This research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science in Dentistry. School of Oral Health Science, Faculty of Health Sciences, University of the Witwatersrand, South Africa Johannesburg, 2017 / Purpose: Resin restorative materials have improved over the years. A major obstacle to the acquisition of acceptable bond strength of bonding agents is the presence of contaminated dentine cavity preparations. The purpose of this study was to investigate the effects of oral contaminants such as blood, saliva and a disinfectant contamination on the shear bond strength of a nanocomposite on a self-etching adhesive system. Materials and Methods: Thirty-six caries free premolar teeth were extracted and placed in a disinfectant solution containing 0.5 % Chloramine T solution, and then randomly distributed into four groups. Each tooth was then placed into a stainless steel ring supported by clear self-curing acrylic. They were thereafter immersed into a saline solution of 37 ̊C - 37.5 ̊C in an incubator for 24 hours. The enamel surfaces of the premolars were then ground with a Pro-trim 1725 Hertz grinder using 600 grit silicon carbide fine grinding paper to expose the dentine surface of each tooth. The sample was then re-immersed in the saline solution and incubated at 37°C - 37.5°C. The teeth were then arranged into the four groups: Group 1 (control group); Group 2 (human blood contamination at 5 seconds); Group 3 (human saliva contamination at 5 seconds) and Group 4 (chlorine dioxide contamination at 5 seconds). A self-etching adhesive bonding system (Scotchbond universal™) and Filtek supreme XTE composite was applied to the exposed dentine surface. Samples were randomised and then sheared using an Instron testing machine to determine their bond strengths. The fractured components of each sample were measured, compared and further examined under a stereo microscope to determine the modes of failure. The data were analysed using a one-way analysis of variance (ANOVA) and the level of significance was set at a p-value of less than 0.05. Results: A significant difference was found in the shear bond strength between the control (group 1) and the blood contaminated group (group 2) (p-value of 0.00064). The chlorine dioxide group (group 4) that had no effect on shear bond strength to dentine (p-value of 0.55). Adhesive failures (between bonding agent and dentine) were predominant in group 2 and to a lesser extent in group 3. Most group 4 samples had cohesive fractures (within the dentine). Conclusion: The bond strength to dentine using a self-etching adhesive was reduced when contaminated with blood. Group 2 samples (blood) caused significantly greater bonding failure as compared to all the other groups. Chlorine dioxide solution is a powerful disinfectant and does not affect the bonding to dentine. The null hypothesis statement, which stated that there was no difference in the shear strength between any of the conditions, was thus rejected. Further studies on the application of chlorine dioxide as a disinfectant on cavity preparations need to be considered given the surprising positive results of chlorine dioxide group. / MT2018

Ce travail de recherche porte sur l'étude de trois familles de contaminants organiques hydrophobes persistants : hydrocarbures aromatiques polycycliques (HAP), polychlorobiphényles (PCB) et pesticides organochlorés (OCP) dans les sédiments d'une lagune méditerranéenne : l'étang de Thau. Les niveaux et les distributions géographiques ont été déterminés pour chaque famille de contaminants étudiés. De même, leurs stocks et leurs flux ont été estimés dans le sédiment de surface. L'étude des carottes sédimentaires a permis de reconstituer l'historique de la contamination des sédiments de l'étang de Thau. Cet historique s'avère représentatif de l'évolution de la contamination au niveau national et concorde avec les tendances européennes et mondiales. L'étude des carottes sédimentaires a également fourni des renseignements sur la dynamique de la contamination des sédiments dans l'étang de Thau. Les grandes tendances temporelles, les inventaires et les flux ont été quantifiés pour les trois familles des contaminants étudiés. Enfin, une étude expérimentale plus restreinte sur la disponibilité des contaminants associés aux sédiments de l'étang a également été réalisée. Ce travail a permis d'aborder la disponibilité des contaminants sur différents niveaux d'une carotte sédimentaire en fonction de la nature : l'origine et l'âge de la matière organique et des propriétés physico-chimiques des contaminants. L'approche expérimentale de cette étude a été basée sur l'utilisation d'un échantillonneur passif. Les premiers résultats ouvrent des perspectives de travail visant à une meilleure compréhension de la disponibilité des contaminants sédimentaires.

The extensive use of pharmaceuticals and their poor removal by wastewater treatment plants has led to the emergence of pharmaceutical compounds as global aquatic contaminants. Progestins, the synthetic analogues to progesterone (P4), are receiving increasing attention as contaminants and have been shown to impair reproduction in fish and amphibians at low ng L-1 concentrations. Certain progestins have androgenic properties and are several orders of magnitude more potent in terms of reproductive impairment in fish than non-androgenic progestins. To characterize the androgenic effects of progestins in fish, adult three-spined sticklebacks (Gasterosteus aculeatus) and zebrafish (Danio rerio) larvae were exposed to progestins via the ambient water. In female sticklebacks, the androgenic progestins levonorgestrel (LNG) and norethindrone (NET) induced production of the androgenic biomarker protein spiggin and reduced production of the egg yolk protein vitellogenin. Comparison with well-known environmental androgens showed that LNG and NET, with regard to spiggin induction and vitellogenin induction, are among the most potent environmental androgens known. In male sticklebacks, LNG inhibited the post-breeding regression of secondary sex characters and spiggin production, as well as the resumption of spermatogenesis, functionally inhibiting the natural transition from breeding into non-breeding condition. Exposure of zebrafish larvae to LNG caused all fish to develop into males, whose sexual development was also significantly accelerated. P4 had no effect on the sex ratio, while slightly accelerating sexual development at high concentrations. Suppression of vitellogenesis in females, disruption of the male reproductive cycle, male-biased sex ratios and precious male puberty could all entail severe fitness costs and severely affect fish populations. Most of the effects of androgenic progestins in this thesis occurred at levels within the range of reported environmental levels, and may therefore occur in progestin-contaminated waters. In conclusion, the present results establish LNG and NET as highly potent androgenic pollutants of environmental concern, and provide strong support to the contention that the reproductive impairment in fish caused by progestins is chiefly mediated by their androgenic properties.

<p>It is estimated that 22 000 contaminated areas exist in Sweden today. In order to classify the risk of contaminant migration from these areas and to prioritize which of these contaminated areas should first be treated, the Swedish Environmental Protection Agency (EPA) has designed a method, for the investigation of contaminated areas (MIFO). One of these contaminated areas is the landfill Gräsötippen outside Köping. The landfill has been used by both Yara AB and the Köping municipality between the years 1945 and 1975, and both industrial and household waste have been deposited there. The aim of this report is to survey which contaminants that can be found in the soil and water in the landfill Gräsötippen and to evaluate the migration of these contaminants. With help of this information, the landfill will then be risk classified according to MIFO. The goal is that this report will provide a basis for future studies and remedial measures at the landfill.</p><p>To get a picture of what has been deposited at the landfill Gräsötippen, employees and former employees at Yara and others with connection to the landfill have been interviewed. Piezometers have been installed in and around the landfill so as to provide information on groundwater levels and movement, and for the collection of groundwater samples. Soils samples were collected as well. The water and soil samples were analyzed with regard to metals, organic compounds and nutrients. Furthermore, groundwater flow has been modeled using VS2DI, in order to get a picture of the groundwater’s flow direction and velocity under the landfill.</p><p>In the water samples, only lead was detected with levels over the Maximum Contaminant Level (MCL) from the EPA. Relatively high levels of nutrients were also detected. In the soil, carcinogenic PAH, PCB, aliphatic hydrocarbons, aromatic hydrocarbons, arsenic, lead, cadmium, mercury and zinc were detected over the EPA MCL. The landfill Gräsötippen has a good location in an area with deep clay, which prevents rapid spreading of contaminants. No high levels of contaminants are leaching out today. The spreading of the contaminants is minor; most of the contaminants are fixed in the soil and do not spread to the surroundings. The water flow’s primary direction from the landfill is south but there are also flows to the west and east. Today, there are a number of proposals with regard to decreasing the risk for future contaminant dispersal from the landfill and to keep control of the water that is used in the area. A few of these proposals are to finally cover the landfill, to analyze the grass and plants in the enclosed pasture on the landfill, and to continuously analyze the water in the installed piezometers and drinking water wells on and around the landfill. The landfill Gräsötippen is classified to risk class 3, moderate risk, according to MIFO.</p> / <p>Det uppskattas idag finnas 22 000 förorenade områden i Sverige. För att kunna riskklassa dessa förorenade områden och prioritera vilka som först bör efterbehandlas har Naturvårdsverket utarbetat en Metodik för Inventering av Förorenade Områden (MIFO). Gräsötippen utanför Köping är ett av dessa förorenade områden. Deponin har använts av både Yara AB och Köpings kommun mellan åren 1945-1975 och fungerat som deponi för både industri- och hushållsavfall. Syftet med denna rapport är att kartlägga vilka föroreningar som finns i mark och vatten i Gräsötippen och tolka föroreningarnas spridning. Utifrån den informationen ska deponin sedan riskklassas enligt MIFO. Målet är att rapporten ska kunna fungera som underlag för framtida åtgärdsplaner för Gräsötippen.</p><p>För att få en bild över vad som har deponerats på Gräsötippen har anställda och före detta anställda vid Yara samt andra som har haft anknytning till Gräsötippen intervjuats. Grundvattenrör har installerats i och runtom deponin för att det skulle kunna tolkas hur grundvattnet rör sig under deponin och för att det skulle kunna tas prover på grundvattnet och jorden. De vatten- och jordprover som togs, analyserades med avseende på metaller, organiska föreningar och närsalter. Dessutom har en modellering utförts i VS2DI för att få en bild över grundvattnets flödesriktning och hastighet under deponin.</p><p>I vattenproven detekterades endast bly över Naturvårdsverkets riktvärde samt relativt höga halter av närsalter. I jorden detekterades cancerogena PAHer, PCB, alifater, aromater, arsenik, bly, kadmium, kvicksilver och zink över Naturvårdsverkets riktvärden. Gräsötippen är bra placerad i ett område med tjock lera som förhindrar snabb spridning och idag lakas inga höga halter av föroreningar ut. Spridningen av föroreningar är liten, istället ligger de flesta föroreningarna fast i marken och sprids därmed inte till omgivningen. Vattenflödets huvudriktning från deponin är söderut, men det sker även flöden åt både väster och öster. Det finns i dagens läge en del förslag på åtgärder som bör utföras på Gräsötippen för att minska risken för framtida spridning och upprätthålla kontroll på det vatten som används i närområdet. Några av dessa åtgärder är att sluttäcka deponin, att analysera gräs och växter i hagen på deponin samt att kontinuerligt analysera vattnet i grundvattenrören och brunnarna på och runt Gräsötippen. Vid riskklassningen av Gräsötippen enligt MIFO, klassas den till riskklass 3, måttlig risk.</p>

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During military operations, a small fraction of propellant mass is not consumed during firing and is deposited onto the ground surface. Soluble propellant constituents can be released from particulate residues into the environment. The release of uncombusted propellant residues and transformation products results in soil, surface water, and ultimately groundwater contamination. It is important to study the potential for off-site migration of munitions and to provide qualitative data that helps better understand transit of these propellant constituents. Propellant constituents of interest for this study were nitroglycerine (NG), 2,4-dinitrotoluine (2,4-DNT), 2,6-dinitrotoluine (2,6-DNT), and nitroguanidine (NQ). The goal of this work is to determine fate and transport parameters, partition/distribution coefficients and transformation rates for these compounds in three soils that represent a range of geographic locations and soil properties. This supports a companion study that looks at dissolution of constituents from fired and unfired solid propellant formulations and their transport in soil.

No description available.

Student Number : 0316126G - MSc dissertation - School of Animal, Plant and Environmental Sciences - Faculty of Science / I investigated whether inorganic contaminants associated with gold mining waste discharges in the Free State Province, South Africa, were accumulated by a threatened species of lizard, Cordylus giganteus; if the route of exposure could be dietary, and whether accumulation of contaminants could be associated with potential physiological costs. I compared elemental concentrations in tissue and blood samples between populations of this species, from four sites around the province. Inorganic contaminants were known to be elevated in soils, water, sediments and vegetation of the first mining site, and to a lesser extent at the second mining site. The third site was not known to be contaminated by mining discharges, but was selected because of its potential to be contaminated by wind-blown contaminants. This site was also heavily overgrazed. The fourth site was both uncontaminated by mining and relatively undisturbed. Lizards from the most contaminated site had significantly higher blood concentrations of Li, Na, Al, S, Ca, P, Si, Cr, Mn, Fe, Ni, W and Bi when compared with all the other sites investigated. Based upon a comparison of elemental concentrations in selected lizard prey items found at these sites (Coleoptera, Tenebrionidae) I did not find conclusive evidence for a dietary route of exposure to contaminants. I tested for significant differences in body condition among populations. Lizards from the heavily grazed site were in similar condition to lizards from the most contaminated site, and all these lizards were in significantly poorer condition than lizards from the undisturbed site. The adult sex ratio of the population inhabiting the most contaminated site also deviated significantly from an expected 1:1 ratio in favour of females. The reason for this deviation is not understood, but may be a consequence of sexes being differentially affected by inorganic contaminants. My research demonstrates that the disposal of gold and uranium mine waste has resulted in the accumulation of contaminants by a representative resident vertebrate, and that this accumulation is potentially associated with poorer body condition which might affect fitness. It highlights the potential threat of mining-waste discharges to lizards, shows the need for site remediation measures, and also highlights the need for further investigation into the potential effects of environmental contaminants from gold and uranium mine waste on exposed vertebrates in South Africa.

Très appréciés des consommateurs du fait de leur qualité nutritionnelle, les produits de la mer jouent un rôle important dans l'alimentation humaine. Toutefois, la confiance du consommateur vis-à-vis de leur qualité est affectée par les riques associés à une exposition aux contaminants chimiques et à la fraîcheur des produits. Si le premier aspect résulte de la pollution des eaux marines sous l'effet d'une forte anthropisation des littoraux, le second est lié à la haute périssabilité de ces produits. Évaluer les niveaux de contamination chimique et la qualité-fraîcheur des produits de la mer est plus qu'un besoin : c'est aujourd'hui une nécéssité. C'est dans ce contexte que les travaux de cette thèse ont été menés. Deux objectifs principaux ont été visés dans la présente étude. Le premier objectif de ce travail était de faire une évaluation spatiale et saisonnière des niveaux de contamination par les polluants métalliques et organiques (HAPs et PCBs) des zones côtières du Sénégal en s'intéressant aux teneurs en contaminants dans les organismes marins. Nous avons étudié 7 espèces marines représentatives des différents maillons de la chaîne trophique (une macroalgue verte, un mollusque bivalve, un crustacé et 4 espèces de poisson) prélevées le long du littoral au niveau de 5 sites présentant des degrés d'anthropisation différents. Les résultats de cette étude montrent que les teneurs en contaminants chimiques des organismes marins sont variables selon les espèces et soulignent ainsi la nécéssité de l'approche multi-espèces pour l'étude de la contamination chimique du milieu. Des variations inter-sites de la teneur en contaminants chimiques dans les organismes ont été mis en évidence. Les sites les plus anthropisés comme Soubédioune et Rusfisque sont ceux qui présentent les teneurs les plus élevées. Les niveaux de contamination métalliques et organiques dans les organismes marins du littoral sénégalais sont inférieurs ou du même ordre de grandeur que ceux mesurés dans d'autres régions d'Afrique de l'Ouest ou dans d'autres régions du monde. L'évaluation des risques associés à l'ingestion des produits de la mer analysés montre que les teneurs en contaminants chimiques sont faibles et inférieures aux limites maximales admissibles pour la consommation humaine (norme EU). Seuls les sites de Rufisque et Soumbédioune présentent quelques dépassements chez certaines espèces (moules, sardinelles). Le deuxième objectif de cette étude était de développer des méthodes permettant d'évaluer la fraîcheur des filets de poisson et de différencier des filets frais des filets décongelés. Les méthodes retenues sont basées sur la mesure de l'augmentation de la perméabilité cellulaire du muscle de poisson. La conservation des filets de poisson à 4°C va conduire à une perméabilisation des cellules dans le temps qui peut être apréhendée par la mesure de la libération d'enzymes intracytoplasmiques ou par l'augmentation de la perméabilité des cellules à des colorants fluorescents. La mesure de l'activité LDH est intéressante à double titre : elle va permettre d'une part de mesure le niveau de lyse cellulaire, donc le niveau d'altération, des filets de poisson dans le temps. Elle va permettre d'autre part grâce à sa sensibilité à la congélation de mieux cerner les conditions qui permettraient à terme de faire la distinction entre les filets frais et des filets congelés/décongelés. / Much appreciated by consumers for its nutritional qualities, seafood plays an important role in human diet. Consumer confidence in the quality of these foodstuffs is nevertheless affected by concerns about risks associated with exposure to chemical contaminants and the freshness of these products. If the first of these is the result of pollution resulting from increasing human activities along coastlines, the second is linked to the highly perishable nature of these products. An evaluation of the levels of chemical contaminants in seafood and of its freshness is therefore a necessity. It is within this context that the work presented in this thesis was carried out. Two principal objectives were targeted in the present study. The first objective of this work was to evaluate the spatial and seasonal variability of seafood contamination by elements (including metals) and organic pollutants (PAHs and PCBs) along the Senegalese coast. We studied 7 marine species representative of different trophic level (a green macro algae, a bivalve mollusc, a crustacean and 4 species of fish) sampling them along the coastline at 5 sites representing different human activity pressur. The result of this study showed that contamination levels varied with species, underlining the importance of a multi-species approach to study contamination in the marine environment. Variations between sites were also observed. Sites with the greatest human activity, such as Soumbédioune and Rufisque, were also those where the highest levels of contaminants in seafood were found. The levels of contamination measured along the Senegalese coast, of both elements and organic pollutants, were inferior or of the same order of magnitude as those reported from other West African sites or from other regions of the globe. The risks associated with eating theseseafood products were low, with contaminant levels generally below the admissible limits (EU) for human consumption. Only a few samples of certain species (mussels, sardines) exceeded these limits at Soumbédioune and Rufisque. The second objective of this study was to develop methods to evaluate the freshness of fish fillets, and to distinguish fresh fillets from previously frozen ones. The methods developed were based upon a measure of cellular permeability within the fish muscle tissue. The conservation of fish fillets ar 4°C results in increased permeability of cells over time, measurable by studying the liberation of intra-cytoplasmic enzymes or the increasing permeability of cells to fluorescent colouring agents. The measurements of lactate dehydrogenase (LDH) is doubly interesting in this contex : on the one hand it enables a measure of cell lysis, and so the level of alteration of the fillets over time, to be established. It also, thanks to its sensitivity to freezing, to better distinguish fresh fillets from those that have been frozen then thawed.