Risk assessment of complex mixtures of polycyclic aromatic hydrocarbons (PAHs) at superfund sites /
This research was designed to determine whether a component-
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736824201&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This research was designed to determine whether a component- based chemical characterization can effectively predict the same mutagenic (and ultimately, carcinogenic) potential of a whole-mixture extract as detectable in direct in vitro testing. In so doing, soil and waste samples were collected at "Superfund" sites planning or undergoing remediation for extraction. Extracts were tested qualitatively and quantitatively for mutagenicity using the Salmonella/microsome and/or the E. coli prophage induction assays. Quantitative and qualitative chemical analysis formed the basis for the cancer risk assessment, which was intended to provide a component-based estimate of the carcinogenic potential of the mixture extracts based on an assumption of additivity. The chemical component-based risk assessment includes a limited number of specific carcinogenic components, whereas the results of the in vitro genotoxicity assays were shown to reflect the response of the whole complex mixture extract. No clear-cut correlations held for all four sites described when either specific or weighted mutagenic activity values were compared with estimated lifetime cancer risk. The striking absence of mutagenicity in the Site 4 sample that carried a plausible upper bound excess cancer incidence of 238 per million exposed population is one example of how biological testing (especially a single endpoint) alone may not be a reliable measure of risk. At the same time, results from testing of Site 1 samples indicated that although treatment and dilution of highly contaminated soils greatly decreased the resultant cancer risk to below target levels, a battery of genotoxicity assays could not confirm the risk assessment findings. Departures between direct whole-mixture in vitro mutagenicity testing and carcinogenic potential based on additive, component-based calculations were investigated. This research thus determined that the component-based approach to cancer risk assessment of complex mixtures described here did not concur with the direct in vitro whole-mixture approach to assessing mutagenic (and ultimately, carcinogenic) potential. |
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| Item Description: | Vita. "Major Subject: Toxicology". |
| Physical Description: | xiv, 181 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 131-143. |