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The introduction of lux genes, able to express bioluminescence, into terrestrial bacteria enabled the optimisation of a bioluminescence-based bioassay that was environmentally relevant. Individual assay parameters such as growth phase, cell washing, lyophilisation, pH tolerance and temporal response to a range of metal and xenobiotic pollutants were evaluated. The effects of a range of pollutants upon the metabolic response of the lux-marked organisms were assessed using declines in bioluminescence. The lux -based bioassay proved more sensitive to the sub-lethal effects of metal pollutants than tests relying on culturability. Uncontaminated soils were spiked with metal and xenobiotic solutions both as single pollutants and in combination with other contaminants. Relative toxicity of metal and xenobiotic pollutants in soil systems were investigated using ecotoxicity assays based upon lux-marked constructs of Rhizobium leguminosarum biovar trifolii (an important associative nitrogen fixer) and the respiration of the microbial community. The lux-marked bioassay proved to be more sensitive than the community microbial assay to the presence of multiple contaminants at sub-lethal concentrations. The relative toxicities of metal and organic xenobiotic compounds were shown to be time dependent and better represented using chronic assaying of lux-marked microorganisms. Following a field trial involving the application of paper mill sludge to land and subsequent crop failure a rapid diagnosis of soil pollutants was required. A suite of ecotoxicity assays including lux-based bioassays, respirometry and enzyme activity were used to assess the toxicity of paper mill sludge to the soil microbial biomass. The selected lux-marked soil bacteria showed potential for use as rapid, field-based screening techniques to provide early warning of the potential hazards of waste application.

Glyphosate based herbicides are among the most widely used herbicides in the world. The purpose of this study was to determine developmental toxicity of glyphosate, the active ingredient in the common herbicide Roundup, on developing chicken embryos. Few studies have examined toxic effects of glyphosate alone versus the full compound formulations of Roundup, which include adjuvants and surfactants. Adjutants and surfactants are added to aid in solubility and absorption of glyphosate. In this study chicken embryos were exposed at the air cell on embryonic day 6 to 19.8 or 9.9 mg / Kg egg mass of glyphosate in Roundup or glyphosate only. Chickens treated with 19.8 and 9.9 mg / Kg glyphosate in Roundup showed significant reduction in survivability compared to glyphosate alone treatments and controls. On embryonic day 18, embryos were sacrificed for evaluation of developmental toxicity using wet embryo mass, dry embryo mass, and yolk mass as indicators. Morphology measurements were taken on liver mass, heart mass, tibiotarsus length and beak length. Embryos treated with 19.8 mg / Kg glyphosate and 9.9 mg / Kg glyphosate in Roundup showed significant reductions in wet and dry embryo mass and yolk mass. Tibiotarsus length in 9.9 mg / Kg glyphosate in Roundup treatments were significantly reduced compared to 9.9 mg / Kg glyphosate treatments. Beak length was significantly reduced in 9.9 mg /Kg glyphosate in Roundup treatments compared to all other groups.

Tributyltin is arguably the most toxic compound ever to be deliberately introduced into the marine environment as an ingredient of antifouling paints. It has had widespread toxic effects on a range of marine organisms, with some gastropod species being particularly sensitive. Effects of TBT on non-target species have resulted in partial bans on its use in many countries, so that new inputs to the water column have decreased in most areas. One of the physicochemical features of TBT is that it is readily sequestered by suspended particulates due to its low solubility and its hydrophobicity, therefore becoming incorporated into estuarine sediments. The availability of this sediment-bound TBT has been investigated through its potential for re-release back to the water column, and directly from the sediment using the sediment dwelling gastropod Hinia reticulata. The sorption process itself has been investigated using natural components to determine the sediment-water partition coefficient (Kd) together with factors affecting its magnitude. Sorption by sediments has been shown to be rapid (minutes), although the achievement of equilibrium may take longer (hours), and exhibits a Freundlich-like dependence on the TBT concentration due to the variable energies of TBT sorption sites on sediment particles. The major determinant of Kd is sediment type, greater adsorption occurring in fine-grained organic rich sediments compared to low organic sands; although both salinity and pH modify the degree of adsorption. The sorption process has been shown to be reversible, so that previously contaminated sediments may act as reservoirs of TBT, releasing the compound back to the overlying water for many years. Hinia reticulate has been shown to be an effective and quantitative accumulator of both dissolved and sediment-bound TBT, principally acquiring TBT from water across the respiratory surfaces. When additionally exposed to sediments, significantly higher body burdens were accumulated, with up to 80% of the total attributable to the sediment. Uptake of TBT across the surface of the headtfoot appears to be an important pathway for sediment-exposed Hinia reticulata, while the ingestion of contaminated sediment does not appear to occur. Hinia reticulata is capable of metabolising TBT to lesser butylated and presumably less toxic products which are excreted, making its accumulated body burdens responsive to changing environmental TBT levels, and increasing its value as a biomonitor When exposed to a range of TBT contaminated sediments, Hinia reticulata showed there to be greater TBT availability from sediments with a low sorptive capacity (sands), principally through desorption of TBT to the overlying water. Fine-grained organic-rich muds, which have a greater capacity for TBT, produced lower accumulated burdens in Hinia reticulata, but may represent more important long-term sources of TBT to benthic organisms in estuaries.

Submitted in partial fulfilment of the requirements for the degree of Master of Public Health, in the field of Maternal and Child Health, to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, September 2014 / Introduction: Nevirapine (NVP) is used in combination antiretroviral treatment especially for pregnant HIV infected women. NVP has been shown to be inferior and more toxic than other similar drugs, but continues to be used in developing countries due to cost. Aim: This study aimed to determine the prevalence of NVP toxicity and associated factors among 478 pregnant women from three public health facilities in inner city Johannesburg. Materials and methods: We employed a cross-sectional retrospective record review study design to analyse the records of 478 pregnant women in the above mentioned public health facilities. Variables including demographic (age, weight, gestational age) and clinical (CD4 cell count, WHO HIV clinical stage, prior ART experience) characteristics were extracted and the association between these characteristics and the development of toxicity post NVP exposure was explored. Results: The study found that approximately nine out of ten women (89.5%) were ART naïve at the time of NVP initiation. When compared with ART naïve women, ART experienced women had a slightly higher mean CD4 cell count, however, for both groups of women, mean CD4 cell count was less than 250 cells/mm3. Overall, 85.1% of women had a CD4 cell count less than 250 cells/mm3. More than half (55.3%) of the women were in the third trimester of pregnancy and the majority (82%) classified as WHO HIV clinical stage one. At least one adverse event was reported in 63 (13.2%) women. Mild skin rash was the most prevalent adverse event, occurring in 9.6% of women. Hepatotoxicity occurred in 5.3% of women and severe skin rash occurred in 1.5% of women. Almost 85% of adverse events occurred in women with CD4 cell counts <250 cells/mm3. WHO HIV clinical stage II and IV were significantly associated with the overall development of toxicity (ρ <0.01). Conclusions: Whilst the overall prevalence of mild and severe skin rash in this sample was less than that demonstrated in earlier studies, a higher overall prevalence of hepatotoxicity was found. When compared with ART naïve women, ART experienced women were found to have a higher prevalence of mild skin rash. Hepatotoxicity and severe skin rash only occurred in ART naïve women. In this sample, CD4 cell count ≥250 cells/mm3 was not associated with the development of NVP adverse events. Recommendations: Our findings support the continued use of NVP as part of combination ART regimens in women of African descent. In contrast with previously published data, our study showed a significant association between WHO HIV clinical stage and NVP toxicity, our study also included relatively few women with higher CD4 cell counts. Further research including predominantly healthy HIV infected pregnant African women as well as women with higher CD4 cell counts is required in order to fully explore the association between these variables and the development of NVP post-exposure toxicity.