Maryland Institute for Applied Environmental Health Theses and Dissertations

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    (2022) Chattopadhyay, Suhana; Sapkota, Amy R; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    To evaluate the adverse health effects associated with tobacco smoking, the majority of studies have largely focused on the impact of chemical constituents in tobacco products and less on the impact of microbial contaminants within these products. Similarly, the United States (U.S.) Food and Drug Administration’s (FDA) Family Smoking Prevention and Tobacco Control Act (FSPTCA) requires tobacco manufacturers and importers to test and report on chemical constituents included on their list of harmful and potentially harmful constituents (HPHCs) in tobacco products and tobacco smoke; however, this HPHC list excludes microorganisms. Nevertheless, over the past decade, an increasing number of studies have explored the bacterial microbiome of tobacco products (e.g., cigarettes, little cigars, cigarillos, hookah and smokeless tobacco) and mainstream smoke. These studies have yielded robust data on bacterial diversity and bacterial community composition within individual tobacco product types. However, to date, there are no comparative characterizations of the bacterial microbiome across diverse tobacco products. In particular, there have been no studies that have characterized the metabolically-active (live) bacterial communities across these products; bacterial communities that might be transferred to the user’s oral cavity and cause subsequent adverse health effects. Furthermore, from an oral health perspective, while smoking/using tobacco products causes significant oral dysbiosis (bacterial community disturbances), there is a lack of data on the potential transfer of bacteria from tobacco products to user’s oral cavities or transient temporal changes in the oral microbiome that might result from smoking these tobacco products. Moreover, there are limited data comparing oral microbiome differences between cigarette smokers and smokeless tobacco users. To address these knowledge gaps, my dissertation research involved a comparative analysis of the bacterial microbiome of commercially-available tobacco products and anevaluation of the impacts of tobacco use on the oral microbiome of users. My specific aims were: 1) To evaluate the compositional differences in the bacterial microbiome between conventional tobacco products; 2) To evaluate transient changes in the oral microbiome of cigarette smokers after a single use of a little cigar; and 3) To conduct a comparative characterization of the oral microbiome between cigarette users, smokeless tobacco users, and non-users over time. Overall, I found that each type of conventional tobacco product harbored a significantly different bacterial community, with mentholation and/or flavoring being a significant driver of bacterial community changes. However, across all products the majority of the metabolically-active bacterial community was identified as Pseudomonas, along with members of the phylum Firmicutes, as well as a few pathogenic species previously associated with animal/human respiratory diseases. In analyzing the oral microbiome of cigarette smokers, I found that a singleuse of a little cigar product did not cause transient changes in the oral microbiome. In analyzing longer temporal effects of smoking on the oral microbiome, I found that, even though total bacterial diversity and composition did not change over time, multiple bacterial taxa were significantly different, with regard to their relative abundance, after four months. In addition, I found that dysbiosis of the oral microbiome was dependent on the type of tobacco product used (cigarettes or smokeless tobacco), and that tobacco smokers/users’ oral microbiomes harbored a more diverse set of bacterial species when compared to that of non-users. In summary, this work provides a comparative analysis of the total and metabolically-active bacterial microbiome of tobacco products, as well as rich findings regarding the relationship between tobacco use and oral microbiome dysbiosis. These data address major research priorities of the FDA relating to furthering our understanding of the adverse health risksassociated with tobacco smoking. Specifically, my data will add to the current body of knowledge regarding the potential role of tobacco bacterial communities in the development of smoking-related diseases. My data also can be leveraged by tobacco regulatory bodies to make future evidence-based policy changes that help reduce risks associated with microorganisms in tobacco products and protect public health.
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    (2022) Mansfield, Tavis; Turner, Paul; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In Ethiopia, the potential to be infected with malaria may increase this decade due to the expected increases in available breeding habitats created by the filling of the Grand Ethiopian Renaissance Dam (GERD) and its reservoir as well as internal displacement and forced migration of tens of thousands of people due to the flooding of local communities by the filling of the GERD’s reservoir and ongoing civil conflict in the Tigray Region of northern Ethiopia. A One Health framework was used in this research along with refugee migration and resettlement information and, risk evaluation tools to assess the potential health effects of the construction and filling of the GERD and its reservoir in Western Ethiopia on the burden of malaria and the human population living in the same area. This thesis shows Anopheles mosquitoes that are the primary vector of malaria are present in Western Ethiopia and present an entomological surveillance tool that can be implemented in the region. The author also considers the human population movement and illustrate the current vulnerabilities of the various groups involved.
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    (2022) Ezeugoh, Rosemary Ifeoma; Payne-Sturges, Devon; Puett, Robin; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    BackgroundExisting research has investigated the relationships between sociodemographic characteristics and air toxic exposure in the United States. However, a few studies have examined the neurological risk from exposure to air toxics. The purpose of the study was to determine the correlation between sociodemographic variables and neurological risk due to exposure to air toxics. Also, spatial meth-ods were used to understand the distribution of neurological risk and sociodemographic character-istics. Methods Air toxic neurological risk data were obtained from the United States Environmental Protection Agency's National-scale Air Toxics Assessment and sociodemographic data from the 2010-2014 American Community Survey US Census Bureau. The NATA dataset contains 24 neurotoxic air pollutants. The hazard quotient (HQ) for each air pollutant was quantified by calculating the ratio of the inhalation exposure concentration (EC) to the reference concentration (RfC). In addition, the EPA additively models the neurological risks of different pollutants (HQ) to estimate an aggregate neurological risk score (hazard index (HI)) for each census tract. We conducted statistical analysis using R and spatial analysis using ArcGIS 10. Results The mean cumulative neurological risk (HI) from all sources was 0.05, and all HI<1 for all tracts in Minnesota. The range of values for HI is 1 to >1, with >1 being the greatest harm. Percent pov-erty, percent without high school education and percent non-Hispanic white were weakly negative-ly correlated with cumulative neurological risk. In comparison, median household income, percent unemployed, percent non-Hispanic black, percent Hispanic and percent people of color were weak-ly positively correlated with cumulative neurological risk. The choropleth map of cumulative neuro-logical risk showed that individuals in Minneapolis-St. Paul may be disproportionately exposed to air toxics. Conclusions These findings suggest that there may be an unequal distribution of neurotoxic air pollutants, espe-cially in Minneapolis-St. Paul. Study results may inform and target public health efforts at specific locations to eliminate sociodemographic inequalities in exposure to neurotoxic air pollutants.
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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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    (2019) Malayil, Leena; Sapkota, Amy R; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Bacteria are ubiquitous in irrigation water resources and can include pathogens that may compromise food safety and public health. However, only a small fraction of total bacterial community members in water can be identified through standard culture-based laboratory methods. 16S rRNA and shotgun sequencing techniques have improved the identification of non-culturable bacteria in water resources. Nevertheless, because sequencing approaches are nucleic-acid based, they are unable to differentiate between the proportion of bacterial communities identified that are live and metabolically-active versus those that are represented by free, relic DNA, not present in viable cells. To bridge this knowledge gap, my dissertation research coupled DNA-labeling (using 5-bromo-2’- deoxyuridine (BrdU) and propidium monazide (PMA)) with next-generation sequencing approaches to identify and comprehensively characterize metabolically-active bacteria in multiple nontraditional irrigation water sources in the Mid-Atlantic region. My aims were as follows: 1) To characterize the metabolically-active fraction of bacterial communities, as well as antibiotic resistance genes and virulence gene profiles in nontraditional irrigation water sources; 2) To evaluate culture-dependent and -independent methods in the detection of metabolically-active pathogenic and non-pathogenic Vibrio species in four nontraditional irrigational water sources; and 3) To track metabolically-active bacterial communities from rooftop-harvested rainwater to irrigated produce in Maryland. Overall, we identified diverse metabolically-active bacterial communities in all nontraditional water sources. Notably, we observed the presence of viable bacteria of importance to both human and/or animal health (Actinobacterium spp., Flavobacterium spp., Aeromonas spp. Pseudomonas spp. and Vibrio spp.). Interestingly, diverse antimicrobial resistance and virulence genes were predominantly found in non-BrdU-treated samples, indicating that these genes can persist in relic DNA and could be transferred to other environmental bacteria through transformation events. We also source-tracked viable bacteria, including Sphingomonas spp., Enterobacter spp., Enterococcus spp, and Citrobacter spp. from rooftop-harvested irrigation water to produce. In summary, this work provides the first description of total, viable, and metabolically-active bacterial communities in different nontraditional irrigation water sources. These data can be used to improve risk characterization of these water sources, and ultimately inform the selection of appropriate cost-effective remediation methods to treat these waters prior to irrigation activities in order to prevent foodborne outbreaks.