Background: Workers are daily exposed to diesel exhaust (DE) and DPM due to the continuous increase of diesel–powered vehicles in the underground mining environment. The National Institute for Occupational Safety and Health (NIOSH) recommends that DE be regarded as a “potential occupational carcinogen”. A great concern in the South African mining industry is that there is currently no existing occupational exposure limits (OEL) for DPM. Aim: To quantify the exposure of workers to DPM (that consists out of total carbon (TC): which is a combination of elemental carbon (EC) and organic carbon (OC)) in the ambient air of underground working environments. Also to compare different occupations exposure levels to an international standard (the Mine Safety and Health Administration’s (MSHA) OEL for TC) as South Africa has no proposed guideline or standard for occupational exposure to DPM and finally to determine whether or not occupations working at mines with different mining methods have different exposure levels to DPM. Methodology: Workers personal exposure to DPM was monitored using the NIOSH 5040 method. A DPM sampler that consisted of a cyclone, a pre–packed SKC filter cassette (37 mm) with impactor, tubing, label clips and a sampling pump was used. The flow rate was calibrated at 2.0 litres per minute (L/min) for the sampling of sub–micrometer particles. The personal sampler device was attached to the employee’s breathing zone for the duration of the work shift (normal eight–hour time–weighted average (TWA) standard). A high risk group (workers operating diesel–powered vehicles), a low risk group (workers working in the same mine, sharing the same supplied air, but not operating these vehicles) and a control group (workers working at a different mine with a different mining method) was monitored. The exposure levels were evaluated and compared with the specific OEL mentioned previously. Results: For the purpose of this study, TC exposure results were evaluated and not EC or OC. All the occupations within their specific exposure group was exposed to TC. When the control group’s exposures were compared with the high and low risk group exposures, a significant difference was recorded (p–value = 0.0001). However when the high and low risk exposures were compared with each other, no difference was recorded (p–value = 0.4405). When the results of the various groups were compared with the MSHA OEL all the occupations from the high and low risk group’s results were above the OEL, but only one occupation from the control group exceeded the OEL. Conclusion: It should be noted that all the occupations no matter the mining method / mine was exposed to TC. The high and low risk exposure groups was however much higher than the control group and a continues monitoring programme should be implemented for these exposure groups. Their results exceeded the OEL, where the control group had much lower exposure levels and only one occupation exceeded the OEL. Greater focus should be given to the mechanized mining occupations since diesel–powered vehicles are used to perform their core mining needs whereas at the conventional mine the use of these vehicles are limited. Recommendation: Depending on the different occupations sampled various engineering controls can be considered. Some include diesel oxidation catalysts (DOC), diesel particulate filters (DPF) and diesel disposable exhaust filters (DEF) or also known as disposable diesel exhaust filters (DDEF) which is very effective in removing DPM from the exhaust of dieselpowered equipment. Education and training are also critical components to the success of a diesel emission management programme and the last resort to be considered is the appropriate personal protective equipment (PPE). South Africa should consider the implementation of national standards in order to monitor the progress and success of the diesel emission management programme implemented. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2012.

Background: Workers are daily exposed to diesel exhaust (DE) and DPM due to the continuous increase of diesel–powered vehicles in the underground mining environment. The National Institute for Occupational Safety and Health (NIOSH) recommends that DE be regarded as a “potential occupational carcinogen”. A great concern in the South African mining industry is that there is currently no existing occupational exposure limits (OEL) for DPM. Aim: To quantify the exposure of workers to DPM (that consists out of total carbon (TC): which is a combination of elemental carbon (EC) and organic carbon (OC)) in the ambient air of underground working environments. Also to compare different occupations exposure levels to an international standard (the Mine Safety and Health Administration’s (MSHA) OEL for TC) as South Africa has no proposed guideline or standard for occupational exposure to DPM and finally to determine whether or not occupations working at mines with different mining methods have different exposure levels to DPM. Methodology: Workers personal exposure to DPM was monitored using the NIOSH 5040 method. A DPM sampler that consisted of a cyclone, a pre–packed SKC filter cassette (37 mm) with impactor, tubing, label clips and a sampling pump was used. The flow rate was calibrated at 2.0 litres per minute (L/min) for the sampling of sub–micrometer particles. The personal sampler device was attached to the employee’s breathing zone for the duration of the work shift (normal eight–hour time–weighted average (TWA) standard). A high risk group (workers operating diesel–powered vehicles), a low risk group (workers working in the same mine, sharing the same supplied air, but not operating these vehicles) and a control group (workers working at a different mine with a different mining method) was monitored. The exposure levels were evaluated and compared with the specific OEL mentioned previously. Results: For the purpose of this study, TC exposure results were evaluated and not EC or OC. All the occupations within their specific exposure group was exposed to TC. When the control group’s exposures were compared with the high and low risk group exposures, a significant difference was recorded (p–value = 0.0001). However when the high and low risk exposures were compared with each other, no difference was recorded (p–value = 0.4405). When the results of the various groups were compared with the MSHA OEL all the occupations from the high and low risk group’s results were above the OEL, but only one occupation from the control group exceeded the OEL. Conclusion: It should be noted that all the occupations no matter the mining method / mine was exposed to TC. The high and low risk exposure groups was however much higher than the control group and a continues monitoring programme should be implemented for these exposure groups. Their results exceeded the OEL, where the control group had much lower exposure levels and only one occupation exceeded the OEL. Greater focus should be given to the mechanized mining occupations since diesel–powered vehicles are used to perform their core mining needs whereas at the conventional mine the use of these vehicles are limited. Recommendation: Depending on the different occupations sampled various engineering controls can be considered. Some include diesel oxidation catalysts (DOC), diesel particulate filters (DPF) and diesel disposable exhaust filters (DEF) or also known as disposable diesel exhaust filters (DDEF) which is very effective in removing DPM from the exhaust of dieselpowered equipment. Education and training are also critical components to the success of a diesel emission management programme and the last resort to be considered is the appropriate personal protective equipment (PPE). South Africa should consider the implementation of national standards in order to monitor the progress and success of the diesel emission management programme implemented. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2012.

Immunological heterogeneity is the norm in most free-living vertebrate populations, creating a diverse and challenging landscape for pathogens to replicate and transmit. This dissertation work sought to determine sources of immunological heterogeneity, as well as the consequences of this heterogeneity on pathogen fitness and evolution. A major source of heterogeneity in free-living host populations is the degree of exposure to a pathogen, as well as a host's history of exposure to a pathogen, which can create variation in standing immunity. We sought to determine the role of exposure heterogeneity on host susceptibility and immunity to secondary infection, and the influence of this heterogeneity on pathogen fitness and virulence evolution in a wild bird-bacterium system. We first determined that exposure level has a significant effect on host susceptibility to infection, severity of disease and infection, as well as immunity produced to secondary infection. Subsequently, we tested whether exposure history, and the immunity formed from this previous exposure, altered the within-host fitness advantage to virulent pathogens. We determined that previous low-level repeat exposure, which wild hosts likely encounter while foraging, produces a within-host environment which greatly favors more virulent pathogens. While within-host processes are vital for understanding and interpreting the evolutionary pressures on a pathogen, the ultimate metric of pathogen fitness is transmission. We therefore tested whether exposure history altered the transmission potential of a host and whether prior host exposure selected for more virulent pathogens. The transmission potential of a host significantly decreased with previous exposure, and high levels of previous exposure selected for more virulent pathogens. While we anticipated selection to be strongest at low-levels of exposure based on our previous results, we found here that high doses of prior exposure resulted in the strongest transmission advantage to virulence. This study also provided insight into the nuanced nature of transmission, which our results indicate is determined both by the degree of within-host pathogen replication as well as host disease severity. Together, our findings underscore the importance of exposure level and exposure history in natural populations in determining susceptibility, immunity and pathogen virulence evolution. / Doctor of Philosophy / Infectious diseases disrupt and threaten all life on this planet. To better anticipate and understand why some diseases are more harmful than others, it is vital that we consider the natural variability that exists in animal populations. A major source of variation in populations that experience disease is exposure level to a pathogen, as well as the history of exposure to a pathogen, which can alter an individual’s protection against future exposures. We sought to determine the role of exposure level on the likelihood of an individual contracting an infection, their protection from future infections, and the influence this has on pathogen evolution in a wild bird-bacterium system. We determined that exposure level has a significant effect on the likelihood an individual has of becoming infected, how severe the infection became, as well as how protected they were from future infections. Subsequently, we tested whether exposure history, and the immunity formed from previous exposure, altered the ability of pathogen strains that cause different levels of harm to replicate. We determined that previous low-level exposure, which hosts likely encounter in the wild, creates a level of immunity that favors more harmful strains of the pathogen. While understanding what happens within a host is important, the ultimate metric for predicting whether more or less harmful types of pathogens will persist is the ability of each pathogen type to spread from one host to another. We therefore tested whether exposure history altered the spread potential of a host and whether previous exposure preferentially favored the spread of more harmful pathogens. The spread potential of a host was much lower if that host had previously been exposed to the pathogen, and high levels of previous exposure in hosts only allowed the more harmful pathogen types to spread. We also found that a host’s spread potential was the result of both how much pathogen they had in their body, as well as how inflamed their affected tissues were. Together, our results indicate that natural variation in prior exposure to pathogens, which is common in all animal populations, including humans, can favor more harmful pathogen types.

Made available in DSpace on 2015-05-14T13:16:23Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3324327 bytes, checksum: b85304a7fe276b9b7697e2cdf5a23471 (MD5) Previous issue date: 2013-12-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study aimed at verifying exposure levels for gasoline and ethanol vapors and their psychophysical, neurocognitive, and physiological consequences in a sample of Brazilian pump attendants. Gas chromatography and microclimate sensing were used to passive and active monitoring of environmental levels of vapors. The psychophysical evaluation comprised the chromatic tests Lanthony D15-d and Cambridge Color Test 2.0, the Contrast Sensitivity Function using vertical sinusoidal gratings and Metropsis at the frequencies 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 16.0 cpd, and eye-tracking at 250 Hz. Except by the D15-d test, all vision tests were performed with the dominant eye. The neurocognitive evaluation included the Trial Making Tests (A and B) and the Rey's Complex Figure Test. After applying exclusion criteria, the physiological evaluation was carried out in 16 attendants, who had a blood test to assess hepatic-biliary functions by the following markers: Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), Direct Bilirubin (DB), Total Bilirubin (TB), and Gamma-glutamyl transpeptidase (GAMMA GT). The screening phase also included a questionnaire of Psychological and Neurophysiological Symptoms (PNS), a sociodemographic questionnaire, the Ishihara and the Rasquin 'E' tests. Thirty-eight pump attendants (Exposed Group) were selected, all males, with mean age of 32.66 years (SD = 1.30) and average schooling of 9.68 years (SD = 0.34). Thirty-eight volunteers (Control Group) were selected, all males, with mean age of 30.0 years (SD = 1.54), average schooling of 9.84 years (SD = 0.34), without reporting exposure to solvents and considered healthy following the inclusion criteria. The groups did not differ in age (p = .224) or schooling (p = .52), and all participants had normal or corrected-to-normal visual acuity 20/20. The Mann-Whitney test showed significant differences between scores in the Index of Color Confusion of the D15-d (p < .01, with losses in the tritan axis 75%), the Area of ellipses (protan, deutran, and tritan, all at p < .05), the frequencies 5, 10, and 16 cpd (p < .01), the Trail Making A (p < .01) and B (p < .05), the copy and memory of the Rey's complex figure (both at p < .01), and the number of saccades and trajectory time in the visual labyrinth (both at p < .01) as measure by the eye-tracker. The physiological evaluation showed changes in the values of DB (100 % of the pump attendants) and TB (62,5 %). Two attendants had combined changes in hepatic enzymes and biliburin. The Spearman correlation showed a significant association between the time of service and the areas protan (ρ = .46, p < .01) and deutan (ρ = .64, p < .01), the spatial frequency 5 cpd (ρ = .36, p < .05), and the Trail Making A (ρ = .40, p < .05) and B (ρ = .37, p < .05). The weight showed a tendency to attenuate the visual deficits, having a negative correlation with the area deutan (ρ = - .45, p < .01) and a positive one with contrast sensitivity at 0.20 cpd (ρ = .37, p < .05). Correlations were also found between DB and the time to perform the eye-tracker task (ρ = .58, p < .05) and the GGT and complaints of psychoneurovegetative instability (ρ = .57, p < .05). The Kruskal Wallis, and Mann-Whitney as a post-hoc test with Bonferroni's correction, showed that from 8 years of exposure there are consequences to color vision (Protan and Deutan) and for neurocognitive processes related to attention (Trail Making). The questionnaire PNS showed that 52.6% of pump attendants had symptoms of neuropsychological aggressions. Furthermore, there was a convergence between memory and attention complaints, with lower scores in the memory for the Rey's complex figure (ρ = - .34, p < .05). This study brings additional and new evidences for the consequences on color vision and contrast sensitivity, shows a potential occupational etiology in hepatic-biliary changes, presents neurocognitive xviii deficits in Brazilian pump attendants, and concludes that such deficits are correlated with chronic exposure (significant from 8 years of service) with a level of exposure to gasoline and ethanol below the Brazilian tolerance limit, but within an intervention level to gasoline vapor (168 and 153,40 ppm > 150 ppm) according to the Brazilian Standards for Work Health and Safety. / O objetivo deste estudo foi determinar os níveis de exposição aos vapores da gasolina e do etanol e verificar as consequências psicofísicas, neurocognitivas e fisiológicas em uma amostra de frentistas brasileiros. Para avaliar o nível de exposição ambiental foram realizados monitoramentos passivos e ativos de vapor com cromatografia gasosa e sensoriamento microclimático. A avaliação psicofísica foi realizada com os testes cromáticos de Lanthony D15-d e o Cambridge Color Teste 2,0; com a Função de Sensibilidade ao Contraste utilizando grades senoidais verticais e o Metropsis nas frequências 0,2; 0,5; 1,0; 2,0; 5,0; 10,0 e 16,0 cpg e com o rastreamento ocular utilizando um eyetracker 250 Hz. Todos os testes de visão, exceto o D15-d, foram realizados monocularmente com o olho dominante. A avaliação neurocognitiva ocorreu com os testes Trail Making A, B e com a Figura Complexa de Rey. A avaliação fisiológica, após utilização de parâmetros de exclusão, foi realizada pela análise de sangue de 16 frentistas verificando funções hepatotóxicas pelos marcadores Alanina Aminotransferase (ALT), Aspartato Aminotransferase (AST), Bilirrubina Direta (BD), Bilirrubina Total (BT) e Gamaglutamiltraspeptidase (GGT). Utilizou-se ainda o questionário de sintomas Psicológicos e Neurofisiológicos (PNF) além de um questionário sóciodemográfico e os testes de Ishihara e o ―E‖ de Rasquin na triagem. Essa etapa selecionou 38 frentistas do sexo masculino (Grupo Exposto), com idade média de 32,66 anos (DP = 1,30), grau de escolaridade média igual a 9,68 anos de estudo (DP = 0,34) e 38 voluntários (Grupo Controle) também do sexo masculino, sem histórico de exposição a solventes, considerados saudáveis pelos parâmetros de exclusão, com idade média de 31,00 anos (DP = 1,54) e grau de escolaridade médio de 9,84 anos de estudo (DP = 0,34). Não existiu diferença significativa entre a idade (p = 0,224) e o grau de escolaridade (p = 0,52) dos grupos que apresentaram ainda acuidade visual de 20/20 ou corrigida. Pelo teste de Mann-Whitney foram encontradas diferenças significativas entre os escores para: o Índice de Confusão de Cores do teste D15-d (p < 0,01, prevalecendo perdas no eixo tritan 75%), as Áreas das elipses (protan, deutan e tritan, ambos p < 0,05), as frequências 5 cpg, 10 cpg e 16 cpg (ambos p < 0,01), o teste Trail Making A (p < 0,01) e B (p < 0,05), a cópia e a memória da Figura complexa de Rey (ambas p < 0,01) e o número de sacadas e tempo de percurso do labirinto no eyetracker (ambos p < 0,01). A avaliação biológica demonstrou principalmente alterações nos valores da BD (100 % dos frentistas) e BT (62,5 %). Dois frentistas tiveram alterações combinadas de enzimas hepáticas e bilirrubinas. A correlação de Spearman demonstrou a influência do tempo de serviço no acréscimo das áreas protan (ρ = 0,46; p < 0,01) e deutan (ρ = 0,64; p < 0,01), além de correlações com a frequência de 5 cpg (ρ = 0,36; p < 0,05) e com os testes Trail Making A (ρ = 0,40; p < 0,05) e B (ρ = 0,37; p < 0,05). O peso apresentou a tendência de atenuar os déficits nos testes de visão, correlacionando negativamente com a área deutan (ρ = - 0,45; p < 0,01) e positivamente com a sensibilidade ao contraste na frequência 0,20 cpg (ρ = 0,37; p < 0,05). Existiram ainda correlações entre a BD e o tempo para realizar a prova no eyetracker (ρ = 0,58; p < 0,05) e entre o GGT e as queixas de instabilidade psiconeurovegetativa (ρ = 0,57; p < 0,05). Os testes Kruskal Wallis, e Mann- Whitney como post hoc com correção Bonferroni, demonstraram que a partir de 8 anos de exposição existem consequências para a visão de cores (Protan e Deutan) e para processos neurocognitivos relacionados a atenção (Trail Making A). O questionário PNF apontou que 52,60 % dos frentistas possuem sintomas de agressões neuropsicológicas. Além disso, existiram convergências entre as queixas de falta de memória e concentração, com menores pontuações da memória na Figura Complexa de Rey (ρ = - 0,34; p < 0,05). Este estudo confirma e avança nas descobertas de consequências na visão de cores e sensibilidade ao contraste, aponta uma possível etiologia ocupacional nas alterações hepatotóxicas, apresenta as deficiências neurocognitivas nos frentistas brasileiros e conclui que essas deficiências e as da visão de cores estão correlacionadas a uma exposição crônica (significativa aos 8 anos de serviço) com um nível de exposição a gasolina e ao álcool etílico abaixo do Limite de Tolerância brasileiro, mas a um nível de intervenção para o vapor de gasolina (168,00 e 153,40 ppm > 150 ppm) conforme as Normas de Saúde e Segurança do Trabalho brasileiras.

La nourriture traditionnelle compose une part essentielle de la culture Inuit. Néanmoins, la contamination de cette nourriture par les organochlorés et les métaux lourds fait l’objet d’une attention toute particulière, car elle excède dans certains cas les recommandations canadiennes. Le but de ce travail est, d’une part de mettre à jour les estimés d’exposition au chlordane, au BPC, au toxaphène et au mercure, et d’autre part d’en explorer certaines sources de variation. Pour ce faire, de nouvelles données sur la concentration de ces contaminants parmi les plus importants aliments traditionnels ont été combinées aux relevés alimentaires assemblés dans l’Arctique canadien en 1998 et 1999, la quantité et le type de nourriture traditionnelle consommés étant supposés ne pas avoir changé. D’après l’ensemble des nouveaux estimés obtenus, les changements dans la banque de données sur les contaminants affectent plus les extrémités des distributions que les mesures de tendance centrale. Les estimés d’apports en organochlorés peuvent être considérés comme toujours actuels étant donné que les cinq types d’aliments pour lesquels il y a des nouvelles données disponibles représentent la majorité de l’exposition totale. En ce qui concerne le mercure, toutefois, des données additionnelles sont nécessaires à propos du caribou, du narval, du muktuk du béluga et de la truite de lac pour générer des niveaux d’exposition plus exacts. Les sources de variations de ces estimés d’exposition ont été explorées en évaluant les coefficients de variation propres aux apports alimentaires et ceux propres aux concentrations de contaminants dans les aliments traditionnels. Il s’avère que la variation attribuable aux méthodes de collecte de données alimentaires est plus élevée que celle attribuable à la mesure des contaminants dans les banques de données. De nouvelles méthodes pour mesurer les niveaux de consommation d’aliments traditionnels devraient être développées. / Traditional food is a part of Inuit culture. Nevertheless, contamination of this food by organochlorines and heavy metals is the subject of constant attention since it’s exceeding Canadians guidelines in some cases. The purpose of this work is to do an update of the exposure estimates for chlordane, PCB, toxaphene and mercury and to explore sources of variation. To do so, new data on concentration of contaminants in traditional food have been combined to dietary recalls collected in the Canadian arctic in 1998 and 1999 assuming that the quantity and the type of traditional food consumed didn’t change. According to the new estimates, changes in the contaminant database affected more the extremes of the distributions rather than the measures of central tendency. The estimates of organochlorines intakes can be considered updated since the five types of food for which data are available represent the majority of total exposure. For mercury, additional data are necessary for caribou, narwhal, beluga muktuk and lake trout to generate more exact estimates of exposure. The sources of variation of the exposure estimates have been explored by evaluating the coefficients of variation related to the measure of the dietary intake and those related to the contaminant concentrations in traditional food. The variation attributable to the methods of collecting food intake data is higher than the variability attributable to the contaminant database. New methods to measure the levels of traditional food consumption should be developed.

La nourriture traditionnelle compose une part essentielle de la culture Inuit. Néanmoins, la contamination de cette nourriture par les organochlorés et les métaux lourds fait l’objet d’une attention toute particulière, car elle excède dans certains cas les recommandations canadiennes. Le but de ce travail est, d’une part de mettre à jour les estimés d’exposition au chlordane, au BPC, au toxaphène et au mercure, et d’autre part d’en explorer certaines sources de variation. Pour ce faire, de nouvelles données sur la concentration de ces contaminants parmi les plus importants aliments traditionnels ont été combinées aux relevés alimentaires assemblés dans l’Arctique canadien en 1998 et 1999, la quantité et le type de nourriture traditionnelle consommés étant supposés ne pas avoir changé. D’après l’ensemble des nouveaux estimés obtenus, les changements dans la banque de données sur les contaminants affectent plus les extrémités des distributions que les mesures de tendance centrale. Les estimés d’apports en organochlorés peuvent être considérés comme toujours actuels étant donné que les cinq types d’aliments pour lesquels il y a des nouvelles données disponibles représentent la majorité de l’exposition totale. En ce qui concerne le mercure, toutefois, des données additionnelles sont nécessaires à propos du caribou, du narval, du muktuk du béluga et de la truite de lac pour générer des niveaux d’exposition plus exacts. Les sources de variations de ces estimés d’exposition ont été explorées en évaluant les coefficients de variation propres aux apports alimentaires et ceux propres aux concentrations de contaminants dans les aliments traditionnels. Il s’avère que la variation attribuable aux méthodes de collecte de données alimentaires est plus élevée que celle attribuable à la mesure des contaminants dans les banques de données. De nouvelles méthodes pour mesurer les niveaux de consommation d’aliments traditionnels devraient être développées. / Traditional food is a part of Inuit culture. Nevertheless, contamination of this food by organochlorines and heavy metals is the subject of constant attention since it’s exceeding Canadians guidelines in some cases. The purpose of this work is to do an update of the exposure estimates for chlordane, PCB, toxaphene and mercury and to explore sources of variation. To do so, new data on concentration of contaminants in traditional food have been combined to dietary recalls collected in the Canadian arctic in 1998 and 1999 assuming that the quantity and the type of traditional food consumed didn’t change. According to the new estimates, changes in the contaminant database affected more the extremes of the distributions rather than the measures of central tendency. The estimates of organochlorines intakes can be considered updated since the five types of food for which data are available represent the majority of total exposure. For mercury, additional data are necessary for caribou, narwhal, beluga muktuk and lake trout to generate more exact estimates of exposure. The sources of variation of the exposure estimates have been explored by evaluating the coefficients of variation related to the measure of the dietary intake and those related to the contaminant concentrations in traditional food. The variation attributable to the methods of collecting food intake data is higher than the variability attributable to the contaminant database. New methods to measure the levels of traditional food consumption should be developed.