Aflatoxin is a poisonous mold that has spread around the world, posing a threat to food security and the agricultural economy. A total of 4,5 million people are in danger of being exposed to aflatoxins on a long-term basis around the world. Acute toxicity is caused by consuming significant amounts of toxins in a short period of time, which can lead to death in the worst cases, whereas chronic toxicity is caused by consuming small quantities over a longer period of time, which can lead to low birth weight, immunosuppression, restricted growth in children, and liver cancer in the worst cases. The occurrence of aflatoxins in West Africa was recognized, studied, and investigated in this paper based on a literature review. The findings demonstrate that large levels of aflatoxins have been found in West African raw materials and food and the human body. Children under the age of five, pregnant women, and breastfeeding mothers are the most vulnerable to aflatoxins. Furthermore, the findings reveal that the majority of the population is unaware of aflatoxins and its health implications. Inadequate governmental systems, low societal development, lack of access to health care, a low educated population, climate variability and climate change, high levels of illiteracy, and a lack of laboratories are only a few of the many obstacles that the region has in limiting aflatoxins concentrations. Sorting procedures, the use of tarpaulins, and seminars have all helped raise awareness and knowledge and reduce contamination and consumption of aflatoxin-contaminated foods. This study argues that a multi-sectoral strategy is needed to promote food security and local education. Increased limitations and regulations and higher standards may be able to help limit aflatoxin contamination and exposure.

INTRODUCTION: The Charlestown Sprouts Community Garden, one of Bostonʼs largest community gardens, comprises 105 plots--all producing food--located in the historic neighborhood of Charlestown. It serves mainly minority and recent immigrant member households who rely on the land as a source of fresh produce. To ensure the safety of food production at the garden, the coordinators sought assistance from the Department of Environmental Health at the Boston University School of Public Health (BUSPH) to: 1. conduct a historical survey identifying past land uses, 2. characterize potential contaminant exposures to gardeners, and 3. furnish health-protective recommendations to minimize gardener hazard exposures. In the process of meeting these aims, broader dimensions of food production in the urban environment emerged from the literature: soil safety for urban agriculture, environmental justice, food security, determining “safe” levels of contaminants in urban soil, and the expansive policy implications that these issues engendered. For the work presented in this thesis project, the scope of interrelated topics were refined and lended contextual structure for a semi-quantitative characterization of human health risk from potential soil lead (Pb) exposures. This was accomplished by employing probabilistic modeling with the USEPA's Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK) (2010). Under specified assumptions of multimedia Pb exposures, the model predicts a theoretical young childʼs probability of his or her lead blood concentrationʼs (PbB) exceeding a PbB cutoff. For this analysis, the recently promulgated CDC reference value of 5 μg/dL was used as a cutoff in addition to the model default of 10 μg/dL. The IEUBK was also employed to approximate a range of soil Pb concentrations that could be considered “acceptable,” based on a health-protective approach; that is, to estimate a soil Pb concentration that would not significantly contribute to the exceedance of PbB > 5 μg/dL as a result of exposures to lead in soil. In this evaluation, an acceptable soil Pb concentration is defined as a mean soil Pb concentration that is determined by consideration of minimizing human health risk and maximizing practicability of the means to achieve the soil criterion—a level that could be reasonably achieved and be safe for urban agriculture. METHODS: Research for the historical survey included, but was not limited to, consulting historical fire insurance maps, archived municipal and county records, environmental databases, geographic information systems (GIS), and gathering accounts from local community members, historical societies, and multiple Boston city agencies to build a historical narrative about the garden land and the adjacent properties. For the IEUBK model runs, multimedia exposure parameter values from Boston environmental data (air, water, and soil) were used as inputs for the IEUBK modeling runs in the absence of suitable site-specific data. Comparison runs were executed with soil Pb concentration data from compost sourced from the City of Boston Department of Public Works Leaf and Yard Waste composting program and from Boston-area private compost facilities. RESULTS AND CONCLUSIONS: The garden was established at a site with a varied history of land uses from rail yard, to salt plant, to unknown activities. Community-member accounts, corroborated by photointerpretation data, suggest that the site was possibly an dumping grounds in the 1970ʼs-80ʼs. Based on the findings of the survey, it is likely that a number of potential contaminants exist at the garden, including lead, arsenic and/or polyaromatic hydrocarbons (PAHs). Based on visual inspection, point-source contamination of the soil is likely to be occurring at the garden, stemming from the treated rail ties that compose a majority of the garden plot constructions and of the plots inspected, the timbers appeared to be CCA-treated wood. The accumulation of site-specific knowledge gained through historical research, (GIS), and anecdotal evidence aided in determining what historical hazards were likely to pose a current risk to gardeners through gardening activities. The IEUBK model predicted a geometric mean blood value of 2.73 μg/dL with an associated risk of a young childʼs PbB exceeding 5 ug/dL as 9.9% using default parameter values. In comparison, to achieve a goal of less than 5% risk, the IEUBK modeling indicated that soil Pb would have to be less than 153 mg/kg. Under the guidance of BUSPH faculty, the findings and consequent recommendations, differing in remediation technique and resource-intensiveness, were summarized in a document for the garden steering committeeʼs development of imminent renovation plans.

Self-Efficacy (SE) has been explored extensively within the field of psychology. Despite a rich literature demonstrating its positive effect on various behavioral outcomes, including psychological treatment outcomes, little is known about the impact of SE on outcomes related to obsessive-compulsive disorder (OCD). To fill this critical gap in the literature, the aim of the present study was to determine whether increasing SE may improve engagement in exposure-based interventions for contamination fears. Nonclinical participants (N = 120) were randomly assigned to complete a contamination-related behavioral approach task (CR-BAT) immediately following either a SE-boosting exercise or a non-SE related control. Results demonstrated that there were no differences between conditions in contamination-related SE or approach behavior during the CRBAT, indicating that the manipulation was ineffective in boosting SE. Interestingly, however, participants in the SE-boosting condition reported lower levels of anxiety during certain phases of the CR-BAT than did those in the control condition, suggesting that the manipulation was effective in reducing subjective distress. Furthermore, SE was positively correlated with approach behavior during the CR-BAT, thus corroborating past research linking SE to behavioral outcomes. Future research, using more effective methods to manipulate SE, is required to examine the causality of this relationship.

The purpose of the present work was three-fold: (1) to determine the number of microorganisms found in root beer ready for consumer used, (2) to study the effects of various temperatures and durations of incubation on this microbial population, and (3) to characterize the predominant species of contaminating bacteria.

No description available.

Salmonella has been studied and researched for more than a hundred years and yet it remains a problem for human and animal health. The goal of this dissertation was to apply the systems thinking approach to Salmonella contamination and develop a System Dynamics (SD) simulation model for Salmonella contamination in the chill tank of a poultry processing plant. But first the appropriate carcass rinse sampling method that would not impact on the resulting Salmonella contamination status of the broiler carcass was studied. Kappa agreement analysis was used to evaluate three sampling methods. The adjacent rinse method was found to be the best method. In the absence of actual data, literature data was used to develop a literature-based SD simulation model of Salmonella contamination of broiler carcasses in the chill tank. The literature-based SD model is the first application of system dynamics simulation modeling in the poultry-processing field. The model was able to show and simulate the dynamic and non-linear interrelationships between parameters, namely pH, chlorine (Cl) level, water flow and turbidity. Actual data collection was done using a specially designed apparatus that recorded the time, temperature, pH, chlorine, water flow and turbidity in the chill tank as carcass rinse samples were collected. Linear regression analysis was used to identify the statistically significant models for relationships between the parameters in the chill tank. Finally, the data was analyzed using logistic regression to determine the association between the parameters in the chill tank and the occurrence of Salmonellaa in carcasses exiting the chill tank. These results were used to develop a data-based SD model. The data-based model was then validated using the validity tests proposed by various authors for SD simulation models and found to be a valid model. The developed model offers a fresh perspective to the problem of Salmonella contamination- to view it as a system of factors that are interrelated and have a feedback mechanism, rather than the traditional concept of linear causation. The developed model is a powerful cost efficient tool for testing interventions for reducing Salmonella contamination in the poultry processing plant.

Microwave scatterometers, which use radar backscatter measurements to infer the near-surface wind vector, are unique in their ability to monitor global wind vectors at high resolutions. However, scatterometer observations which are contaminated by land proximity or rain events produce wind estimates which have increased bias and variability, making them unreliable for many applications. Fortunately, the effects of these sources of contamination can be mitigated. Land contamination of backscatter measurements occurs when land partially fills the antenna illumination area. This reduces and masks the wind-induced backscatter signal. Land contamination is mitigated by quantifying the amount of contamination in a single observation using a metric referred to as the land contribution ratio (LCR). LCR levels which give rise to inadmissible levels of error in the wind estimates are determined and used to discard land-contaminated observations. Using this method results in contamination-free wind estimates which can be made as close to the coast as 5 km, an improvement of 25 km compared to previous methods. Rain contamination of scatterometer observations results from rain-induced scattering effects which modify the wind-induced backscatter. Rain backscatter effects are modeled phenomenologically to assess the impact of rain on the observed backscatter. Given the backscatter effects of wind and rain, there are three estimators: wind-only (WO), simultaneous wind and rain (SWR) and rain-only (RO), which have optimal performance in different wind and rain conditions. Rain contamination of wind estimates is mitigated using a new Bayes estimator selection (BES) technique which optimally selects WO, SWR, or RO estimates as they are most appropriate. BES is a novel adaptation of Bayes decision theory to operate on parameter estimates which may have different dimensions. The BES concept is extended to include prior selection and noise reduction techniques which generalizes BES to a wider variety of wind fields and further increase wind estimate accuracy. Overall, BES has wind estimation performance which surpasses that of either the WO or SWR wind estimates individually, and also provides a viable rain-impact flag.

Understanding the space environment and contamination concerns of a spacecraft is critical in designing a successful mission. The ability for a spacecraft to meet its science objectives relies on systems functioning as intended. A concern for maintain- ing performance while on orbit is molecular contamination. Silicones have previously been shown to form a silica layer on their surfaces when exposed to atomic oxygen. For silicone contamination, this translates to a silica film on the contaminated surface. Missions such as Long Duration Exposure Facility and Evaluation of Oxygen Interactions with Materials III have indicated that the silica film can trap deposits of carbon contamination to the surface during its formation. This phenomenon was explored in this research using RTV-S 691 silicone and Braycote 601EF for the carbon-based contaminant. The experiment involved contaminating an aluminum substrate in three different configurations; one for each contaminant individually on the substrate, and one with both contaminants. These samples were exposed to atomic oxygen for a period of 24 hours, then analyzed with Fourier transform infrared spectroscopy. The trends in infrared spectra for the different test cases were characterized for comparison. The trend for samples with a carbon-to-silicone contamination ratio of greater than ten to one showed peaks corresponding to those seen on the singularly contaminated samples. When the concentration of silicone was increased, the trend in spectral results showed peaks corresponding to Braycote before atomic oxygen exposure. At certain concentrations of RTV silicone to Braycote, the trends suggest Braycote is partially protected from atomic oxygen by a silica film. This indicates that silicone conversion to silica in atomic oxygen can trap contaminants to a surface.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

This research studied two predominantly rural counties in Virginia to understand whether residents have equal access to uncontaminated drinking water by socio-economic status. Statistical associations were developed with the total value of each residence based on county tax assessment data as the independent variable to explain levels of nitrate, the presence of bacteria (total coliform and Escherichia coli), and specific household well characteristics (well age, well depth, and treatment). Nearest neighbor analysis and chi-square tests based on land cover classifications were also conducted to evaluate the spatial distribution of contaminated and uncontaminated wells. Based on the results from the 336 samples analyzed in Louisa County, rural residents with private wells may have variable access to household drinking water free of bacteria; particularly if lower-value homes in the community tend to be older with more dated, shallower wells. This study also suggested that, in Louisa County, the presence of water treatment devices was also significantly related to total home value as an index of socio-economic status. Analysis of the 124 samples taken from household wells in Augusta County did not result in any significant associations among selected well characteristics, total home value, and water quality. Lower community participation in Augusta County as a result of a more expensive water quality testing fee may have contributed to the lack of hypothesized relationships in that county's case study. / Master of Science