Theses and Dissertations from UMD
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Item THE PRICE OF FRESH AIR: ESSAYS ON THE INTERACTIVE EFFECTS OF TECHNOLOGY AND AIR POLLUTION ON ECONOMIC ACTIVITY(2022) Jeong, Jaehoon; Gopal, Anandasivam; Business and Management: Decision & Information Technologies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With recent dramatic industrialization around the world, air quality has become a global issue. In my dissertation, I investigate the effects of air pollution on the omni-channel retail business and public transportation.In the first essay, I study how diminished air quality affects the substitutive relationship between offline and online sales associated with a cosmetics retailer located in South Korea. I specifically test how air pollution may affect the actual demand that occurs during these promotion days across the offline and online channels. Interestingly, polluted air boosts online sales and online promotion effectiveness. Unexpectedly, air pollution is unlikely to hurt offline sales, and even increase offline sales and offline promotion effectiveness. I also find a notion of the inverted-U shaped reaction to the seriousness of polluted air consistently in offline sales. The second essay examines the effect of mobile nudges on behavioral changes focusing on public transportation ridership. I study the effect of air quality categories with easy-to-interpret user interface and air quality notification using a regression discontinuity design. I show that mobile nudges effectively help users make better decisions to protect themselves. My additional analyses suggest that the effect of mobile nudges may vary by schedule flexibility and travel purposes. I also observe adaptation behavior to air pollution over the years. In my third essay, I study the interaction between air pollution, channels, and product categories in the online retail context. Combined with environmental changes, differences in product characteristics and channel fit can create varied patterns of demand shift. Considering air pollution-driven shopping motivation, I examine how air pollution affects relative product category sales across mobile and PC channels. My results show that air pollution can increase mobile sales volume more than PC sales volume in urban areas. Also, air pollution creates a larger effect on skin care products and lower priced items than on makeup products and higher priced items accordingly. Overall, my dissertation suggests theoretical and practical implications for the business and social impacts of air pollution, which should aid decision-makers in formulating business and sound policy.Item The Benefits of Metro Rail in Mumbai, India: Reduced Form and Structural Approaches(2022) Suri, Palak; Cropper, Maureen L; Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation studies the welfare effects of introducing metro rail in the city of Mumbai, India using a combination of reduced form and structural econometric approaches. Mumbai is one of the most densely populated cities in the world. To supplement its extensive, but overcrowded, network of Suburban Railway, over 300 km of metro rail lines are planned. Each chapter in this dissertation looks at a different dimension of the benefits of metro rail in the city and is a standalone paper. In Chapter 1, I analyze the benefits of the introduction of metro rail in Mumbai by computing the value of travel time savings to households. I estimate preferences for commute time from residence to work using two discrete choice models: a commute mode choice model assuming fixed residence and work locations for short-term analysis, and a combined housing and commute mode choice model assuming fixed work location for medium-term analysis. Using the expected compensating variation measure, I value travel time savings due to: (i) Line 1 (11.4 km), operational since 2014, and (ii) three upcoming lines (92 km). The value of short-term benefits for an average beneficiary under either project is Rs. 71-99 per month (9-14% of the average out-of-pocket cost). The medium-term benefits are an order of magnitude higher than the short-term benefits due to the possibility of household re-sorting. Women, college educated workers, and high-income households receive greater benefits. Benefits of the upcoming network accrue to more individuals and are more dispersed, both spatially and demographically, than the benefits of Line 1. A limitation of the partial equilibrium models in this chapter is that they capture benefits only to households and only through the channel of time savings. In Chapter 2, I address this by studying the net benefits of Metro Line 1. In Chapter 2 (co-authored with Maureen Cropper), we study the impact of Metro Line 1 in Mumbai on property prices using difference-in-differences in an event study framework. We use administrative data on assessed land values from 2011-18 for 726 sub-zones in the city. Comparing areas within 1 km of the metro with those beyond 1 km but within 3 km, we estimate the effects on property values for commercial, industrial, and residential properties. We find a significant and persistent increase in prices for all land use categories in the treated areas relative to the control areas after Metro Line 1. The price increase ranges from 13% for commercial properties to 17% for residential. We show that improvements in employment accessibility and other location amenities are plausible mechanisms underlying these effects. In Chapter 3 (co-authored with Maureen Cropper), we study the effects of the introduction of Metro Line 1 in Mumbai on air pollution. We use data on daily average levels of nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter (PM10) from ground monitoring stations in an event study framework to identify the changes in pollution levels following the opening of Metro Line 1. We find a robust and significant reduction in the level of NO2 and no evidence of changes in PM10 and SO2. We also find a decline in the level of Aerosol Optical Depth measured using satellite data at 1 km resolution.Item 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.Item EXAMINATION OF PHOTOCHEMISTRY AND METEOROLOGY OF ATMOSPHERIC POLLUTANTS FROM THE NORTH CHINA PLAIN(2020) Benish, Sarah Elizabeth; Dickerson, Russell R; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasingly severe air pollution over metropolitan regions in China has raised attention in light of its local and regional impacts on health and climate. Computer models can simulate complex interactions between photochemistry and meteorology to inform policy decisions in reducing ground-level pollution. However, models rely on an accurate portrayal of emissions that often possess large uncertainties over regions with evolving pollution characteristics. This work is comprised of a quantitative analysis of air pollutants in the North China Plain that strives to improve such uncertainties by identification of important sources and meteorological conditions for pollution through the combination of observations and models. Measurements used in this dissertation focus on in situ observations from the Spring 2016 Air chemistry Research in Asia (ARIAs) campaign, which sampled atmospheric composition across the heavily populated and industrialized Hebei Province in the North China Plain. High amounts of ozone (O3) precursors were found throughout and even above the planetary boundary layer, continuing to generate O3 at high rates to be potentially transported downwind. Evidence for the importance of anthropogenic VOCs on O3 production is presented. Concentrations of NOx and VOCs even in the rural areas of this highly industrialized province promote widespread O3 production and in order to improve air quality over Hebei, both NOx and VOCs should be regulated. The ARIAs airborne measurements also provide a critical opportunity to characterize chlorofluorocarbons (CFCs) over a suspected CFC-11 source region in China, finding mixing ratios were well above 2016 global background levels. Based on correlations of CFCs with compounds used in their manufacture, I identify likely source regions of new CFCs production and release, in violation of the Montreal Protocol. Finally, I examine the influence of meteorology on surface and aloft measurements during ARIAs. A multiday persistent high pressure episode is presented as a case study to examine the influence of regional transport on air quality measured during ARIAs. This dissertation provides valuable information for understanding one of the most polluted regions in China. Coordinated field and modeling efforts can together provide scientific guidance to inform pollution control measures to meet air quality targets in China.Item Relationships of social and physical environmental factors with cardiometabolic outcomes(2019) Huang, Dina; Puett, Robin; Nguyen, Quynh C; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The social and physical environmental factors impact health in general and have been linked with increased risks of cardiometabolic outcomes including obesity, diabetes, hypertension and cardiometabolic biomarkers. The dissertation added to important knowledge on this topic in two ways: 1) by leveraging innovative Twitter-derived characteristics to study the potential influence of social environment on cardiometabolic outcomes, 2) investigating the effects of air pollution exposures on cardiometabolic outcomes in youth living with type I diabetes. The first study investigated the associations between Twitter-derived area-level predictors (happiness, diet, physical activity) with cardiometabolic outcomes (obesity, diabetes, hypertension) using a nationally representative sample from National Health and Nutrition Examination Survey (NHANES). People living in neighborhoods with higher happiness, healthier diet and more physical activity had lower prevalence of obesity and hypertension but not diabetes. Twitter-derived social neighborhood characteristics can be used to identify communities with higher risk of cardiometabolic outcomes. We obtained data from SEARCH for Diabetes in Youth (SEARCH) study for the second and the third study. The second study examined the associations between chronic exposure to air pollution and glucose hemostasis (HbA1c) in youth living with type I diabetes. Particulate matter with aerodynamic diameter <2.5 (PM2.5), proximity to heavily trafficked roads and annual average daily traffic count were associated with higher HbA1c in study site South Carolina, Colorado and Washington, but not in study site Ohio and California. Differences in particulate matter compositions may explain the inconsistent results. The third study assessed the effect of acute exposure to air pollution on subclinical CVD markers including pulse wave velocity (PWV), augmentation index (AIx) and brachial distensibility (BrachD) using a repeated measures design. Reduction in PM2.5 on the day prior to assessment was associated with lower AIx, but not associated with either PWV or BrachD. In summary, exposure to air pollution may be associated with cardiometabolic outcomes and reducing air pollution may have implications in early prevention of cardiovascular complications for youth living with type I diabetes. Overall, reducing social stressors and reducing hazardous physical environmental factors may decrease the risk of cardiometabolic outcomes, providing possible directions for CVD prevention for public health practitioners.Item Prediction Of Air Pollutant From Poultry Houses By A Modified Gaussian Plume Model(2017) Yang, Zijiang; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Concentrated animal feeding operations release a variety of potential pollutants, such as ammonia and particulate matters (PM). Field measurements are time consuming, costly, and only provide a limited amount of spatial and temporal information. Air dispersion models can serve as an alternative solution, especially if coupled with field sampling. The Gaussian plume model (GPM) is a mathematical model that assumes steady state condition. Previous studies have used the GPM to evaluate and analyze source. However, much less is known about utilizing GPM to simulate plumes from horizontal sources, such as the exhaust fans from poultry houses. The purpose of this study is to modify and validate a GPM to predict air pollutant emissions from the poultry houses. Two major assumptions were applied on the model, 1) a virtual releasing point was proposed behind the ventilation fan, and 2) ventilation fan was considered as the dominant wind direction in the model for short distance (< 50 m). The modified model was validated with field experimental data. Performance and sensitivity of the model were also evaluated. Fraction of predictions within a factor of two of observations (FAC2) of NH3 and PM were 0.609 and 0.625. Model-predicted concentrations of NH3 were 1.5 times of the measured values on average. Model-predicted concentrations of PM was 0.98 times of the observed values on average.Item ASSOCIATIONS BETWEEN AMBIENT PARTICULATE MATTER EXPOSURES, STROKE, AND MARKERS OF CARDIOVASCULAR INFLAMMATION(2017) Fisher, Jared A.; Puett, Robin C; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stroke is a leading cause of morbidity and mortality in the United States with 795,000 people experiencing a new or recurrent stroke every year. Identifying modifiable risk factors for stroke should therefore be considered a research priority. While associations between ambient exposure to air pollution and other cardiovascular diseases are well established in the literature, the evidence linking particulate matter (PM) air pollution exposures to the risk of ischemic or hemorrhagic stroke remains equivocal. Furthermore, the exact pathophysiologic mechanisms by which exposure to PM may lead to cerebrovascular events are not yet fully understood. Hypothesized pathways include the mediation of effects through a combination of inflammatory responses, autonomic dysregulation, and/or vascular endothelial disturbances. This dissertation addresses existing gaps in the literature in three separate studies. Two time-stratified case-crossover studies examined the association between short-term PM exposures and stroke risk, one in the Health Professionals Follow-up Study (HPFS) and the other among a large database of Maryland stroke hospitalizations. Conditional logistic regression models were used to examine associations by stroke subtype, population subgroups, and clinically-relevant variables. Our third study took place within the Nurses’ Health Study cohort. Multivariable linear regression models were used to examine the associations between PM and residential distance to road exposures and four inflammatory biomarkers (CRP, IL-6, fibrinogen, and ICAM-1). We found positive significant associations between PM10 and ischemic stroke events in the HPFS cohort, and associations were elevated for nonsmokers, aspirin nonusers, and those without a history of high cholesterol. Concentrations were elevated for both CRP and IL-6 among participants who lived close to a major roadway, but no significant results were found by estimated PM exposure. This work provides additional evidence that PM exposure is associated with ischemic stroke and adds to the current literature that those not currently taking aspirin and those without a history of high cholesterol may be at elevated risk. Although the direct role of inflammatory processes requires more investigation, this work does provide additional evidence that proximity to traffic may influence cardiovascular-related inflammation.Item Development, enhancement, and evaluation of aircraft measurement techniques for criteria pollutants(2014) Brent, Lacey Cluff; Dickerson, Russell R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The atmospheric contaminants most harmful to human health are designated Criteria Pollutants. To help Maryland attain the national ambient air quality standards (NAAQS) for Criteria Pollutants, and to improve our fundamental understanding of atmospheric chemistry, I conducted aircraft measurements in the Regional Atmospheric Measurement Modeling Prediction Program (RAMMPP). These data are used to evaluate model simulations and satellite observations. I developed techniques for improving airborne observation of two NAAQS pollutants, particulate matter (PM) and nitrogen dioxide (NO2). While structure and composition of organic aerosol are important for understanding PM formation, the molecular speciation of organic ambient aerosol remains largely unknown. The spatial distribution of reactive nitrogen is likewise poorly constrained. To examine water-soluble organic aerosol (WSOA) during an air pollution episode, I designed and implemented a shrouded aerosol inlet system to collect PM onto quartz fiber filters from a Cessna 402 research aircraft. Inlet evaluation conducted during a side-by-side flight with the NASA P3 demonstrated agreement to within 30%. An ion chromatographic mass spectrometric method developed using the NIST Standard Reference Material (SRM) 1649b Urban Dust, as a surrogate material resulted in acidic class separation and resolution of at least 34 organic acids; detection limits approach pg/g concentrations. Analysis of aircraft filter samples resulted in detection of 8 inorganic species and 16 organic acids of which 12 were quantified. Aged, re-circulated metropolitan air showed a greater number of dicarboxylic acids compared to air recently transported from the west. While the NAAQS for NO2 is rarely exceeded, it is a precursor molecule for ozone, America's most recalcitrant pollutant. Using cavity ringdown spectroscopy employing a light emitting diode (LED), I measured vertical profiles of NO¬2 (surface to 2.5 km) west (upwind) of the Baltimore/Washington, area in the morning, and east (downwind) in the afternoon. Column contents (altitude integrals of concentration) were remarkably similar (≈3x1015 molecules cm−2). These measurements indicate that NO2 is widely distributed over the eastern US and help quantify the regional nature of smog events and prove extensive interstate transport of pollutants. These results were used to help shape air pollution control policy based on solid science.Item Short-term effects of ambient ozone on stroke risk in South Carolina(2013) Montresor-Lopez, Jessica Anne; Puett, Robin C; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent reports have suggested that exposure to ozone is associated with stroke events; however, findings have been inconsistent. Utilizing a case-crossover study design, we explored the association between acute ozone exposure (maximum 8-hour daily average) and risk of stroke hospitalization among South Carolina residents and effect modification by race and gender. For total stroke (ischemic and hemorrhagic combined), a 10 ppb increase in ozone exposure on the day of hospitalization was associated with an increased risk of stroke hospitalization (OR: 1.08; 95% CI, 1.06, 1.11). Effects were similar for other lag days; however, the association was strongest for lag days 0-6 (OR: 1.20; 95% CIs 1.16, 1.24). We observed subtle differences in total stroke risk by gender, with females having a slightly lower risk than males, although CIs overlapped considerably. For hemorrhagic stroke, there was evidence of effect modification by race for all time periods of ozone exposure considered.Item Air Pollution Response to Changing Weather and Power Plant Emissions in the Eastern United States(2008-11-20) Bloomer, Bryan Jaye; Dickerson, Russell R; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Air pollution in the eastern United States causes human sickness and death as well as damage to crops and materials. NOX emission reduction is observed to improve air quality. Effectively reducing pollution in the future requires understanding the connections between smog, precursor emissions, weather, and climate change. Numerical models predict global warming will exacerbate smog over the next 50 years. My analysis of 21 years of CASTNET observations quantifies a climate change penalty. I calculate, for data collected prior to 2002, a climate penalty factor of ~3.3 ppb O3/°C across the power plant dominated receptor regions in the rural, eastern U.S. Recent reductions in NOX emissions decreased the climate penalty factor to ~2.2 ppb O3/°C. Prior to 1995, power plant emissions of CO2, SO2, and NOX were estimated with fuel sampling and analysis methods. Currently, emissions are measured with continuous monitoring equipment (CEMS) installed directly in stacks. My comparison of the two methods show CO2 and SO2 emissions are ~5% lower when inferred from fuel sampling; greater differences are found for NOX emissions. CEMS are the method of choice for emission inventories and commodity trading and should be the standard against which other methods are evaluated for global greenhouse gas trading policies. I used CEMS data and applied chemistry transport modeling to evaluate improvements in air quality observed by aircraft during the North American electrical blackout of 2003. An air quality model produced substantial reductions in O3, but not as much as observed. The study highlights weaknesses in the model as commonly used for evaluating a single day event and suggests areas for further investigation. A new analysis and visualization method quantifies local-daily to hemispheric-seasonal scale relationships between weather and air pollution, confirming improved air quality despite increasing temperatures across the eastern U.S. Climate penalty factors indicate amplified smog formation in areas of the world with rising temperatures and increasing emissions. Tools developed in this dissertation provide data for model evaluation and methods for establishing air quality standards with an adequate margin of safety for cleaning the air and protecting the public's health in a world with changing climate.