Browsing by Subject "Environmental Health"
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Item Application of restaurant inspection data analysis to increase assurance of food safety.(2012-05) Petran, Ruth LindenthalFoodborne illness affects 48 million Americans annually with the majority of reported foodborne outbreaks due to food prepared and served by restaurants. Food safety practices at restaurants are verified via periodic inspections by health department personnel. With millions of such inspections conducted every year, concentrating on the most frequently identified risk factors could focus interventions where they will have the most impact. This would be particularly beneficial for restaurant chains with establishments across the country. Compared in this study were recent health department inspections in Minnesota and Arizona that had been performed at restaurants known to have had confirmed outbreaks to matched control restaurants that did not have outbreaks during the same time period. No overall relationship to foodborne illness risk factors was demonstrated. However, a set of violations more likely to be associated with outbreak restaurants was identified. These violations likely represented a lack of overall control of food safety processes in the outbreak restaurants. There were differences in the specific violations identified between the two states, most likely attributable to the high variability in inspection approaches among different health department jurisdictions. The results highlight the need for a more consistent, nationwide approach to restaurant inspections than exists currently and suggest several approaches to improve the use of inspection data to reduce foodborne illness rates.Item Development of a semivolatile aerosol dichotomous sampler(2008-12) Kim, Seung WonThis dissertation consists of three main sections which report the procedures used to develop the semivolatile aerosol dichotomous sampler (SADS) and their results. The first section describes the theoretical background of SADS and the validation of its performance using numerical simulations and experimental data. SADS was proposed as an alternative method to overcome some of the problems of existing personal sampling methods such as evaporative loss during filter sampling. The main difference between virtual impactors and the SADS was the inverted flow ratio between the major and the minor flow. Sampling in the SADS settings gave a lower cutsize in both numerical simulations and experimental results. The second section reports the results of an optimization procedure for SADS and experimental confirmation with the optimized sampler. Using numerical modeling, the relationships between four major design and operating parameters significantly affecting the performance of the SADS and four performance parameters were expressed in polynomial equations. Utilizing an optimization procedure, values for the major parameters giving the best performance were determined and used as the base model for optimizing minor parameters. Five minor parameters were then investigated for their possible contribution to better performance of the SADS. Experimental tests confirmed that the performance of the new sampler was improved although not as much as expected from the numerical simulation. In the third section, the sampling performance of SADS was compared with existing vapor and particle sampling methods. Seven different test fluids were used to generate test droplets and the concentrations and composition in each phase were evaluated using gas chromatography. Combined vapor and particle concentrations for each test aerosol were not statistically different from one another as a function of test method. However, the particle concentrations estimated using the SADS were statistically higher than those from the other methods. In the tests of a chemical mixture and oil mists, a similar pattern of vapor/particle concentration ratio to the individual compounds was observed. SADS worked better than a filtration method and measured higher particle concentrations than other methods.Item Distribution of mycotoxins in fungal structures(2011-06) Errede, Dawn C.Exposure to mycotoxins associated with small fungal fragments may cause adverse health effects. Current air sampling methods may not detect such fragments and may cause researchers to underestimate fungal exposures. Understanding how time and substrate affect the distribution of toxins and their release into the environment can strengthen estimates of potential risks of exposure to these toxin-carrying particles. This research investigated the influence of time and growth substrate on the amount and distribution of mycotoxins in fungal structures and particles released from the fungal colonies. A common, toxin-producing, indoor mold, Aspergillus versicolor, was inoculated on two different agars: Malt Extract (MEA) and Wallpaper Paste (WPA). Fungal material was collected both by coring the plates, and by washing the plates with sterile water and glass beads at weekly intervals from one to six weeks. The wash water suspensions were filtered through 20- and 1-micron filters and lyophilized. The filters and the lyophilized wash water samples were extracted with methanol and analyzed for both sterigmatocystin and ergosterol (a marker of fungal growth). Results indicate that overall growth and toxin levels are higher on MEA than on WPA, but when standardized against ergosterol, sterigmatocystin levels on WPA are higher. Measurable amounts of ergosterol and sterigmatocystin are detectable in the lyophilized wash water. Ergosterol and sterigmatocystin increase steadily over six weeks on WPA, but peak around 3-4 weeks on MEA. Our conclusions are that small fungal fragments can carry toxins at levels that could deliver biologically significant doses if the fragments were inhaled into the deep lung.Item Documenting perceptions about pesticides and other environmental exposures with photovoice : mothers' concerns for their children(2008-11) Stedman-Smith, Margaret M.Women of childbearing age and children living in rural agricultural regions are at-risk for pesticide exposure from a variety of pathways including occupational track-in, drift from farming activities, residential usage, and dietary intake. The purpose of this dissertation research is to answer the questions: "What do mothers perceive as pesticide exposure pathways for themselves and their children? How do these perceptions differ between cultural groups?" The study involves a secondary analysis of data collected during the summer of 2007 in the Red River Basin of the North from the University of Minnesota's Regional Sustainable Development Partnerships and the Division of Environmental Health Sciences. Sixteen women from three diverse groups participated: Caucasians enrolled in the Women Infant and Children federally subsidized nutrition program, new American immigrants, and Native Americans. Due to culture, economics, and geography, these groups may experience increased health risks from pesticide exposure. Photovoice was used as a qualitative methodology to document mothers' concerns about pesticide exposure and other health issues for their children, since it enables participants, including those who lack verbal acumen in the language of the dominant culture, to use photographs to address questions like, "Why does this situation exist? Do we want to change it, and, if so, how?" Caucasian and Native American mothers voiced concern about pesticide exposure from drift due to agricultural spraying on the ground and by plane. All participants wanted advanced notice to take precautionary measures before fogging or spraying. Perceptions of pesticide exposure differed according to the cultural lens of each group: Caucasian women saw the necessity of industrial agriculture and pesticide usage as a trade-off; Native American women voiced concerns about pesticide contamination to traditional foods; and new American immigrants expressed a need to learn how to read labels and use pesticides safely. Participants suggested culturally congruent strategies for the delivery of educational information. Consumption of locally grown organic foods was identified as one strategy to reduce pesticide exposure. This research assists public health professionals, extension educators, and primary care providers with the aim of reducing pesticide exposure to children living in rural agricultural regions.Item The etiology and consequences of injuries to veterinary technicians.(2009-11) Nordgren, Leslie DianneApproximately 53,000 Certified Veterinary Technicians (CVTs) are at risk of traumatic occupational injuries (Bureau of Labor Statistics, 2004) that are costly in terms of medical expenses, lost work time, and career loss. A two-phase study, using mailed questionnaires, identified total injury experience and consequences and risk factors for animal bites among all 1,427 Minnesota CVTs. Methods . Phase 1 comprehensive data were collected on injury events, consequences, and exposures from the previous 12 months (74% response) to identify annual injury rates and potential risk factors. Phase 2, a nested case-control study, examined relations between exposures and animal bites in small animal clinics that CVT cases (n=176) reported in the previous 12 months; controls (n=313) reported no bites. Exposure data were collected from cases (month prior to the bite injury) and controls (randomly selected months) (61% response) to facilitate multivariate analyses, based on Directed Acyclic Graphs. Results - In Phase 1 (873 respondents), 1,827 injury events were reported by 445 CVTs. Injury rates (95% Confidence Intervals) per 100 persons per year included all injuries, 236.8 (226.2 . 247.9) and bites, 77.7 (71.7 . 84.2). Increased rates involved: <6 years handling animals; ≤ 3 years working as a CVT; working in small animal clinics. Primary injury types were bites, cuts/lacerations/scratches, and contusions, and leading sources were cats and dogs involving animal restraint or treatment. Consequences included: treatment, restricted work, and lost work time. Multivariate modeling identified a decreased risk for working <40 hours/week and increased risks for: handling >6 types of animals per day; handling animals <6 years; and working in emergency clinics; or small animal clinics. Phase 2 multivariate analyses indicated increased risks of bite injury for: age <35 years versus 35+; <5 versus 10+ years experience; "frequently" and "infrequently to never" versus "always," having adequate help; handling 5+ versus <3 animal types per day; and decreased risks for no prior bite injury history) and handling <10 versus 20+ animals per day. Conclusions . The CVTs' environment places them at risk of injuries with serious consequences. In addition to documented risks, further examination of relevant exposures is integral to the development of relevant interventionsItem Evaluating bias caused by screening in observational risk-factor studies of lung cancer nested in the PLCO randomized screening trial.(2009-09) Jansen, Ricky JeffreyIt is well-known that bias such as lead-time and length distort studies of screening efficacy whether survival or incidence is of interest. A third bias, usually called overdiagnosis bias, occurs when an individual is only diagnosed with disease before death from a different cause because he/she is screened. These forms of bias can also arise in observational studies where the proportion screened and screening rates vary by risk-factor strata. This difference in screening behaviors influences corresponding case ascertainment or case enrollment probabilities which can lead to erroneous conclusions about the size of the risk-factor effect on the disease. It has been suggested that classic confounding occurs in such risk-factor studies when screening is efficacious; therefore, it can be addressed by conventional analyses such as stratification or confounder adjustment in regression models. However, even if the test is not efficacious, screening creates changes in case ascertainment probabilities which must be addressed using alternative methods. Recurrence-time models, long used for screening programs, can be adapted to model the affect screening use has on risk-factor studies. These models can be used to study the magnitude of potential bias, but may also be adapted to provide an analytic approach to correct estimates for such bias. The risk-factor studies nested in the PLCO trial are potentially affected by such bias, and this randomized study also provides a structure within which models of screening bias may be tested and validated. To validate our model, a variety of nested case-control studies will be developed that measure the effect smoking has on lung cancer and the degree to which the bias affecting those estimates change based on the study design will be determined. This process will include a) expanding a previously developed lead-time bias model to incorporate length and overdiagnosis; b) incorporating a more flexible and realistic model of screening that can incorporate the patterns documented in the PLCO trial; c) exploring if the mathematical model is valid using varied nested study designs within PLCO and comparing resulting logistic regression estimates to simulated results; and d) using the validated models to produce correction factors for use in other nested risk-factor studies. Results indicate that the mathematical model is highly sensitive to overdiagnosis as increasing rates increase expected bias, but relatively insensitive to using different screening test sensitivities. Increasing screening behavior differential during the study, preclinical duration length, and selecting from the intervention group are associated with increasing expected screening bias. Increasing screening behavior before the study and selecting from the usual-care group are associated with a decreasing expected screening bias. Although the mathematical model couldn't be validated as a correction factor here, the results suggest using a shorter preclinical duration distribution for the model may produce more accurate screening bias values. The focus of this work was to identify if chest x-ray screening could modify the estimated risk of smoking on lung cancer diagnosis. An additional goal was to develop a usable method for adjusting observational studies of lung cancer for the bias arising from differential chest x-ray screening between ever and never smoking groups. In a boarder sense, this work has provided an explanation of the effect screening use may have on an observational risk-factor study and an example of how to implement the mathematical technique. Additionally, this project has provided a more general method for doing sensitivity analyses on the screening related assumptions involved with these studies, whether nested in a randomized trial or sampled from the population at large.Item Evaluating Health and Healthcare Use Effects of Changes in Paid Sick Leave Access for Workers in the United States(2016-10) Klein, RyanBackground: The United States is one of the only industrialized countries without a nationwide mandatory paid sick leave policy, which would give workers the ability to take time off work for their own health or the health of their children without jeopardizing their job standing or income. Taking time away from work to rest when sick has been shown to promote quicker recovery and prevent the transmission of illness and the progression of minor illnesses into more serious illnesses1; paid sick leave allows time for this rest without financial consequences to the employee. When workers are chronically ill, not being able to seek care could mean that they are not able to adequately care for their chronic disease. Although the health and work absence effects of having access to paid sick leave have previously been studied, they have not been investigated in a way that suggests causality. Paid sick leave also has the potential to affect how people use the healthcare system. Being able to take time off from work for the purposes of caring for health leads to quicker recovery and prevention of the progression of minor illnesses into more serious illnesses. It also helps to alleviate some of the access barriers that are often associated with not being able to seek care at an office-based medical provider by freeing up time during normal business hours to seek care without foregoing income. As a result, paid sick leave could help to control the amount of non-urgent emergency department (ED) visits, which are increasingly becoming an issue in EDs across the United States. Objective: The overall objective of this research is to determine the effect that paid sick leave has on work-absence behavior, general health, and healthcare use behavior for workers in the United States, with an additional focus on the subset of workers with chronic illnesses. Manuscript 1: Aim: Determine the effect of paid sick leave on work-absence behavior and general health status for workers in the United States, with an additional focus on workers with chronic illnesses. Methods: Fixed and random effects models were used with longitudinal data from the Medical Expenditure Panel Survey to model the effect of paid sick leave on work-absence behavior, and subsequently on the effect of work-absence behavior on general health status, both for our full sample of workers, and also for a chronically ill subset of workers. Results: Our overall results showed that paid sick leave does not have a large effect on self-reported general health status, and these results held consistent in both the full analysis sample as well as the chronically ill subsample. Our results also showed that the effect of paid sick leave on work absence days very much depends on the context with which the worker has paid sick leave – whether it is being gained and compared to those that workers never had paid sick leave, or it was held for the entire follow-up period and being compared to those that lost the benefit at some point during follow-up. Manuscript 2: Aim: Determine the effect of paid sick leave on emergency department use and office-based medical provider use volume for workers in the United States, with an additional focus on workers with chronic illnesses. Methods: Fixed effects models were used with longitudinal data from the Medical Expenditure Panel Survey to model the effect of paid sick leave on the volume of emergency department use and office-based medical provider use, both for our full sample of workers, and also for a chronically ill subset of workers. Results: Our results showed that the effect of paid sick leave on office-based medical provider use volume depended on whether the benefit had been gained and was being compared to participants that never had it, or instead had been lost over the course of follow-up and was being compared to participants that had never lost the benefit. Those that gained the benefit had less office-based medical provider visits as compared to those that never had paid sick leave, while those that had the benefit for the entire follow-up had more office-based provider visits compared to those that lost it, both for the full sample of workers and the chronically ill subset. Our results also showed that the effect of paid sick leave on emergency department use volume depended predominantly on whether we investigated the effect in the full analysis sample, or within the subset of chronically ill workers. While the full analysis sample showed no effect of paid sick leave on office-based medical provider use volume in either subsample, both subsamples in the chronically ill subset of workers showed an increase in the number of visits when those with paid sick leave were being compared to those without Conclusion: These analyses present a more nuanced and rigorous approach to analyzing the effects of paid sick leave on health, work absence behavior, and healthcare use behavior than previously existed in the literature. By performing analyses using longitudinal data, we were better able to approximate the counter-factual than previous studies on these topics, which all utilized some form of cross-sectional data. Additionally, these analyses filled an important literature gap by investigating the effects of paid sick leave on our outcomes of interest in a subset of workers with chronic illnesses, an analysis that had not been reported in the literature yet to date.Item Formation of perfluorooctane sulfonate on suspended water droplets via hydrolyzation of a volatile precursor.(2010-09) Lanners, Jeffrey MichaelPerfluroroctanesulfonate (PFOS) is a ubiquitous global pollutant with no known degradation pathways. A 2001 study by Kannan et al. helped to establish PFOS as a global contaminant by measuring it in wildlife and waterways in both remote and urban areas. Atmospheric transport is believed to be the main pathway by which PFOS has been spread globally. The low vapor pressure and high water solubility combine to provide PFOS with a low Henry’s Law Constant making direct atmospheric transport unlikely. One possible explanation for the atmospheric transport of PFOS involves transport and reaction of volatile precursors. Volatile precursors such as perfluorooctane sulfonyl fluoride (POSF) have been demonstrated to react with suspended aerosol water droplets resulting in the formation of PFOS. Underwater exposure of POSF resulted in significantly decreased PFOS production compared to aerosol droplets. This indicates the importance of an air water interface, which allows POSF to position itself so that the reactive sulfonyl head is on the surface of the water and the hydrophobic tail is oriented away. Experiments involving aprotic solvents indicate the diffusion of POSF into water is faster than simultaneous surface hydrolysis. In order to gain a better understanding of the role the air-water interface plays in PFOS production two parameters were varied independently. The volume of the aerosol droplets exposed and the duration of time they were exposed for was varied in separate experiments. Observations indicate that time plays a very important role in PFOS production, as longer exposed droplets contained less POSF than those exposed for shorter time periods.Item Negative regulation of oncogenic Ras signaling by mitogen-activated protein kinase phosphatase-3.(2010-07) Zeliadt, Nicholette A.Activating mutations in the Ras oncogene are found in ~30% of all human cancers. Ras is a central regulator of intracellular signaling pathways, such as the Raf/MEK1/2/ERK1/2 protein kinase cascade, that modulate cell cycle progression, cell proliferation, and cell survival. Chronic activation of Ras-stimulated pathways is believed to play a key role in cellular transformation, although constitutive activation of Ras alone is not sufficient for tumor development. The goal of these studies is to further understand the biochemical events that occur during carcinogenesis in cells that express activated Ras that make cells susceptible to tumor promoting stimuli. This knowledge is important for the development of new strategies to diagnose, prevent and treat cancer. To date, attempts at developing small molecule inhibitors of oncogenic Ras have been unsuccessful. Therefore, efforts have instead focused on targeting downstream effectors of Ras, such as the Raf/MEK1/2/ERK/12 cascade, or preventing the posttranslational prenylation of Ras that is critical for its function. The aim of these studies is two-fold: 1) to elucidate the signaling events that occur in cells exposed to tumor-promoting stimuli; and 2) to develop tools for the study of prenylation in living cells.Item Occupational exposure assessment for nanoparticles.(2009-08) Park, Ji YoungThis dissertation consists of four sections which address various aspects of assessing exposure to nanoparticles and monitoring methods. The first section examines the appropriateness of different exposure metrics using multiple-metric measurements that were carried out in multiple locations of workplaces generating incidental nanoparticles to construct aerosol maps. The concentration peaks of SA and fine particle number agreed more with locations of nanoparticle sources and showed larger concentration ratios between work areas than mass concentration. This indicates that SA and fine particle number concentrations are more appropriate for nanoparticle than mass. The second section examines the ability of various exposure metrics to distinguish between exposure categories. Multiple-metric measurements were obtained in high and low exposure zones in workplaces generating incidental nanoparticles. SA and fine particle concentrations showed higher `contrast' in mean concentrations and larger concentration ratios between zones than mass concentrations. The results suggest that SA and fine particle number concentrations are more efficient than mass for classifying worker exposures into categories. The results suggest that the choice of appropriate exposure metrics is critical for classifying workers into similarly exposed groups. In the third section, SA concentrations were estimated in two ways based on number and/or mass concentrations using aerosol instruments and compared with SA directly measured using a diffusion charger. Estimated SA was derived from particle size distribution by number and was calculated using a simple inversion method. Both estimated SA overestimated measured SA but were correlated with measured SA. The results suggest that the estimated SA may a good predictor of measured SA. In the fourth section, three SA estimating methods were applied and evaluated based on number and/or mass concentrations measured by readily available instruments. Estimated SA was derived from particle size distribution by number and was calculated using two different inversion procedures. The estimated SA was compared with the reference SA obtained from the scanning mobility particle sizer and optical particle counter. All estimated SA had qualitatively similar trends to the reference. The results suggest that all estimation methods may be used as an interim solution for the purpose of classifying exposure zones within a workplace.Item The occurrence and environmental fate of polybrominated diphenyl ethers and glyphosate in the atmosphere.(2010-08) Chang, Feng ChihThe net air-water exchange flux of polybrominated diphenyl ethers (PBDEs) in the Great Lakes and the atmospheric presence of glyphosate and aminomethylphosphonic acid (AMPA) in the farm fields are reported here for the first time. Paired air and surface water samples were collected during May and July from Lake Michigan in 2005 and Lake Superior in 2006. Average atmospheric PBDE concentrations and deposition were higher over Lake Michigan than Lake Superior and higher at nearshore urban than open-lake sites. Additionally, annual mass budgets of PBDEs for the Great Lakes are presented by estimating atmospheric deposition, wastewater treatment plant discharge, burial of lake sediments, and lake water outflow. The results indicated that annual mass budget of "6PBDE (BDE-47, 66, 100, 99, 154, and 153) for Lake Michigan was a net increase with 270 kg yr-1. In contrast, the budget for Lake Superior approached equilibrium with a net increase of 14 kg yr-1. Wet deposition was the major contributor (71-75%) of the total "6PBDE inputs to both lakes. Glyphosate and AMPA were detected only in the particle phase of air samples in Mississippi and Iowa in 2007-2008. The frequency of glyphosate detection ranged from 61 to 100% (in air) and 63 to 92% (in rain). The highest concentrations of glyphosate and AMPA in both air and rain were found during the periods of intense glyphosate applications. Glyphosate and AMPA were removed efficiently from the air by particle scavenging in rainfall events. Based on annual mass budgets of glyphosate in Mississippi and Iowa study sites, less than 0.1% of the applied glyphosate moved into the atmosphere due to application spray drift (0.01%-0.05%), and wind erosion (<0.01%-0.02%).Item Sleep patterns and risk of injury among rural Minnesota adolescents.(2009-08) Langner, Deborah MerchantSleep occupies a third of our lives; yet, only of late has credit been given to the significant role it plays in our health and well-being. Teens often are limited in the duration of sleep acquired, due to time-consuming activities, as well as biological and environmental aspects of adolescence. The current study explores potential risk of injury among teens by examining associations between sleep patterns, sleep duration, and injury. Youth at Work, an open cohort from 41 rural high schools in Minnesota, followed 15,002 students from 2001-2003. Data were collected through a self-completed questionnaire, distributed to each student four times during the 2001-2002 and 2002-2003 school years. Questionnaire responses described events in either the summer months (fall administration) or the school year (spring administration). A total of 41, 272 questionnaires were completed. Analysis included odds ratios (OR) and 95% confidence intervals (CI) calculations using logistic regression, controlling for potential confounders by means of directed acyclic graphs. Results indicated that adolescents who reported sleeping six hours or less every night during the summer had an increased risk of injury (OR = 1.40; CI = 1.13, 1.72). Risk of injury increased further for individuals who slept six hours or less during the weekend nights in the summer, but received optimal sleep on weeknights (OR = 1.60; CI = 1.20, 2.14). During the school year, students who reported six hours of sleep or less during school nights and sub-optimal sleep on weekend nights also had an increased risk of injury (OR = 1.53; CI = 1.07, 2.20), as did individuals who slept nine hours or longer on weekend nights but acquired insufficient sleep on school nights (OR = 1.71; CI = 1.22, 2.39). Among working adolescents, teens employed in entertainment who routinely slept six hours or less or greater than six hours but less than nine hours, had the greatest risk of work-related injury, compared with well-rested teens in this occupation (OR = 3.61; CI = 1.17, 11.09). Construction workers who slept either insufficient or sub-optimal hours also were nearly three times as likely to be injured as teens sleeping optimal hours (OR = 2.69; CI = 1.19, 6.06). Among farmers, risk of injury doubled for young adults who had insufficient sleep some nights, but slept optimally other nights (OR = 2.05; CI = 1.37, 3.07). Improved knowledge of these associations and potential risks could help to target intervention efforts for the prevention of injuries among adolescents.Item A Theoretical Framework for the Use and Interpretation of Molecular Subtyping in Foodborne Disease Surveillance(2008-05) Besser, John MitchellThe development of molecular subtyping for foodborne disease surveillance has significantly enhanced our ability to detect, investigate, and control common source outbreaks. Despite wide-scale use and many high profile outbreaks detected through enhanced foodborne disease surveillance, use and interpretation of molecular subtype data has been primarily intuitive. Efforts to develop interpretive guidelines have been based primarily on laboratory criteria with the relatively narrow goal of defining the likelihood of relatedness between strains. However, the significance of strain relatedness is context dependent, and additional factors are required for epidemiological inference. These factors have not been clearly defined, which has limited our ability to consistently interpret findings and effectively utilize the new tools. In this work, a theoretical framework was developed to describe the interrelationship of case definitions based on molecular or other classifications, the normal prevalence of disease or strain, frequency of exposure, specificity of exposure information, and number of cases in a common source outbreak setting. A computer model was developed to illustrate the impact of increasing case definition specificity and exposure prevalence on the association between illness and exposure. The model demonstrated that as the case definition in a case control study became more specific, measures of association increase and confidence intervals widened. Low prevalence exposures required less case definition specificity or fewer cases to reach significant association than high prevalence exposures. The model demonstrated that the optimum level of molecular subtype specificity is not fixed, but depended on the prevalence of the exposure, specificity of the exposure information, the number of available cases, and the question being asked. Furthermore, the sensitivity of exposure identification and the specificity of the exposure information have an impact on the ability to detect and resolve common source outbreaks in much the same manner as molecular subtyping. Using the key parameters identified, the inherent benefits and limitations of each of the currently available surveillance systems were compared for their ability to detect problems in the food supply. Interpretive guidelines for molecular subtype data were developed, and a practical guide to best practices was formulated.Item Understanding and strengthening exposure judgments using Bayesian integrated exposure assessment strategies.(2010-12) Logan, Perry WilliamAccurate exposure assessments are critical for ensuring that potentially hazardous exposures are properly identified and controlled. The availability and accuracy of exposure assessments can determine whether resources are appropriately allocated to engineering and administrative controls, medical surveillance, personal protective equipment and other programs designed to protect workers. A desktop study was performed using videos, task information and sampling data to evaluate the accuracy and potential bias of participants' exposure judgments. Desktop exposure judgments were obtained from occupational hygienists for material handling jobs with small air sampling data sets (0-8 samples) and without the aid of computers. In addition, data interpretation tests were administered to participants where they were asked to estimate the 95th percentile of an underlying lognormal exposure distribution from small data sets. Participants were presented with an exposure data interpretation or rule-of-thumb training which included a simple set of rules for estimating 95th percentiles for small data sets from a lognormal population. Results of each data interpretation test and qualitative and quantitative exposure judgments were compared with a reference judgment obtained through a Bayesian probabilistic analysis of the sampling data to investigate overall judgment accuracy and bias. There were a total of 4,386 participant-task-chemical judgments for all data collections: 552 qualitative judgments made without sampling data and 3,834 quantitative judgments with sampling data. The data interpretation tests and quantitative judgments were significantly better than random chance and much improved by the rule of thumb training. In addition, the rule of thumb training reduced the amount of bias in the data interpretation tests and quantitative judgments. The mean data interpretation test % correct scores increased from 47% to 64% after the rule-of-thumb training (p<0.001). The accuracy for quantitative desktop judgments increased from 43% to 63% correct after the rule-of-thumb training (p<0.001). The rule of thumb training did not significantly impact accuracy for qualitative desktop judgments. The finding that even some simple statistical rules of thumb improve judgment accuracy significantly suggests that hygienists need to routinely use statistical tools while making exposure judgments using monitoring data. Logistic regression analysis indicated "years of exposure assessment experience" (p<0.05), "highest EHS degree" (p<0.05) and a participant's "data interpretation test score" (p<0.05) directly impacted qualitative exposure judgment accuracy. Logistic regression models of quantitative judgment accuracy showed positive correlation with "greater than 10 years of exposure assessment experience" (p<0.05), "highest EHS degree" (p<0.05), a participant's "data interpretation test score" (p<0.001), rule-of-thumb data interpretation training (p<0.001), and the number of sample data points available for a judgment (p<0.005). Analyzing judgments in subsets for participants with fewer or more than 10 years experience indicated additional correlations with Certified Industrial Hygienist and Certified Safety Professional certifications, total number of task exposure assessments, and career number of air surveys. The correlation of qualitative and quantitative exposure judgment accuracy with "greater than 10 years experience" supports similar research findings from other fields. The results of this study indicate that several determinants of experience, education and training, in addition to the availability of sampling data, significantly impact the accuracy of exposure assessments for the set of exposure tasks and agents used in this study. The findings also suggest methods for enhancing exposure judgment accuracy through statistical tools and specific training. Simulations were designed to evaluate the performance of several quantitative exposure assessments strategies for different exposure distributions. Bayesian tools are becoming popular and have been included in the simulations for this study along with simple comparison, point estimate and upper confidence limit strategies using minimum sample sizes less than 7 samples. The decision statistic selected for the simulations was the 95th percentile which defines acceptable exceedance fractions by 0.01%, 0.1%, 1%, and unacceptable defined by 10%, 20%, 30% and 50%. Bayesian strategies with using professional judgment were also included to illustrate the impact of an incorrect prior judgment. For acceptable exposure distributions, simple comparison and professional judgment integrated Bayesian strategies showed the highest probability for detecting an acceptable exposure. Bayesian strategies without professional judgment followed by upper confidence limit strategies were least likely to incorrectly define unacceptable exposure distributions as acceptable. Reviewing the different minimum sampling numbers for strategies indicate that Bayesian integrated methods most often arrive a correct decisions with less samples than other strategies. The results of this study can help design more effective and efficient exposure assessment and management strategies which will hopefully provide a transparent mechanism to strengthen accuracy and bias of exposure judgments.