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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

A lux-based bioassay of heavy metal contamination of organic wastes

Sarin, Charoon January 2000 (has links)
The luxCDABE genes (i.e. full cassette) were inserted into the bacterial strain used in this study, E. coli HB101, using a multi copy plasmid, (pUCD607). A number of experiments were carried out in this thesis to study the potential of using the biosensor, E. coli HB101 (pUCD607), for ecotoxicity testing. Growth and bioluminescence of E. coli HB101 (pUCD607) were characterised and optimised, as well as the stability of this biosensor to a range of environmental parameters. The biosensors were found to be sensitive to a range of pollutants and provided a highly consistent bioluminescence response under conditions likely to be encountered in environmental toxicity testing. Assessment of the potential of the lux-based bioassay for revealing the combination of toxicities of metals was carried out. This is necessary because samples in ecotoxicity testing may contain a number of types of pollutants. The biosensors showed high sensitivity of response to mixed metals and identified the combined toxicity of the mixture. Biosensor bioluminescence could also be used to diagnose the distinction between toxicity after 15 and 30 minutes exposure. Results suggested that exposure time is an important factor affecting on the toxicity of metals in mixtures. The results from challenging lux-based biosensors with heavy metals with various concentration of Cl- demonstrated the effect of Cl- ion complex formation for metals on the bioluminescence of E. coli HB101 (pUCD607). The bioluminescence response of the biosensor also related to the results from computer modelling (GEOCHEM) and was used to diagnose the effect of Cl- on metal toxicity. The results showed that E. coli HB101 (pUCD607) is sensitive to complexes of metals such as are formed by Cl- ion. Immobilised cells of E. coli HB101 (pUCD607) were used to investigate the toxicity of metals, both singly and in mixture. This work aimed to assess the potential of immobilised cells, as an alternative form of biosensor, for use in ecotoxicity testing. Bioluminescence response of immobilised cells varied with the test solution pH and showed that it has great potential for use in low pH environments. Immobilised cell biosensors demonstrated sufficient sensitivity to identify the toxicity of individual and mixed metals. High levels of bioluminescence of immobilised cells lasted up to 5 hours after bead production, suggesting that biosensor immobilisation increases the flexibility of the toxicity assay.
52

Evaluation of the effect of air pollution on human health in Kuwait

Al-Kandari, Mariam Hussain Murad January 1994 (has links)
Even before the 1990 war the populations of some areas of Kuwait was subject to severe atmospheric pollution. However, little was known about the effect of this pollution on health and on the use of health care. Three areas in Kuwait were chosen for study which were demographically similar and lay at a different distances to the north (i.e. usually downwind) of the industrial area. Plant in this area emits hydrogen sulphide, sulphur dioxide, hydrocarbons, nitrogen oxides, ammonia and carbon monoxide among other pollutants. A special survey was carried out to gather information on demographic, health and lifestyle factors including age, sex, place of residence, smoking, physical symptoms, psychological effects, life satisfaction, environmental problems, experience of air pollution and use of health care. A random sample of 136 households (1140 persons) was chosen from the three areas and studied over the period from lst February 1988 to 31st January 1989. Data on levels of pollution concentrations and meteorological conditions were also collected over the same period for each area studied. Data on use of health care were available from the health centres in the three areas studied and also from the population survey. The demographic similarity of the three areas studied was generally confirmed by the data from population survey. The relationships involved were examined for different age groups using cross tabulation, time series analysis and regression analysis. There were clear gradients with increased distance from the industrial area in levels of pollution, levels of selfreported physical and psychological symptoms and in the use of health care. Of the individual pollutants it appeared that carbon monoxide levels were most closely correlated with levels of symptoms. For those aged less than 18, the link to CO was closest for respiratory symptoms, while for those aged 18 to 64 the link was with headache. The use of primary care is more closely linked to H2S although this relationship is relatively weak. Consider the relationship between levels of pollution in the three areas studied and Kuwait City and the levels of pollution in Shuaiba area taking meteorological conditions into account. The purpose of this was to allow for estimates of the effect of pollution reduction in Shuaiba on the health of population elsewhere in the country. However, no way was and of making such estimates with sufficient prison. This analysis confirmed a number of recommendations that have been made by others.
53

Appraisal and validation of rapid, integrated chemical and biological assays of environmental quality

Fillmann, Gilberto January 2001 (has links)
To assess the significance of pollutants released into the environment it is necessary to determine both the extent of contamination and the biological effects they give rise to. This research is based on a tiered system, which commences with conventional analytical chemistry (gas chromatography), followed by the development, evaluation and application of rapid and simple immunochemical techniques and, finally, the integration of chemical and biological markers to assess pollution. GC-ECD/FID/MS have been used to investigate the status of chemical contamination of the Black Sea by organochlorine residues, hydrocarbons and faecal sterols. Useful information is provided and problems with e.g. HCHs and sewage contamination are highlighted. Contamination by DDTs, PCBs, "total" hydrocarbons and PAHs is also reported. Next, these techniques are used to develop rapid screening methods. Four distinct applications of immunochemical techniques are presented. Initially, the BTEX RaPDD Assay® ELISA is evaluated to detect semi-volatile hydrocarbons in contaminated groundwater. Although overestimating concentrations when compared to GC-FID/PID, results are well correlated. Secondly, the effectiveness o f the BTEX and c-PAH RaPID Assay® to detect hydrocarbons in sediments is tested. Once again, good agreement with GC-FID/MS confirms the ELISA to be a useful screening protocol to focus more expensive high-resolution analytical techniques. The adaptability and applicability of an ELISA (PCB RaPID Assay®) method in measuring "total" PCB levels in mussel tissue is demonstrated. An underestimation of concentrations, despite of covariability between ELISA and cGC-ECD, is discussed. Next, ELISA (RaPID Assay®) and fluorometry were successfully applied to quantify PAH metabolites in crab urine as a measure of exposure. HPLC analyses indicated that conjugate PAH metabolites were dominant in urine of crabs exposed to pyrene. Differences could also be identified between crabs taken from clean and contaminated sites. Finally, an integration of chemical and biological techniques is used to investigate contamination and effects in mussels within a pollution gradient. Results indicate a correlation between micronucleus formation, heart rate and PCB and PAH level.
54

Lead exposure and its impact on the health of adolescents: the birth to twenty cohort

Naicker, Nisha 04 March 2013 (has links)
Introduction Lead exposure continues to be a major public health issue in South Africa, and other low and middle income countries. Environmental lead exposure has been associated with detrimental health effects in children. The aim of this thesis was to assess the prevalence of lead exposure and its association with various risk factors, its effects on puberty and socio-behavioural adjustment in adolescents. Methods The Birth to Twenty (Bt20) cohort study started in 1990, and is a long-term prospective follow-up study of children’s health and well-being. Mothers were recruited from antenatal clinics in the Johannesburg-Soweto metropolitan area between April and June 1990 (n=3273). Lead levels were analysed in samples of cord blood collected at birth (n=618) and whole venous blood collected at 13 years of age (n=1546). Data on selected child, maternal and household factors were collected using a structured questionnaire in the third trimester of pregnancy and at 13 years of age. Additional data on puberty (attainment of menarche and self-reported Tanner staging for breast and pubic development) and behaviour using the Youth Self Report was obtained at 13 years of age. Results In the Bt20 cohort the mean blood lead level at birth was 5.9 μg/dl, and at 13 years of age it was 5.7 μg/dl. The majority of children had blood lead levels above 5.0 μg/dl (52% at birth and 56% at 13 years). At birth, being a teenage mother and having low educational status were strong predictors for elevated cord blood lead levels. Being a male child, having an elevated cord blood level, and lack of household ownership of a phone were significant risk factors for high blood lead levels at 13 years. In 13 year old females with pubertal data (n= 682) the mean blood lead level was 4.9 μg/dl. Fifty percent had blood lead levels < 5.0 μg/dl, 49 % were ≥5.0 μg/dl and 1% was > 10.0 μg/dl. The average age of menarche was 12.7 years. At 13 years, 4% and 7% had reached Tanner stage 5 for pubic hair and breast development, respectively. Analyses showed that higher blood lead levels were significantly associated with delays in all measures of puberty (p <0.001). In the 13 year old sample with data on the Youth Self Report (n= 1041), the geometric mean blood lead level was significantly (P value<0.001) higher in boys (6.0 μg/dl) compared to girls (4.5 μg/dl). The bivariate analyses stratified by gender showed that boys’ blood lead levels were significantly associated with four types of aggressive behaviour. There were no significant associations found in girls. A multivariate analysis was conducted in the sample of boys and after adjusting for socio-economic factors ”Attacking People” remained significantly associated with blood lead levels. Conclusion Significant associations found in the study point to the low socio-economic status of lead exposed children. These poor circumstances frequently persist into adolescence resulting in continued high lead levels. Higher blood lead levels were associated with a delay in the onset of puberty in girls, and with anti-social behaviour among boys in early adolescence. Lead exposure in low and middle countries is generally higher compared to high income countries, and thus the effects of high blood levels are much greater and have larger personal and public health significance.
55

The transboundary transportation of pollutants from The Zambian Copperbelt

Dlamini, Simangele 10 February 2006 (has links)
Master of Science - Science / The transportation of aerosols and trace gas material from industrial activities and biomass burning in southern Africa has received widespread attention from scientists over the past decade. Dominant circulation patterns in the sub-region facilitate the southward transportation of sulphur pollutants from the pyromerturllugical processing of copper in Zambia and the Democratic Republic of Congo (DRC), and products of biomass burning from countries in the sub-region in general. This research focuses on the contribution of industrial pollutants from the Zambian Copperbelt and products of biomass burning in the sub-region to total aerosol loading over South Africa. The seasonality of air transport over the region in general, and South Africa in particular, is determined from different transport fields and their frequency of occurrence. Data supplied by the European Center for Medium Range Weather Forecasting (ECMWF) has been used to run trajectories for the summer, autumn, winter and spring seasons for southern Africa for the years 1990-1994. Forward trajectories have been calculated for the 850, 800, 750 and 700hPa geopotential heights, from Kitwe (12.9° S, 28.2° E, 1262m above mean sea level), at 2.5° resolution. The wall programme has been used as a tool for analysis. Trajectories show widespread recirculation over the subcontinent, resulting in a net transportation of sulphate aerosols from the Zambian Copperbelt. Biomass burning products are likely to join this plume, especially during the late winter and spring seasons. During the summer, air transport is mainly to the west, via Angola and the Democratic Republic of Congo, off the eastern Atlantic towards southern America.
56

The gas-chromatographic determination of trace organic pollutants in aqueous samples.

January 1986 (has links)
by Wu Siu Yu Portia. / Bibliography: leaves 105-107 / Thesis (M.Ph.)--Chinese University of Hong Kong
57

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
58

Cytochrome P4501A Induction by Highly Purified Hexachlorobenzene in Primary Cultures of Avian Hepatocytes

Mundy, Lukas 05 October 2011 (has links)
Hexachlorobenzene (HCB) is a persistent organic pollutant that was primarily produced for use as a fungicide dating back to the 1940s. Worldwide emissions have declined steadily over the past forty years, but HCB is still produced as a by-product of a number of industrial processes and is still detected in remote locations around the globe. Many studies have been conducted to determine the toxic and biochemical effects of HCB, but it has been suggested that reported toxic and biochemical effects initially attributed to HCB exposure may have actually been elicited by contamination of HCB by polychlororinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs). This thesis investigates whether highly purified HCB (HCB-P; defined as HCB containing < 0.2 ppb of any PCDD, PCDF, or co-planar PCB congener [the detection limit of current analytical methods]) can induce cytochrome P4501A (CYP1A) in three avian species in vitro. Primary cultures of chicken (Gallus gallus domesticus), ring-necked pheasant (Phasianus colchicus) and Japanese quail (Corturnix japonica) embryo hepatocytes were used to compare the potencies of reagent-grade (RG-HCB), HCB-P and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as inducers of ethoxyresorufin O-deethylase (EROD) activity, CYP1A4 messenger ribonucleic acid (mRNA) and CYP1A5 mRNA. The potencies of two mono-ortho substituted PCBs, 2,3,3’,4,4’-pentachlorobiphenyl (PCB 105) and 2,3’,4,4’,5-pentachlorobiphenyl (PCB 118) were also assessed in chicken embryo hepatocytes using the same endpoints. All compounds induced EROD activity and up-regulated CYP1A4/5 mRNAs in the hepatocytes of each species. The potency of HCB relative to the potency of TCDD (ReP) was 0.0001, 0.001 and 0.01 in chicken, ring-necked pheasant and Japanese quail embryo hepatocytes, respectively. ECthreshold values were suggested to be more appropriate than EC50 values because ECthreshold values account for differences in maximal EROD and CYP1A4/5 mRNA levels that are observed with HCB exposure in avian embryo hepatocytes more so than EC50 values. Differences in species sensitivity to HCB were also assessed, and did not vary as greatly as the listed ReP values. The results presented herein suggest that HCB is capable of inducing effects downstream of activation of the aryl hydrocarbon receptor, and may warrant its inclusion in the World Health Organization’s toxic equivalency concept.
59

Persistence and spatial range of environmental chemicals : new ethical and scientific concepts for risk assessment /

Scheringer, Martin. January 1900 (has links)
Based on a Ph. D. Thesis--ETH Zürich, 1996. / Includes bibliographical references and index.
60

Development of a quantitative model for binding cesium to SRS soils

Goto, Momoko 05 1900 (has links)
No description available.

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