Local exhaust (LE) ventilation is a ventilation technique where contaminated air is locally extracted close to the contaminant source usually with the purpose to reduce the exposure of workers to dust, fumes or vapour, which can be hazardous to their health. The performance of a LE installation depends however on many influential factors, and there is not yet an international standardized way to test LE constructions. The present study is the natural continuation of some previous studies at the University of Gävle that aimed at contributing to the establishment of such tests. The study entails full scale experimental measurements that include 3-D air velocity measurements and tracer gas tests in a controlled air turbulence environment generated through physical movements of a vertical, human-sized cylinder. These measurements were focused on human exposure, which was analysed by means of a seated human simulator for different configurations in which the exhaust flow rate, turbulence level, the exhaust hood arrangement and the measuring/injecting distance varied. The use of a sonic 3-D anemometer, that yielded both magnitude and direction of the air movement, proved very useful in analysing the generated air turbulence. As a measure of the LE performance, PNV value (Percentage of Negative Velocities) was used. This measure represents the percentage of time when the air flow at the measuring point in front of the exhaust hood is directed away from the nozzle, i.e. when the velocity component in the direction towards the exhaust hood opening is negative. Regarding the results obtained, in an otherwise undisturbed environment, measurement data showed that the natural convection from the human simulator sitting in front of the LE introduces some disturbances of the air flow in the suction region, proportional to the exhaust flow rate. However, when additional turbulence was generated through the controlled movements of the human-sized cylinder, thus creating a controlled turbulence setting, natural human convection leaded to a lower percentage of negative velocities (PNV) in comparison with the case in which human simulator was not present, especially for low exhaust air flow rates and when the exhaust hood was raised from the table. The tracer gas tests implied injection of a neutrally buoyant tracer gas through a perforated sphere placed in front of the exhaust hood. The amount of tracer gas that escaped from the suction flow was measured both in the room air and in the breathing zone. The first measurements yielded a sensitive method for measuring the capture efficiency (CE) of the exhaust hood. The CE is the percentage of injected tracer gas that is directly captured by the exhaust hood. This parameter showed that although the  convection flow generated by the human simulator leads to low PNV values, it seems that the tracer gas is not actually being captured, but trapped in that convection flow. As a consequence, PNV and CE get a strong correlation, which is even more intense when injection and capture point are closer together. Hence, PNV represents a good alternative to tracer gas measurements only if the relationship between the correlation of PNV and CE with respect to the distance from the injection to the capture point is known. Finally, measurements of tracer gas in the breathing zone showed random, short and high exposures when turbulence was generated and those exposures got worse by natural human convection.

This study aims to determine the concentrations of fluoride in UK tea products and their infusions. This is related to the uptake and distribution of fluoride within tea plants Camellia sinensis (L.). Human oral bioaccessibility of fluoride from the consumption of tea infusions was estimated, using an in vitro approach. The possible health significance from fluoride exposure is discussed. Fluoride in tea products and the distribution within the tea plant was determined using a method, involving alkali fused digestion with ion chromatography and a conductivity detector for the instrumentation. For the aqueous infusions and the supernatants in the bioaccessibility experiments, ion selective electrode with a voltmeter was adopted. Mean fluoride concentrations in tea products and their infusions varied significantly (p<0.001; n=3) and were related to the type of tea product and the retail cost. The higher priced teas, such as Darjeeling, Assam and Oolong, had lower fluoride concentrations. The lower priced supermarket Economy ranged teas were significantly higher (p<0.05) in fluoride and exhibited concentrations similar to Chinese Brick tea, which is prepared using mature tea leaves. The higher quality products are prepared by selecting the finest tips of tea (buds), whereas an Economy products use coarser harvesting techniques to include mature leaves in the product. Fluoride affinity and tolerance of C. sinensis was assessed by a series of fluoride dosing experiments, ranging from 0 to 200 mg. Following fluoride dosing, a rapid uptake and accumulation occurred throughout the tea plants, resulting in partial necrosis of random leaves. Despite the necrosis, the plants tolerated the fluoride and continued to increase in height, although at a significantly slower rate (p<0.05) compared to the control plants. Accumulation of fluoride was observed to be mostly in the mature leaves followed by younger buds, then the roots. This relates to the part of the plant used to produce the tea types, with mature leaves for Economy products and the buds for the finer teas. The in vitro bioaccessibility assessment of fluoride estimated that over 91.4% of fluoride from a tea infusion is available in the human gastric compartment, with 92.1% in the gastro-intestinal compartment. The addition of milk reduced fluoride absorption in the gastric and gastro-intestinal compartments to 73.8 and 83.1%, respectively, possibly reacting to form calcium fluoride. Despite the percentage bioaccessibility, the concentration of fluoride available for absorption in the human gut was dependent upon choice of tea product. Based on an adult male, the findings suggest that consuming a litre of Economy tea can fulfil or exceed (75 to 120%) the recommended dietary reference intake (DRI) of fluoride at 4 mg a day, but only partially fulfil (25 to 40%) when consuming a more expensive Pure blend such as Assam. With regards to health, tea consumption is a source of fluoride in the diet and is highly available for absorption in the human gut. Tea alone can fulfil an adult fluoride DRI, but is dependent upon choice of tea product. Excess fluoride in the diet can lead to detrimental health effects such as fluorosis of the teeth and skeletal fluorosis and consuming economy branded tea can lead to a higher exposure.

High levels of toxic heavy metals in the environment are a major concern and our knowledge about their adverse impacts and distribution patterns is improving. To mitigate human exposure for large regions, understanding the spatial distribution of metals in soil is key. Several types of models are available to predict the concentration levels, but they are often complex and data-intensive. The objective of this research is to explore the application of a simple method that produces geographically referenced predictions of surface soil concentrations of heavy metals. The approach uses publicly-available Canadian soil sample data, Geographic Information Science, statistical correlation and regression analyses. Geographically Weighted Regression (GWR) was used to investigate the spatial variability of the relationship between surface and the subsurface soil metal concentrations. Correlation analysis (Pearson’s) between the log of concentration levels of the two layers shows relationships of 0.51 for arsenic (As), and 0.23 for lead (Pb). Although the correlation results showed levels in the two layers are related, GWR analysis illustrates that the degree of this relation varies geographically. This study suggests that factors (natural and anthropogenic) other than the subsurface concentration itself are contributing to the concentration surface levels for all of the studied metals in this dataset. Based on the above findings, two linear regression models were developed to predict As and Pb levels in surface soil. Independent variables in the models were developed using geographic data on factors hypothesized to influence surface levels, an approach that has been extensively used for modelling air pollution and known as Land Use Regression (LUR). For the LUR analysis, the results show that industrial activities account for more than 70% of the variation of Pb concentrations in surface soil. Interestingly, the LUR model for As suggests that the bedrock geology and the total length of road at a location are the main factors. Both variables account for more than 40% of the variations of the As levels in surface soil in BC. The LUR results suggest that regional scale modeling of As and Pb surface soil concentrations can provide information about their spatial patterns that may be useful for understanding potential human exposure and the conduct of environmental epidemiological studies. / Graduate / 768 / 573 / 481 / steeved@uvic.ca

<p>An extensive use of chemicals in countless consumer products has resulted in human exposure to several persistent organic pollutants (POPs). Sufficient knowledge about their chemical composition properties and environmental faith is required, to be able to proper risk assess and regulate the substances. Significant data gaps exist regarding knowledge of actual exposure to humans and toxicological effect data.</p><p>The objective of this thesis was to add human exposure data of a few POPs from four case studies. The analytes discussed in this thesis are polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD).</p><p>Three European populations were studied. Milk was analysed from a group of women, who were accidentally exposed to high levels of 2,3,7,8-TetraCDD (TCDD) in Seveso, 1976. Still today, twice as high TCDD levels were recorded in the milk, compared to background concentrations. Serum was analysed from mothers and their infants from The Netherlands. Cord serum contained equal amounts of POPs as in mother’s blood, indicating non-hindered placenta transfer. Serum analysed from Swedish men and women with a high fish intake had elevated PCB and PCB metabolite (OH-PCB) levels. Additionally, butter was collected worldwide and shown to be a suitable matrix for dairy product survey of POPs.</p><p>The exposure levels in the four papers were compared to recently reported exposure levels in Europe. It is indicated in the thesis that the PCDDs/PCDFs and PCBs toxic equivalency (TEQ) levels are of concern, i.e. the ratio between threshold levels for adverse health effects and TEQ exposure levels is lower than requested margin of safety. Average levels of PBDE/HBCDD in the European population are estimated to be of no concern today, but for individuals with intakes at the 95th percentile are the current margins of safety small.</p>

Background: Arsenic (As) is a naturally-occurring element with known toxicant effects. The primary exposure pathway is through ingestion, but the overall contribution of food versus water and the impact of specific dietary nutrients on urinary As excretion is not well understood. Methods: Secondary analyses of laboratory results from food, water and urine samples, questionnaire and anthropometric data, and dietary records were performed on four study populations: the National Health Exposure Assessment Survey (NHEXAS)-Arizona, Arizona Border Survey (ABS), the Arizona sub-group of the Binational Arsenic Exposure Survey (BAsES), and the 2003-2004 National Health and Nutrition Examination Survey (NHANES). Dietary As intake was measured in duplicate food samples and/or modeled from dietary records for each population using the U.S. Total Diet Study (TDS) arsenic residue database and a published market basket survey. Urinary total As, As⁵, As³, monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) were analyzed, and sum of species As was calculated as the sum of As⁵, As³, MMA and DMA. Regression analyses modeled the relation between urinary As biomarkers (total, sum of species, MMA:sum of species, and DMA:MMA) and dietary As, adjusted for drinking and cooking water As intake, current smoking, sex, age, ethnicity, body mass index, and nutrient intake. Results: Modeled dietary As based on TDS mean As residue data greatly underestimated exposure as compared with measured As in duplicate diet samples and estimates based on other residue data. Dietary As was a significant predictor of urinary total As in all four populations, of sum of species As in both BAsES and NHANES, and of %MMA and DMA:MMA in NHANES. Dietary protein intake was associated with decreased sum of species As in both BAsES and NHANES, but dietary folate was not. Conclusions: Dietary As contributes a markedly greater proportion of total ingested As and is a better predictor of urinary As than water As intake in the U.S. Among subjects who did not consume seafood, total As exposure from food and water exceeded the provisional tolerable daily intake of 2.1 µg/kg body weight/day in 3-15% of these study populations. Increased protein intake may mitigate the effects of As.

An extensive use of chemicals in countless consumer products has resulted in human exposure to several persistent organic pollutants (POPs). Sufficient knowledge about their chemical composition properties and environmental faith is required, to be able to proper risk assess and regulate the substances. Significant data gaps exist regarding knowledge of actual exposure to humans and toxicological effect data. The objective of this thesis was to add human exposure data of a few POPs from four case studies. The analytes discussed in this thesis are polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD). Three European populations were studied. Milk was analysed from a group of women, who were accidentally exposed to high levels of 2,3,7,8-TetraCDD (TCDD) in Seveso, 1976. Still today, twice as high TCDD levels were recorded in the milk, compared to background concentrations. Serum was analysed from mothers and their infants from The Netherlands. Cord serum contained equal amounts of POPs as in mother’s blood, indicating non-hindered placenta transfer. Serum analysed from Swedish men and women with a high fish intake had elevated PCB and PCB metabolite (OH-PCB) levels. Additionally, butter was collected worldwide and shown to be a suitable matrix for dairy product survey of POPs. The exposure levels in the four papers were compared to recently reported exposure levels in Europe. It is indicated in the thesis that the PCDDs/PCDFs and PCBs toxic equivalency (TEQ) levels are of concern, i.e. the ratio between threshold levels for adverse health effects and TEQ exposure levels is lower than requested margin of safety. Average levels of PBDE/HBCDD in the European population are estimated to be of no concern today, but for individuals with intakes at the 95th percentile are the current margins of safety small.

>Magister Scientiae - MSc / Engineered nanomaterials derived from various bulk materials are being developed in ever larger quantities and with very diverse chemical compositions. The physical and chemical properties of the smaller nanoparticles are very different compared to their larger bulk chemicals. Titanium dioxide nanoparticles (TiO2NPs) are an example of such an engineered nanomaterial. Titanium dioxide nanoparticles are mainly used as a pigment in many applications such as glazes, enamels, plastics, pharmaceuticals, cosmetics, and it is widely used in sunscreens. Human exposure to TiO2NPs can occur both during manufacturing and use.

Phthalate esters (PEs) and organophosphate esters (OPEs) are common indoor pollutants frequently detected in environmental (dust, air), personal (hand wipes, diet) and human matrices (urine, serum etc.). In this thesis, mathematical models were used to establish links between intake and body burden for a comprehensive dataset based on a Norwegian study population. Also, the relative importance of different PE uptake pathways was assessed and discussed. Furthermore, the suitability of human nails as an alternative, non-invasive biomonitoring matrix for PEs was investigated. Additionally, information regarding alternative plasticizers to PEs was collected and presented extensively. Results showed that for PEs (paper II), daily intakes based on external exposure media agree with back-calculations using urinary metabolite concentrations, leading to the conclusion that human exposure for the general adult population is well understood and that the most important uptake routes were captured. Overall intake levels are comparable or lower than level presented in recent comprehensive studies and hazard quotients were well below 1 (low risk). As expected, diet was found to be the most important uptake route for all PEs. For lower molecular weight PEs, inhalation becomes a strong contributing pathway whereas for higher molecular weight PEs, dust ingestion was also important. Daily intake based on hand wipes was found to be much lower than the estimated total dermal intake based on air, dust and personal care products, questioning the relevance of hand wipes to represent total dermal exposure. Human nails were found to be unsuitable for replacing urine as a biomonitoring matrix for PEs as internal intake (from blood) cannot explain measured nail concentrations and uptake from air is too slow to reach observed concentrations within a realistic time frame (paper III). Hence, the kinetic links between intake and nail concentrations could not be established. Although exposure to traditional PEs is decreasing, use and body burden of some alternatives are increasing (paper I). Fortunately, most alternative plasticizers have favorable toxicological properties, resulting in low risk for humans. In contrast to PEs, OPEs still remain a group of poorly studied substances in terms of human exposure (paper IV). Due to lack of information regarding human metabolism, reliable links between intake and concentrations in serum and urine could not be established. Modelling results showed that concentrations in serum, and to some extent, urine, were underestimated for 2 compounds. It is likely that a combination of missing intake and suboptimal biomarkers were the cause for this under-prediction. Because of this, further studies regarding human metabolism should be performed for OPEs and potentially more specific biomarkers identified in the future. For PEs, there is a need for more comprehensive datasets to study exposure for high risk groups such as infants and children. Furthermore, dermal uptake remains poorly understood and the uptake of PEs into human nails should be studied in more detail to establish the kinetic links between exposure and body burden. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.</p>

Esse trabalho visa estudar a influência da vibração no desempenho de tarefas de pilotos de aeronaves. Para o seu desenvolvimento, foi montada uma bancada usando um assento de aeronave para avaliar a transmissibilidade da vibração vertical para os pilotos e verificar se níveis elevados de aceleração, como no caso de falha da turbina, podem prejudicar sua habilidade em desempenhar tarefas de leitura, escrita e digitação. Todos os experimentos foram realizados com sucesso, comprovando grande parte dos estudos anteriores sobre o assunto. Ainda são apresentadas comparações relacionando os mesmos níveis de aceleração usados no teste de transmissibilidade, com as normas ISO 2631-1 e ANSI S3.18 para avaliação da exposição humana à vibração de corpo inteiro, que são as mais apropriadas para a correlação com o mundo aeronáutico. / This work aims to study the influence of vibration in aircraft pilots task performance. For the study development, it was assembled a rig test using an aircraft pilot seat, in order to evaluate the transmissibility of vertical vibration to the pilots and to verify if high acceleration levels, as in the case of engine failure, are of significance to the pilots ability in performing tasks such as reading, writing and typing. All the experiments were accomplished successfully, confirming most of early studies about the subject. Comparisons are also presented, relating the same acceleration levels used in the transmissibility test with ISO 2631-1 and ANSI S3.18 standards for evaluation of human exposure to whole-body vibration which are the most appropriated for correlation with the aeronautical world.

Humans are continuously exposed to complex mixtures of anthropogenic chemicals. This thesis focus on human exposure to persistent organic pollutants (POPs). POPs ability to bioaccumulate and biomagnify together with the extensive historical use of POPs in e.g. agriculture and industry have resulted in detection of these compounds in humans and animals from all over the world. Adverse health effects caused by POPs are of particular concern for newborns and young individuals. The objective of this thesis is to assess human exposure to a selected set of POPs and their metabolites. More specifically, one aim of my thesis is to determine the exposure to polychlorinated biphenyls (PCBs) and in particular their methylsulfonyl and hydroxylated metabolites in humans from a “hot-spot” area of PCB contamination in eastern Slovakia. The maternal transfer of these chemicals is studied. Further, another specific aim is to determine occurrence, levels and, when possible, temporal trends of POPs in children and adults from three developing countries, Nicaragua, Guinea-Bissau and Bangladesh. High concentrations of PCBs and their metabolites are shown in men and women from Michalovce in eastern Slovakia. Placental transfer of methylsulfonyl-metabolites of PCBs and 4,4’-DDE was observed for the first time. Decreasing temporal trends of the majority of POPs are shown in serum from a cohort of policemen from Guinea-Bissau. In contrast, the levels of polybrominated diphenyl ethers (PBDEs) show an increasing time trend. Within five years, decreasing levels of POPs were also shown in children working and living at a waste disposal site in Nicaragua. Children working and living at waste disposal sites in Bangladesh have considerably lower levels of POPs compared to the children from Nicaragua except for 4,4’-DDT and 4,4’-DDE that are present at very high concentrations, indicating ongoing use of technical DDT. There are many studies on levels and trends of environmental pollutants from the developed industrial countries in the world, whereas data from developing countries is still scarce. This thesis contributes to partly fill this data gap since it includes assessments of POPs in children and adults from four countries on four continents. / At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Manuscript. Paper 6: Manuscript.