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You searched for +publisher:"Texas A&M University" +contributor:("Duncan, Bruce"). Showing records 1 – 2 of 2 total matches.

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1. Gillespie, Annika Margaret. Environmental toxicity of complex chemical mixtures.

Degree: PhD, Toxicology, 2009, Texas A&M University

Complex chemical mixtures may be released into the environment from a variety of sources including hazardous waste sites. Components of chemical mixtures and their metabolites may be genotoxic leading to cancer and heritable gene mutations. Chemical analysis alone does not always provide the most accurate information from which to estimate the risk of adverse effects associated with exposure to mixtures. Current methods to estimate the human health risk for complex mixtures assume additive effects of the components. Although it is assumed that this approach is protective of human and ecological health, it is also recognized that chemical mixtures may induce a variety of interactions including potentiation, synergism, and antagonism. A combined testing protocol, using chemical analysis coupled with a battery of in vitro, in vivo, and in situ bioassays, provides the most accurate information from which to estimate risk. Such a combined testing protocol provides information to describe the major organic and inorganic constituents, as well as the pharmacokinetics and potential interactions of chemical mixtures. This research was conducted to investigate the potential genotoxic effects of complex chemical mixtures of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated aromatics (PCA) using microbial bioassays (Salmonella/microsome assay and the E. coli prophage induction assay), the 32P-postlabeling assay in mice, and in situ measurements of genotoxicity using flow cytometry. Samples of environmental media and wildlife tissues were collected from four National Priority List Superfund sites within the United States. In general, chemical analysis was not always predictive of mixture toxicity. Although biodegradation reduced the concentration of total and carcinogenic PAHs in soils and groundwater, the genotoxicity of extracts from environmental media did not display a corresponding reduction. Mixtures of polychlorinated biphenyls (PCBs) extracted from sediments were found to inhibit the genotoxicity of PAH mixtures when administered dermally to rodents. This inhibition exhibited a dose-response relationship, with the adduct frequency reduced at increasing doses of sediment extract. Finally, PAH concentrations in environmental media and tissues were found to correlate with DNA damage in wildlife receptors. An integrated approach, combining in vitro and in vivo methods to characterize genotoxicity provides more accurate information from which to estimate uptake and risk associated with exposure to complex mixtures and should be considered in both the human and ecological risk assessment process. Advisors/Committee Members: DONNELLY, K.C. (advisor), AUTENRIETH, ROBIN L. (committee member), BICKHAM, JOHN W. (committee member), DUNCAN, BRUCE (committee member), McDONALD, THOMAS J. (committee member).

Subjects/Keywords: ENVIRONMENTAL TOXICOLOGY; COMPLEX CHEMICAL MIXTURES; GENOTOXICITY; ECOTOXICOLOGY; RISK ASSESSMENT; TOXICOLOGY

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Gillespie, A. M. (2009). Environmental toxicity of complex chemical mixtures. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/ETD-TAMU-1017

Chicago Manual of Style (16th Edition):

Gillespie, Annika Margaret. “Environmental toxicity of complex chemical mixtures.” 2009. Doctoral Dissertation, Texas A&M University. Accessed October 31, 2020. http://hdl.handle.net/1969.1/ETD-TAMU-1017.

MLA Handbook (7th Edition):

Gillespie, Annika Margaret. “Environmental toxicity of complex chemical mixtures.” 2009. Web. 31 Oct 2020.

Vancouver:

Gillespie AM. Environmental toxicity of complex chemical mixtures. [Internet] [Doctoral dissertation]. Texas A&M University; 2009. [cited 2020 Oct 31]. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-1017.

Council of Science Editors:

Gillespie AM. Environmental toxicity of complex chemical mixtures. [Doctoral Dissertation]. Texas A&M University; 2009. Available from: http://hdl.handle.net/1969.1/ETD-TAMU-1017


Texas A&M University

2. Kelley, Matthew A. Evaluation of Sediment Toxicity Using a Suite of Assessment Tools.

Degree: PhD, Toxicology, 2010, Texas A&M University

Accurate characterization of risk of adverse ecological effects related to contaminated sediment presents a particularly difficult challenge. A series of studies has been conducted to investigate the utility of various tools for assessment of sediment toxicity. The goal of this research was to provide information which could help increase the accuracy with which predictions of toxicity could be made at hazardous sites. A calibration study was conducted using model PAHs, PCBs, a binary PAH mixture and a coal-tar mixture. This study was a collaborative effort among five university-based Superfund Research Programs (SRPs). Each program, with the help of funding through the NIEHS Superfund Research Program, has developed a chemical-class specific assay to estimate toxicity of contaminants in sediment. This suite of bioassays expands the range of data typically obtained through the use of standard aquatic toxicity assays. A series of caged in situ exposure studies has been conducted using juvenile Chinook salmon and Pacific staghorn sculpin in the Lower Duwamish Waterway. The study aimed to investigate the utility of selected biomarkers in evaluating the relationship between contaminants present in environmental samples and response in receptors following an in situ caged exposure. Results found that DNA adducts detected in exposed fish were significantly higher than controls in 2004 and 2006, and DNA adducts appear to be a reliable indicator of exposure, although no dose-response relationship was present. Western blot analysis of CYP1A1 was not indicative of exposure levels. The final study conducted was concerned with evaluating the utility of using solid phase microextraction (SPME) fibers in situ to evaluate contaminated sediment. Levels of PAHs and PCBs in sediment often exceeded sediment quality guidelines; however, results from aquatic toxicity bioassays using Hyalella azteca were mostly negative, thus levels of contaminants detected on SPME fibers could not be associated with adverse effects in Hyalella. However, regression analysis of total PAHs present in sediment and levels of PAHs detected in porewater SPME fiber samplers, which were placed 5 cm into the sediment for 30 days, revealed a strongly correlated linear relationship (R2 = .779). Normalization of the sediment data to total organic carbon was performed to determine if the trend would remain present, and the linear relationship was again confirmed (R2 =.709). Advisors/Committee Members: McDonald, Thomas (advisor), Duncan, Bruce (committee member), Phillips, Timothy (committee member), Sayes, Christie (committee member).

Subjects/Keywords: Sediment; PAHs; PCBs; DNA adducts; Solid Phase Microextraction; SPME

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Kelley, M. A. (2010). Evaluation of Sediment Toxicity Using a Suite of Assessment Tools. (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/149206

Chicago Manual of Style (16th Edition):

Kelley, Matthew A. “Evaluation of Sediment Toxicity Using a Suite of Assessment Tools.” 2010. Doctoral Dissertation, Texas A&M University. Accessed October 31, 2020. http://hdl.handle.net/1969.1/149206.

MLA Handbook (7th Edition):

Kelley, Matthew A. “Evaluation of Sediment Toxicity Using a Suite of Assessment Tools.” 2010. Web. 31 Oct 2020.

Vancouver:

Kelley MA. Evaluation of Sediment Toxicity Using a Suite of Assessment Tools. [Internet] [Doctoral dissertation]. Texas A&M University; 2010. [cited 2020 Oct 31]. Available from: http://hdl.handle.net/1969.1/149206.

Council of Science Editors:

Kelley MA. Evaluation of Sediment Toxicity Using a Suite of Assessment Tools. [Doctoral Dissertation]. Texas A&M University; 2010. Available from: http://hdl.handle.net/1969.1/149206

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