Epidemiological Assessment of Harmful Environmentally Linked Factors and Their Relationships With Environmental Justice

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Authors

Hurbain, Patrick Richard-Zachary

Issue Date

2024

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Dissertation

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Cancer Risk , Environmental Justice , Equity , Pollution , Risk Assessment

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Abstract

Introduction: This dissertation evaluates the exposure to and disparities in measured environmental pollutants distributed across the United States (U.S.) through air, water, and dusts and soils within the framework of Environmental Justice (EJ). EJ is the equitable distribution of environmental hazards with respect to socioeconomic factors like income, race, and country of origin. Environmental pollution has been linked to various negative public health outcomes, including both acute injury and chronic disease. Health outcome burdens linked to environmental pollution have been demonstrated to have strong socioeconomic ties, and those who experience the bulk of the pollution, tend to be from a minority racial group and low-income status. While the scope and interest in EJ has grown in the past two decades, studies on environmental pollution and its relationship with the socioeconomics across the country tend to be localized to single cities, zip code tabulated areas, zip code tabulations within single census tracts, or single regions. Results of these studies tend to find minority and low-income areas experience high environmental pollution burden, but these studies do not often assess multiple media or present a comprehensive picture of the magnitude of injustice across the U.S. Because of the existing literature is still growing, and typical EJ studies are computationally intense and suffer data availability issues, it is difficult to ascertain how widespread environmental injustice is in the U.S., and whether conditions are improving, worsening, or remaining static. Here, I include a series of studies to analyze the environmental conditions across the U.S. with respect to the air, the water, the soil, and dust in the households, with respect to the socioeconomic makeup of the U.S. Methods: The overall methodological frameworks for the included studies are similar yet the details vary. Chapter two evaluates the disparity in exposure to estimated lifetime cancer risks with respect to race along the rural-urban continuum. I use five years of census tract level estimated cancer risks from the National Air Toxics Assessment and AirToxScreen datasets produced by the United States Environmental Protection Agency (EPA) alongside paired socioeconomic factors from the United States Census Bureau (USCB) using multivariable linear and spatial regression modeling techniques to demonstrate disparity in exposure to air toxics by demographic makeup along the rural-urban continuum within census tracts for the entire U.S over nearly a decade. Chapter three evaluates the disparity with respect to racial makeup across U.S. counties in measured sediment metal pollution using the Water Quality Portal (WQP). I use stratified generalized linear modeling to demonstrate the existence of disparity in exposure to harmful metals in sediment. In the fourth chapter I use air quality data including the Air Quality Index (AQI), air Toxic Release Inventories (TRI), and annual monitored hazardous air pollutants (HAP) and multivariable linear regression to control for important confounders and explore variation in pollution distribution by exposure first, then risk with the help of different assessment approaches. And finally, I present preliminary results of an ongoing cohort study among children aged six months to six years analyzing exposure to harmful environmental compounds in soil and dust, as well as the children's prevalent exposures to these compounds by urine and excrement measurements in chapter five. Results: Results of multivariable linear regressions demonstrated widespread EJ issues with increasing proportions of Black, Asian, and Hispanic individuals, but not for increasing proportions of mixed-race individuals with respect to estimated cancer risk from air toxics exposures. Some meaningful inequality in deposited lead to sediment was found in increasingly Black and Hispanic areas, but the magnitude and degree of certainty is variable by state, and increasing proportions of mixed-race individuals was observed to be increasingly protective. In ambient air quality, emitted air pollutants from industry, and their estimated health effects, some disparity for Black, Asian, and Hispanic individuals were found, however data limitations are likely masking the full disparity. While on average air pollution is decreasing through time, there is a strong relationship along the urban-rural continuum and spikes in industry related pollution were observed. In children, there is high variation in measured metal concentration with available sample by the child's race, however no meaningful environmental injustice was found in preliminary sampling. Discussion: Environmental injustice for increasing proportions of Black, Hispanic, and Asian communities across the U.S. was consistently found, however the magnitude of the results are mixed. Income and increasing proportions of mixed-race/Other individuals relative to White individuals were consistently found to be protective against estimated cancer risks and distribution of environmental pollution. The rural-urban continuum plays an important role in the magnitude of exposure and the disparity in demographic makeup with respect to the exposure. While it was observed that overall environmental conditions are improving across the U.S. in the last decade, disparity in exposure and the magnitude for some of the pollution distribution in some areas remains high. Coverage error likely plays an important role in evaluating the magnitude and significance of EJ in the U.S., yielding possible underestimates in the association between environmental pollution and socioeconomic status. In some cases, increasing proportions of minority populations produce negative associations with environmental pollution, which indicates disparity against resident White populations, which are often in poor or remote areas. Future research should prioritize analyzing areas where there are large gaps in data coverage like mountainous populations and the southern states, and policy-makers should pay keen attention to areas where high concentrations of air pollution, water pollution, and estimated risks are prevalent. Where extreme inequity exists, like parts of California or the deep south, policy-makers should prioritize these areas in all regulatory and remediation capacity first.

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