The increase in global population witnessed over recent years poses major threats to the quality of the air we breathe. Coupled with population growth in many developed countries, often driven by immigration, there have been substantial increases in the populations of developing countries. At the same time, an increasing number of individuals live in urban environments. In order to assess risk of exposure to hazardous air pollutants (air toxics) in the inner city, where a susceptible population resides, data obtained from high school students in the New York and Los Angeles TEACH (Toxic Exposure Assessment: A Columbia-Harvard Study) studies, were analyzed, with the three main objectives to: 1). Assess, characterize, quantify and compare directly-measured personal air toxics exposures from New York and Los Angeles; 2). Assess, quantify and compare the concentrations and temporal and spatial variability of air toxics measured in the outdoor urban microenvironments of these two cities; 3). Determine if personal air toxics exposures could be modeled using available time-activity information, coupled with measured microenvironmental air pollution inputs. The main findings of this research revealed substantial differences between New York and Los Angeles in the quantity and quality of particle-associated personal air toxics exposures in these two cities. Students across cities exhibited similar levels of personal exposure to particulate matter (PM 2.5) and to high levels of sulfates (greater in Los Angeles than New York; both likely of vehicular traffic origin). Different patterns of exposure to particle-associated air toxics was observed in the two cities and across seasons. In New York, students demonstrated substantially higher exposures to iron, cobalt, and manganese, likely of subway origin, than their counterparts in Los Angeles, who exhibited higher exposures to calcium, aluminum, magnesium (likely of crustal origin). Across seasons, within cities, differences were also detected, with higher levels of air toxics exposures shown in New York in the winter than in the summer for nearly 80% of the analytes, similar to the general pattern (winter vs. fall) in Los Angeles. With respect to outdoor air toxics concentrations, in general terms, crustal sources of air toxics were detected in both cities, though in Los Angeles these levels tended to be higher than in New York, often significantly. Anthropogenic sources were evident in each of the cities to varying degrees. Sulfates were detected at comparable high levels across both cities, though the levels tended to be higher and variability of concentrations of this air pollutant was greater Los Angeles than New York, likely reflecting differences both in patterns of traffic and built environment. Various approaches taken to model spatial and temporal variability of outdoor air toxics concentrations using mixed procedures showed city-specific, spatial and temporal variance patterns of air toxics. Using location and time (day) inputs, in New York, Zn, Pt, and Sn were among the elements with highest spatial variability in the summer, whereas in the winter, Co and La (possibly of subway origin) showed high spatial-temporal variance. In Los Angeles on the other hand, highest spatial to temporal variance ratios were noted for Cs, Ni and K in the fall and Ni, As and Mg in the winter. Each city also revealed different patterns of temporally dominant air toxics, consistent with variable-in-time excursions in air toxics reflecting remote, upwind sources. Using regression modeling that accounted for the distribution of measured personal air toxics, coupled with available time-activity diary data from TEACH and assignment of those activities to specific measured microenvironments, modeling of personal exposures yielded generally strong coefficients of determination, explanatory power and could be cross-validated. Important findings included the role of the indoor environment in predicting personal exposures and the degree to which a small percentage of time spent in the transit environment could affect exposures to trace elements from this source. Although the majority of elements could be predicted in large part by indoor exposures, not simply as a reflection of outdoor air toxics concentrations, the inclusion of other microenvironments, in many cases substantially increased the predictive power of the models generated. The research pursued in this thesis project further details and underscores the risk of air toxics exposures of young residents of the inner city, which, unlike workplace and environmental standards that traditionally may have been based on single exposures, are characterized by exposures to low level complex mixtures of air toxics. In aggregate, these mixtures may have different health consequences than more intense single pollutant exposures. Data generated here may help to inform planning of air quality monitoring approaches in the inner city, as well as provide one template for predictive modeling of human exposures to air toxics in that complex environment, to reduce the need for direct personal measurements to assess exposure risk. This may ultimately contribute to approaches to mitigate air toxics exposures and its consequences for an expanding global population residing in the world's inner cities.

Thesis ( MPH.) --University of Limpopo, 2014 / The purpose of this study was to investigate the knowledge and practices among households at Ga-Mokgwathi Village regarding the disposal of mercury coated bulbs. Cross-sectional design with quantitative approach was used in this study. The study objectives were to determine the knowledge about the disposal methods of mercury coated bulbs and also to determine the practices of handling broken mercury coated bulbs among the villagers of Ga-Mokgwathi. Data collection was done using self-administered questionnaires. Cluster random sampling was used in the study where a total number of 338 households were randomly selected to participate in the study. The results indicated that 36.7 % of the households at Ga-Mokgwathi Village had knowledge of safe disposal methods of mercury coated bulbs, 7.7% were not sure and 55.6% did not have such knowledge. Furthermore, the results indicated that 51.5% of the households had improper practices regarding the handling of broken mercury coated bulbs, 6.2% were not sure and 42.3% had proper practices regarding the handling of broken mercury coated bulb. The results of the study concluded that the majority of people were lacking knowledge of proper disposal methods and the handling of mercury coated bulbs. These results necessitate education of people about the disposal methods and handling of mercury coated bulbs.

This dissertation assesses the factors that lead to the emergence of infectious diseases in children, particularly the emergence of multidrug-resistant organisms (MDROs) and diarrheal pathogens in vulnerable pediatric populations. It includes three manuscripts. The initial study is a systematic review that summarized the role of antibiotic exposure on the acquisition of MDROs in children. Twenty-nine studies met the inclusion criteria and a positive association between prior antibiotic use and subsequent colonization or infection with an MDRO was identified in most studies. There were wide variations among study sites, populations, and definitions of antibiotic use and MDROs. Therefore, limited inferences could be made on which components of antibiotic exposure have the greatest impact on MDRO development. The second analysis examines the relationship between prior stay at a pediatric long-term care (LTC) facility and infection with an MDRO among hospitalized children. This study included 2,945 infections in 258,664 pediatric admissions from 2006 through 2016. At least 1 MDRO was identified in 10% of infections. Of the 1,198 children who had previously resided in a pediatric LTC facility, only 1 child (0.08%) had an MDRO infection. However, prior receipt of pediatric LTC was associated with an increased likelihood of infection (OR 2.4, CI95 1.66 – 3.43), C. difficile infection (OR 2.57, CI95 1.26 – 5.25), days of antibiotic use (OR 1.01, CI95 1.01 – 1.02), length of stay (OR 1.01, CI95 1.01 – 1.01), and death (OR 4.38, CI95 2.93 – 6.55). The concluding study evaluates the association between animals living in or near the home and diarrheal disease in children. This research is a secondary analysis of the Global Enteric Multicenter Study case control study, which investigated the epidemiology of diarrheal illness in children <5 in sub-Saharan Africa and south Asia. Of 9,439 cases and 13,128 controls, 87% had ≥1 animal in their home. In a multivariable analysis adjusting for exclusive breastfeeding, water source, sanitation facility, number of children <5 years in the household, and wealth index, any animal on a child’s compound decreased the odds of diarrhea by 33% (aOR 0.66, CI95 0.59 – 0.74). However, children with diarrhea who had an animal present were not more likely to have a positive stool culture. Overall, the three studies provide a thorough analysis of several factors associated with the infectious disease emergence in children, particularly as related to MDROs and diarrheal disease. Environmental characteristics, including antibiotic use and interaction with animals, were shown to be important factors for emergent infectious disease across diverse settings. The development of pediatric infection prevention interventions should take into consideration environmental risk factors in order to effectively mitigate the risks posed infectious disease emergence.

In 1990, the Clean Air Act (CAA) Amendments authorized the regulation of 188 hazardous air pollutants (HAP). Exposure to HAPs at sufficient concentrations and durations can increase both cancer and serious adverse non-carcinogenic effects. The purpose of this study was to conduct a human health risk assessment using data of 43 HAPs from five monitor sites in Portland, Oregon during July 1999-August 2000. HAP concentrations were compared to carcinogenic and non-carcinogenic (health) benchmark concentrations; and emission sources were determined for HAPs that exceeded health benchmark concentrations. Additionally, cancer risks were determined for subpopulations and compared to cancer risks generated for the general population. Results of this study indicate that 20 HAPs exceeded carcinogenic benchmark concentrations (corresponding to a risk level of 1 x 10������) in at least one location. Chromium compounds posed the highest cancer risk (3.5 x 10������). Seventeen HAPs exceeded carcinogenic benchmark concentrations at all five sites. Seventy-five percent (%) of the total cumulative cancer risk was contributed by chromium compounds, 1,3-butadiene, formaldehyde and 1,1,2,2-tetrachloroethane. Three HAPs, chromium compounds, acrolein, and formaldehyde, exceeded non-carcinogenic hazard ratios of 1.0. Releases from area sources accounted for the largest percentage of HAPs that exceeded health benchmark concentrations. With respect to subpopulations, asthmatics teenagers (age 11-16) and asthmatic adults (age 18-50), had slightly elevated cancer risks of 1.4 x 10������ and 1.2 x 10������. respectively, compared to the general population risk level of 1 x 10������. Results of this study indicate that several HAPs pose a potential human health concern in Portland and that efforts should be made to reduce their emissions. Additional studies are warranted to further assess potential human health risks and the extent of HAPs in Portland, Oregon. / Graduation date: 2003

The goal of the project was to develop a functional prototype of an environmental risk assessment parameter database on the World-Wide Web. The ability to develop a consolidated environmental database has become possible due to the phenomenal growth of the Internet and the World-Wide Web over the past few years. A large number of environmental resources do currently exist; however, with the large volume of information available, access, management, reliability, and retrievability have become increasingly difficult. To illustrate the prototype database, a practical environmental concern and the tools necessary to evaluate and characterize that concern were needed. Uranium (�������U) daughters leaching from abandoned mill tailing piles at three abandoned uranium mines in southwestern Colorado were chosen to demonstrate the database concept. The RESRAD environmental pathway modeling code served as the evaluation and characterization tool. Due to the size and complexity of RESRAD, a single radionuclide release rate equation was isolated as a controllable component of the code. The equation was a small part of the water pathway factor and examined the rate at which radionuclides absorbed in soil were leached by infiltrating water. This serves as the source term for groundwater contamination and directly applies to the �������U progeny leaching from mill tailing piles scenario. Parameters selected from the equation dealt with the background data that directly influenced the mobility of contaminates in the environment. Environmental data for the three Colorado sites were gathered and interpreted. Probability Density Functions (PDFs) were developed for input parameters and the results were then incorporated into the web site. / Graduation date: 1998

Quantitative soil ingestion studies employing a mass balance tracer approach have been used to determine soil ingestion rate for use in human health risk assessments (HHRAs). Past studies have focused on soil ingestion in populations living in urban/suburban environments and the results have been highly variable. Moreover, there is a paucity of reliable quantitative soil ingestion data to support human health risk assessments of other lifestyles that may be predisposed to ingesting soil, such as indigenous populations following traditional lifestyles. Thus, the primary objective of the research was to determine if populations following lifestyles typical of traditional land use practices in rural or wilderness areas ingest more soil than populations living in urban or suburban environments. Further, the research investigated the use of alternative mass balance tracers, specifically isotopes of the 238U and 232Th decay series, to reduce soil ingestion estimate variability. Mass balance tracer methods were developed and validated in a pilot canine study, and methods using isotope tracers were adapted to permit quantification of sediment ingestion in the benthic fish Moxostoma macrolepidotum (Shorthead Redhorse Sucker). A pilot human soil ingestion study of 7 subjects from an Aboriginal community in British Columbia was conducted over a 3-week period. The mean soil ingestion rate calculated using the daily means of the 4 elemental tracers with the lowest food-to-soil ratios (i.e., Al, Ce, La, Si) was observed to be approximately 74 mg d-1 (standard deviation 91 mg d-1), The median soil ingestion rate was 60 mg d-1, and the 90th percentile was 196 mg d-1. These soil ingestion rate estimates are higher than those currently recommended for HHRAs of adults, and higher than those obtained in most previous studies of adults. However, the estimates are much lower than the earlier qualitative assessments for subsistence lifestyles (i.e., 330-400 mg d-1). The study results also demonstrated that isotopes of the 238U and 232Th decay series radionuclide are not reliable mass balance tracers for estimating soil ingestion in humans; however, they may be useful for quantifying soil and sediment ingestion in wildlife.

Health risk assessment tools compute an individual’s risk of developing a disease. They are potentially useful in chronic disease prevention mediated by family physicians. We sought to learn family physicians’ awareness, and perspectives on the usefulness, usability and feasibility of implementation of risk assessment tools. Focus groups, discussion with key informants, and usability testing with an EMR-embedded risk assessment tool were conducted with family physicians (n=30) from academic and community-based practices. Analysis following grounded theory methodology was used to generate categories and themes. Our findings indicate that participants are aware of the implications of risk assessment calculations though very few tools are used regularly. Tool integration with EMR systems was felt to be essential in assisting tool usability, uptake and efficiency of use. Results provide insight into current risk assessment tool use and the facilitation of wider implementation of risk assessment tools in family practice settings.

Health risk assessment tools compute an individual’s risk of developing a disease. They are potentially useful in chronic disease prevention mediated by family physicians. We sought to learn family physicians’ awareness, and perspectives on the usefulness, usability and feasibility of implementation of risk assessment tools. Focus groups, discussion with key informants, and usability testing with an EMR-embedded risk assessment tool were conducted with family physicians (n=30) from academic and community-based practices. Analysis following grounded theory methodology was used to generate categories and themes. Our findings indicate that participants are aware of the implications of risk assessment calculations though very few tools are used regularly. Tool integration with EMR systems was felt to be essential in assisting tool usability, uptake and efficiency of use. Results provide insight into current risk assessment tool use and the facilitation of wider implementation of risk assessment tools in family practice settings.

Quantitative soil ingestion studies employing a mass balance tracer approach have been used to determine soil ingestion rate for use in human health risk assessments (HHRAs). Past studies have focused on soil ingestion in populations living in urban/suburban environments and the results have been highly variable. Moreover, there is a paucity of reliable quantitative soil ingestion data to support human health risk assessments of other lifestyles that may be predisposed to ingesting soil, such as indigenous populations following traditional lifestyles. Thus, the primary objective of the research was to determine if populations following lifestyles typical of traditional land use practices in rural or wilderness areas ingest more soil than populations living in urban or suburban environments. Further, the research investigated the use of alternative mass balance tracers, specifically isotopes of the 238U and 232Th decay series, to reduce soil ingestion estimate variability. Mass balance tracer methods were developed and validated in a pilot canine study, and methods using isotope tracers were adapted to permit quantification of sediment ingestion in the benthic fish Moxostoma macrolepidotum (Shorthead Redhorse Sucker). A pilot human soil ingestion study of 7 subjects from an Aboriginal community in British Columbia was conducted over a 3-week period. The mean soil ingestion rate calculated using the daily means of the 4 elemental tracers with the lowest food-to-soil ratios (i.e., Al, Ce, La, Si) was observed to be approximately 74 mg d-1 (standard deviation 91 mg d-1), The median soil ingestion rate was 60 mg d-1, and the 90th percentile was 196 mg d-1. These soil ingestion rate estimates are higher than those currently recommended for HHRAs of adults, and higher than those obtained in most previous studies of adults. However, the estimates are much lower than the earlier qualitative assessments for subsistence lifestyles (i.e., 330-400 mg d-1). The study results also demonstrated that isotopes of the 238U and 232Th decay series radionuclide are not reliable mass balance tracers for estimating soil ingestion in humans; however, they may be useful for quantifying soil and sediment ingestion in wildlife.

Real-world problems especially the ones that involve natural systems are complex and they are composed of many non-deterministic components. Uncertainties associated with these non-deterministic components may originate from randomness or from imprecision due to lack of information. Until recently, uncertainty, regardless of its nature or source has been treated by probability concepts. However, uncertainties associated with real-world systems are not limited to randomness. Imprecise, vague or incomplete information may better be represented by other mathematical tools, such as fuzzy set theory, possibility theory, belief functions, etc. New approaches which allow utilization of probability theory in combination with these new mathematical tools found applications in various engineering fields. Uncertainty modeling in human health risk assessment and groundwater resources management areas are investigated in this thesis. In the first part of this thesis two new approaches which utilize both probability theory and fuzzy set theory concepts to treat parameter uncertainties in carcinogenic risk assessment are proposed. As a result of these approaches fuzzy health risks are generated. For the fuzzy risk to be useful for practical purposes its acceptability with respect to compliance guideline has to be evaluated. A new fuzzy measure, the risk tolerance measure, is proposed for this purpose. The risk tolerance measure is a weighed average of the possibility and the necessity measures which are currently used for decision making purposes. In the second part of this thesis two decision making frameworks are proposed to determine the best groundwater resources management strategy in the Savannah region, Georgia. Groundwater resources management problems, especially ones in the coastal areas are complex and require treatment of various uncertain inputs. The first decision making framework proposed in this study is composed of a coupled simulation-optimization model followed by a fuzzy multi-objective decision making approach while the second framework includes a groundwater flow model in which the parameters of the flow equation are characterized by fuzzy numbers and a decision making approach which utilizes the risk tolerance measure proposed in the first part of this thesis.