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.

This dissertation consists of three essays. The first essay studies how health risk affects individuals' economic decisions due to changes in productivity, required medical expenditures, available time and survival probabilities implied by changes in health status. It assesses the role of these four channels in determining labour supply, asset accumulation and welfare using a life-cycle model calibrated to the U.S. economy. I find that all channels and the interactions between them have large implications for the macroeconomic variables studied. Health has larger effects for the non-college than college educated, explaining a significant fraction of the difference in labour supply, degree of reliance on government transfers and asset accumulation across education groups. Improving non-college health outcomes to approach those of college graduates results in large welfare gains, higher labour supply, and significantly lower reliance on government welfare programs. The second essay studies the evolution of wage inequality in the United States between 1980 and 2002 in a framework that accounts for changes in the employment of physical and cognitive skills and their returns. I find that within education-gender groups, average employed cognitive skills have remained constant, while average physical skills have declined. The returns to high levels of cognitive skills have increased dramatically, while returns to low levels of cognitive skills and physical skills have remained approximately constant. Skills account for approximately half of the increase in the college wage premium, and for a small but growing fraction of residual wage inequality. The final essay studies the sorting decisions of students with different levels of analytical and verbal skills into college fields of study. I build a model where each field tests and perfectly reveals to potential future employers only the students' skill that is intensively required in that field. Students' expected wages after graduation are a function of their revealed skill levels and firms' expectations of the unrevealed skills given the chosen field. I show how the size of each field and the average talent it attracts depend on the average skill levels, on skill dispersion and on the degree of correlation between skills in the student population.

Biosolids are valuable products which can be beneficially used in land application. However, the possibility of serious health effects on humans due to several pollutants in biosolids creates a big concern. To address this issue, risk-based methodologies are commonly used to evaluate health effects associated with the land application of biosolids. This study aims to investigate the health risks associated with ingestion of biosolids or soil mixed with biosolids by a child. This study is the first health risk assessment study in Turkey for land application of biosolids. Monthly sludge samples taken from Ankara Central Wastewater Treatment Plant (ACWWTP) in 2012 were analyzed for seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb, and Zn), and two organic contaminants (PCB and NPE) concentrations. To calculate health risks, methodologies developed by U.S. Environmental Protection Agency (U.S. EPA) and French National Institute for Industrial Environment and Risks (INERIS) were used. With both methods, cancer and non-cancer risks for the ingestion by a child pathway were determined and found to be below the acceptable cancer and non-cancer risk levels suggested by U.S. EPA and INERIS. Additionally, same health risk calculations were conducted for sludge and soil limit values provided in Turkish Regulation for the Use of Sewage Sludge in Agriculture (2010) to determine what the maximum health risk would be for the worst case scenario in Turkey. According to the results, even if the concentrations are at the maximum possible regulatory levels, the health risks are still low.

This dissertation consists of three essays. The first essay studies how health risk affects individuals' economic decisions due to changes in productivity, required medical expenditures, available time and survival probabilities implied by changes in health status. It assesses the role of these four channels in determining labour supply, asset accumulation and welfare using a life-cycle model calibrated to the U.S. economy. I find that all channels and the interactions between them have large implications for the macroeconomic variables studied. Health has larger effects for the non-college than college educated, explaining a significant fraction of the difference in labour supply, degree of reliance on government transfers and asset accumulation across education groups. Improving non-college health outcomes to approach those of college graduates results in large welfare gains, higher labour supply, and significantly lower reliance on government welfare programs. The second essay studies the evolution of wage inequality in the United States between 1980 and 2002 in a framework that accounts for changes in the employment of physical and cognitive skills and their returns. I find that within education-gender groups, average employed cognitive skills have remained constant, while average physical skills have declined. The returns to high levels of cognitive skills have increased dramatically, while returns to low levels of cognitive skills and physical skills have remained approximately constant. Skills account for approximately half of the increase in the college wage premium, and for a small but growing fraction of residual wage inequality. The final essay studies the sorting decisions of students with different levels of analytical and verbal skills into college fields of study. I build a model where each field tests and perfectly reveals to potential future employers only the students' skill that is intensively required in that field. Students' expected wages after graduation are a function of their revealed skill levels and firms' expectations of the unrevealed skills given the chosen field. I show how the size of each field and the average talent it attracts depend on the average skill levels, on skill dispersion and on the degree of correlation between skills in the student population.

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.

Health risk behaviors are responsible for the majority of morbidity and mortality among adolescents. Researchers have identified three sources of risk-taking in adolescents – dispositional, ecological and biological. The Bioecological Model incorporates these three sources of risk-taking, however it lacks explanatory power. For this reason, this thesis focused on explaining risk perception of health risk behaviors (smoking cigarette, alcohol and marijuana use), and health risk behaviors by integrating the Bioecological Model with a more specific Health Belief Model. The relationship between risk perception and health risk behavior was also investigated as a first step in understanding adolescent decision-making using the Health Belief Model. Adolescents from a suburban Indiana area were asked to complete the Adolescent Health Risk Behavior Survey which assessed egocentrism, self-esteem, social norms, risk perceptions, and the incidence and prevalence of health endangering behaviors. Hierarchical linear regression was used to determine the ability of the systems in the Bioecological Model and their specific variables to explain risk perception of health risk behaviors. Hierarchical logistic regression was used to determine the ability of the systems in the Bioecological Model and their specific variables to explain health risk behaviors and to moderate the relationships between risk perception and health risk behaviors. Based on the results, it was confirmed that the Bioecological Model is important in understanding adolescent’s risk perception of health risk behaviors, and their self-reported health risk behaviors. It is also important in understanding the relationship between risk perception and health risk behaviors. Adolescent Variables, Microsystem, and Mesosystem were significant in predicting adolescent risk perception of all health risk behaviors examined, and self-reported smoking cigarette behavior and marijuana use. Adolescent variables and Microsystem were the only systems to predict adolescent self-reported alcohol use. The relationship between risk perception and reported smoking cigarette behavior was moderated by Adolescent Variables, Microsystem and Mesosystem, however for alcohol use the path was moderated by Adolescent Variables and for marijuana use the path was moderated by the Mesosytem. Results of this thesis imply the importance of considering the contribution of Bioecological Model variables when implementing prevention intervention programs specific to adolescent health risk behaviors.

The objective of this study was to investigate the exposure assessment and health risk of particulate matter emitted from steel industry for high-risk inhabitants living in metro Kaohsiung. A steel plant and an electric arc plant were selected for conducting the sampling of particulate matter (PM). The physical and chemical properties of PM sampled at the working place and at the fence of selected plants were also analyzed to establish the fingerprints of PM in the steel industry. In order to accomplish this study, both personal sampling and environmental sampling were conducted in steel plants. Personal exposure sampling was undertaken at working places, while the conduction of environmental sampling might affected by various uncertain environmental factors (such as meteorological condition and other emission sources), but it could characterize the overall environmental situation and help exposure assessment. Moreover, The exposure of employers (including manufacturing workers and supporting staffs) could be further assessed based on the concentration and duration of PM exposure. Specific metal concentration was obtained from working environment, searching for exposure parameter (such as exposure frequency, exposure duration, body weight, average time, and etc.) and toxicity database (e.g. cancer slope factor and reference dose). The data could be used for assessing both cancer risk and non-cancer risk of specific heavy metal. Sampling data obtained from working places showed that the highest PM concentration were observed during the electric arc process, especially the charging and discharging procedures. The concentration of PM1.0, PM10, and TSP at the working places were 53.3~195.6 £gg/m3 ,365.7~550.0 £gg/m3, and 1085.5~2755.0 £gg/m3, respectively. Measured at the outdoor environments of working places, the highest PM10 and TSP concentration, ranging from 365.7~550.0 £gg/m3 and 1085.5 ~2755.0 £gg/m3, were observed at the sinter plants of a steel manufacturer. Sampling data obtained at the fence of steel plants (a steel plant and electric arc plant) indicated that the concentration of PM10 and TSP exceeded the ambient air quality standards. Modification of manufacturing process and improvement of PM collection system are highly required to reduce the concentration level as well as the emission of PM. Results of fingerprint of PM (PM2.5, PM2.5-10, TSP) obtained from working places showed that iron, calcium, sulfate, nitrate, calcium ion, and elemental carbon were the major chemical content of PM at the melting plant, the sinter plant, and the storage field. While, iron, calcium, sulfate, nitrate, calcium ion, and organic carbon were the major chemical content of PM at electric arc plant. Results of personal exposure concentration and exposure dose of PM showed that the highest exposure level of both manufacturing workers and supporting staffs were observed at the storage field, while the lowest exposure level was found at the sinter plant. Therefore, enforcement of wearing maskers and/or shelters at the storage field is also highly recommended to prevent manufacturing workers from the exposure of high-level PM at working places. Moreover, the cancer risk of manufacturing workers exposured to hexavalent chromium (Cr6+) at the melting plant, the sinter plant, the storage field, and the electric arc plant exceeded acceptable cancer risk standard (10-5~10-6), while the hazard index of manganese (Mn) was much higher than other metals.Meanwhile, exposuring to Cr6+, Ni, and Mn at the electric arc plant also exceeded acceptable standards (Cr6+ and Ni¡G10-5~10-6 , Mn¡G1). Several control strategies, including pollution reduction measures such as the usage of clean fuel, process modification, the improvement of collection system, the enhancement of manufacture management, the conduction of environmental monitoring and exposure assessment, floor cleanup and truck entrance management, are recommended to improve the contamination of PM at working places and surrounding environments for metallurgic industries. Moreover, enforcement of wearing maskers and/or shelters at high-risk environments is also highly recommended to prevent manufacturing workers from the exposure of high-level PM at working places. Keywords: steel industry, particulate matter sampling, physical and chemical characteristics, exposure assessment, health risk