events and impacts of the Campfire wildfire smoke exposure that occurred in California in 2018 are amplified from the point of view of the potential toxic mechanism involved. The Campfire wildfire led to the exposure of a breeding colony of macaque monkeys (Macaca mulatta) during the peak of their breeding season in 2018–2019. Considering the timing, adverse effects, and endocrine implications reported, the cumulative evidence points to an early toxic sensitive period that can lead to birth defects in higher primates and human pregnancies. This deeper inspection of the published observations provides important caveats and useful guidance for future investigators. The unique higher primate placental–adrenal–brain axis may limit the use of many traditional toxicologic approaches. Retrospective neurological evaluations of human fetuses exposed to air pollutants during organogenesis and subsequent retrospective characterization of air samples using in vitro and animal models may be the best procedures to follow.

Introduction Wildfire smoke (WFS) exposure is a growing threat to human health, and lower socioeconomic position (SEP) has been shown to increase pollution susceptibility. Studies of SEP-related susceptibility, however, are often compromised due to spatial confounding between lower-SEP and pollution. Here we examine outdoor-housed nonhuman primates, living in natural social hierarchy in a common location, born during years of high vs. low WFS, to examine the separate and combined effects of WFS and social rank, an analog to SEP, on lung and immune function. Methods Twenty-one females were born during extreme WFS events in summer 2008; 22 were born in summer 2009, during low WFS. Pulmonary function and circulating cytokines were measured three years later, in adolescence. We estimated fine particulate (PM2.5) and ozone exposures during each animal's first 90 days and three years of age using regulatory data. Early-life social status was estimated using maternal rank at birth, as rank in females is relatively stable throughout life, and closely approximates mother's rank. We tested associations among WFS exposure, rank, and endpoints using linear regression and ANOVA. Results Higher WFS exposure in infancy was, on average, associated with lower functional residual capacity (FRC), residual volume (RV), tissue compliance (Ct), and IL-8 secretion in adolescence. Higher social rank conferred significantly higher expiratory reserve volume (ERV) and functional residual capacity (FRC) solely among those born in the high-WFS year (2008). Differences in effects of rank between years were not significant after adjustment for multiple comparisons. Conclusions Exposure to WFS in infancy generally conferred lower adolescent respiratory volumes and inflammatory cytokines. Higher rank conferred higher respiratory volumes only among females born during WFS, suggesting the possibility that the health benefits of rank may be more apparent under environmental challenge., Wildfire smoke; Infancy exposure; Socioeconomic status; Lung volume; Cytokine response.

Wildfire smoke is an increasing environmental health threat to which children are particularly vulnerable, for both physiologic and behavioral reasons. To address the need for improved public health messaging this review summarizes current knowledge and knowledge gaps in the health effects of wildfire smoke in children, as well as tools for public health response aimed at children, including consideration of low-cost sensor data, respirators, and exposures in school environments. There is an established literature of health effects in children from components of ambient air pollution, which are also present in wildfire smoke, and an emerging literature on the effects of wildfire smoke, particularly for respiratory outcomes. Low-cost particulate sensors demonstrate the spatial variability of pollution, including wildfire smoke, where children live and play. Surgical masks and respirators can provide limited protection for children during wildfire events, with expected decreases of roughly 20% and 80%for surgical masks and N95 respirators, respectively. Schools should improve filtration to reduce exposure of our nation's children to smoke during wildfire events. The evidence base described may help clinical and public health authorities provide accurate information to families to improve their decision making.