Research

There is substantial academic, regulatory, and public attention on per- and polyfluoroalkyl substances (PFAS), often dubbed ``forever chemicals'' due to their resistance to degradation. PFAS are used in a wide variety of production processes and consumer products, are found in food and drinking water sources, and are subsequently ubiquitously present in samples of human blood, breast milk, and environmental media collected in the United States and globally. Exposure to PFAS has been linked to a litany of health effects including kidney and testicular cancer, immune system hypersensitivity and suppression, endocrine disruption, and adverse reproductive outcomes such as decreased fertility and lower birth weights. However, certain health endpoints are understudied in human populations and many questions remain unanswered, with notable gaps in the literature regarding exposure pathways, health burdens, replacement PFAS, and disparate impacts. Regulation of PFAS is just beginning for many environmental media, and research opportunities described in this paper can potentially inform the development of new policies to address the PFAS problem.

We use administrative panel data from seven states covering nearly 3 million students to document and explore variation in “academic mobility,” a term we use to describe the extent to which students’ ranks in the distribution of academic performance change during their public schooling careers. We find that student ranks are highly persistent during elementary and secondary education—that is, academic mobility is limited in U.S. schools on the whole. Still, there is non-negligible variation in the degree of upward mobility across some student subgroups as well as individual school districts. On average, districts that exhibit the greatest upward academic mobility serve more socioeconomically advantaged populations and have higher value-added to student achievement.

We examine the relationship between contemporaneous fine particulate matter exposure and COVID-19 morbidity and mortality using an instrumental variable approach. Harnessing daily changes in county-level wind direction, we show that arguably exogenous fluctuations in local air quality impact the incidence of confirmed COVID-19 cases and deaths. We find that a one &#956g/m&#179 increase in PM 2.5, or 15% of the average PM 2.5 concentration in a county, increases the number of same-day confirmed cases by 1.8% from the mean case incidence in a county. A one &#956g/m&#179 increase in PM 2.5 increases the same-day death rate by just over 4% from the mean. These effects tend to increase in magnitude over longer time horizons and are robust to a host of sensitivity tests. When analyzing potential mechanisms, we also demonstrate that an additional unit of PM 2.5 increases COVID-19-related hospitalizations by 0.8% and use of intensive care units by 0.5% on the same day. Using individual case records, we also show that higher PM 2.5 exposure at the time of case confirmation increases risk of later mechanical ventilation and mortality. These results suggest that air pollution plays an important role in mediating the severity of respiratory syndromes such as COVID-19.

Diesel emissions from school buses expose children to high levels of air pollution; retrofitting bus engines can substantially reduce this exposure. Using variation from 2,656 retrofits across Georgia, we estimate effects of emissions reductions on district-level health and academic achievement. We demonstrate positive effects on respiratory health, measured by a statewide test of aerobic capacity. Placebo tests on body mass index show no impact. We also find that retrofitting districts experience significant test score gains in English and smaller gains in math. Our results suggest that engine retrofits can have meaningful and cost-effective impacts on health and cognitive functioning.

Service area boundaries are the geographic delineation of a drinking water system's customer base. A lack of precise service area boundaries may introduce errors in how measures of water quality are geospatially assigned in academic or regulatory work, potentially hindering our ability to locate and accurately characterize environmental justice concerns in drinking water. Many advances have been made in the collection and modelling of service areas, but there has been minimal systematic testing of the implications of employing distinct service area boundary types in the published literature. While it is generally understood that more accurate service area assignment methods will improve the precision of environmental justice analyses of drinking water quality, it is unclear how various assignment methods would impact the conclusions of empirical analyses or the potential magnitude of bias. This paper aims to fill this gap by summarizing a set of relatively novel environmental justice indicators in drinking water across all known service area assignment methods. We explore drinking water quality measures for arsenic, bacterial detection, disinfection byproduct formation, lead, nitrates, PFAS, and health-based violations of the Safe Drinking Water Act. We summarize each drinking water quality metric across service area assignment methods including the use of county served, zip codes served, the EPIC/SimpleLab dataset, boundaries created by the U.S. Geologic Survey, and a national data layer produced by EPA's Office of Research and Development. We find disparities in drinking water quality with respect to every drinking water quality metric included in this analysis, and we find that conclusions regarding the presence of a disparity depend on the service area boundary selected for at least one group of environmental justice concern for each drinking water quality measure. This paper helps to motivate the importance of collecting service areas and producing as well as maintaining a high-quality nationally consistent geodatabase of drinking water system service areas.

Coal ash accounts for one third of industrial water pollution in the United States. I assess the relationship between coal ash surface water discharges and three relevant outcomes: surface water quality, municipal system water quality, and fetal health indicators from a birth certificate database in North Carolina. Identification relies on geographic variation in downstream status of monitoring sites and municipal water intake locations, plant closures or conversions, and the relative quantity of coal ash released over time. I find that coal ash releases are associated with higher conductivity and pH in both downstream surface waters and municipal water supplies sourced from these waters. Water systems affected by coal ash tend to have more Safe Drinking Water Act violations for disinfectant byproducts, inorganic chemicals, and health-based violations. I quantify the costs of coal ash water pollution with respect to fetal health and home sales. Exploiting variation arising from mothers' moves, I find that a newborn potentially exposed to coal ash water pollution is 1.7 percentage points more likely to have low birthweight compared to an unexposed sibling. I conclude by estimating how a legislative act mandating drinking well testing affected home sale prices in regions around coal ash plants. After the act, sale prices of homes within 1 mile of coal ash ponds declined by 12-14%, or over $37,000.

Prior work shows that air pollution affects cognitive performance. School bus diesel emissions meaningfully contribute to this exposure for school-age children. I exploit variation in the timing and location of 17,901 school bus diesel engine retrofits or replacements across the US from 2008 to 2016 to test how these bus fleet investments affect air quality and student test scores. I use satellite-based fine particulate matter (PM 2.5) measurements from the Atmospheric Composition Analysis Group to provide the first evidence that these engine retrofits significantly improve surface-level ambient air quality, suggesting potentially large spillover benefits. Retrofitting school buses is also associated with a 0.05-0.06 standard deviation increase in standardized test scores. Moreover, each additional microgram of fine particulate matter per cubic meter is associated with a precisely-estimated decrease in English and math test scores of 0.0056 standard deviations. Finally, I calculate the benefit of these test score and air quality improvements, finding that $170 million spent in grants by the EPA led to approximately $4.75 billion in external benefits. Whether considered from a mortality and clinic cost or test score perspective, the retrofits pass a benefit-cost test.

An increasing emphasis on principals as key to school improvement has contributed to efforts to elevate principal effectiveness that have taken various forms across the US. The primacy of the state as the focal point of educational reform elevates the value of understanding commonalities and differences among states in characteristics of principals, the distribution of principals among schools and ultimately the policies associated with more effective school leadership, particularly for disadvantaged children. This paper describes major state policies, the distribution of elementary school principals among schools along a several dimensions, and pathways to the principalship to illustrate similarities and differences among six states in the tenure and experience distributions and how these vary by student demographic characteristics and district size. Measurement of principal effectiveness and its relationship with principal characteristics and state policies would be ideal, but complications introduced by the dynamics of principal influences and confounding effects of other factors inhibit this effort. Nonetheless, school value added to achievement provides information on differences in principal effectiveness, and we report within-school variation value added across principal regimes and the associations between value added and principal characteristics. The analysis reveals many similarities and some differences among the states, some of which are related to differences in governance structures. Perhaps the most striking differences relate to the pathways to the principalship including the fraction of principals with experiences as assistant principals and teachers.

An increasing emphasis on principals as key to school improvement has contributed to efforts to elevate principal effectiveness that have taken various forms across the US. The primacy of the state as the focal point of educational reform elevates the value of understanding commonalities and differences among states in characteristics of principals, the distribution of principals among schools and ultimately the policies associated with more effective school leadership, particularly for disadvantaged children. This paper describes major state policies, the distribution of elementary school principals among schools along a several dimensions, and pathways to the principalship to illustrate similarities and differences among six states in the tenure and experience distributions and how these vary by student demographic characteristics and district size. Measurement of principal effectiveness and its relationship with principal characteristics and state policies would be ideal, but complications introduced by the dynamics of principal influences and confounding effects of other factors inhibit this effort. Nonetheless, school value added to achievement provides information on differences in principal effectiveness, and we report within-school variation value added across principal regimes and the associations between value added and principal characteristics. The analysis reveals many similarities and some differences among the states, some of which are related to differences in governance structures. Perhaps the most striking differences relate to the pathways to the principalship including the fraction of principals with experiences as assistant principals and teachers.