Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Unmasking risk variability in a changing climate: acute effects from exposure to outdoor heat and air pollution among patients with end-stage renal disease
    (2021) Remigio, Richard V; Sapkota, Amir; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    End-stage renal disease (ESRD) is a chronic condition that disproportionately affects communities of color and diabetics. Hallmark burdens include the lack of essential renal functions and routine life-saving dialysis treatments to filter and remove toxic wastes from the body. Given their compromised survival advantage, the ESRD population is vulnerable to adverse complications associated with acute environmental exposures. However, little is known about the effect of extreme heat events (EHE), air pollution, and ambient temperature on this targeted population. This dissertation focused on ESRD patients receiving hemodialysis treatments at Fresenius Medical Care facilities within the Northeastern United States region (n=60,717). Using longitudinal study design methods, we investigated the association between acute environmental exposures and the risk of all-cause mortality (ACM) and all-cause hospital admissions (ACHA).We applied case-crossover methods to estimate acute EHE effects on mortality and hospital admissions stratified by latitude, race/ethnicity, and comorbidities. Overall, risks varied, but same-day ACM and ACHA risks were most pronounced. ESRD patients with cardiovascular disease (rate ratio [RR], 2.14; 95% CI:1.91-2.40) and cerebrovascular disease (RR, 1.47; 95% CI:1.26-1.71) had notably increased risks of same-day EHE-related mortality. We furthered our investigation by studying PM2.5 and O3 effects using a similar study design but considered the role of EHE as a modifier and incorporated distributed lag nonlinear modeling to account for cumulative lag structures. Pooled same-day EHE-adjusted models estimated an 8% ACM rate increase when O3 concentrations exceeded air quality standards during warmer months. Our data suggest that EHE can act as a modifier between O3 and ACM. Though, no effect modification by EHE was observed for acute air pollutant exposures and ACHA. Lastly, this dissertation explored the mediating role of selected thermoregulatory responses to increased temperature on ACM or ACHA outcomes using traditional mediation analyses. Systolic blood pressure before dialysis treatment (preSBP) and interdialytic weight gain change (IDWG) were identified as significant pathways. However, we observed inconsistent mediation in the IDWG pathway for ACM (-6.26%) and ACHA (-2.67%). Concomitant physiological changes in preSBP and IDWG may have little intermediary effect in combined pathway models. Overall, this research provided additional lines of evidence for enhancing patient response protocols and early warning systems to improve healthcare delivery in an era of a changing climate specific to subpopulations living with ESRD.
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    INVESTIGATING THE ASSOCIATION OF PHTHALATE EXPOSURES AND ADVERSE REPRODUCTIVE HEALTH OUTCOMES IN A REPRESENTATIVE SAMPLE OF U.S. WOMEN
    (2017) Bibb, Katrina Alexandra; Alcala, Lesliam Q; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Phthalates are endocrine disrupting chemicals present in a large variety of consumer goods. There is supporting evidence from animal studies that exposure to phthalates affect the female reproductive system by disrupting the epigenome and folliculogenesis/oogenesis. Although women of reproductive age experience higher phthalate exposures versus males due to frequent use of cosmetics and personal care products (PCP), studies investigating reproductive health effects of these chemicals are scarce. In this study, a nationally representative sample was used to investigate the association between exposure to phthalates (primarily in PCPs and cosmetics) and subfertility in women aged 18-44. We observed significantly higher phthalate levels among minority women and positive associations between DBP exposure and subfertility in regressions when adjusted for important covariates This is the first study to use such a sample of women to study the effects of phthalates on subfertility. More epidemiological studies are needed to investigate phthalate levels among minorities.