Fractionation and risk assessment of complex environmental mixtures /
The focus of this research was to develop improved methods for complex mixtures risk assessment. The first objective was to compare two frequently employed methods for fractionating a wood preserving waste (WPW) containing polycyclic aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP). One meth...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2003.
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| Summary: | The focus of this research was to develop improved methods for complex mixtures risk assessment. The first objective was to compare two frequently employed methods for fractionating a wood preserving waste (WPW) containing polycyclic aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP). One method provided optimal separation and recovery of the PAHs, while the other was more successful at isolating and recovering PCP. The biological activity of the PCP, but not of the PAHs, was detected in the bioassays. This suggests that a refined hybrid method with further PAH isolation may be the best approach. The second objective was to characterize the genotoxicity of manufactured gas plant residue (MGP), and evaluate 7H-benzo[c]fluorene (BC) genotoxicity. Following dermal application to mice, the fraction with 3,900 ppm BC and 45,216 ppm cPAHs induced 41% more lung DNA adducts than the "BC fraction", which contained 35,000 ppm BC and 216,109 ppm cPAHs. The high dose of the BC fraction induced 15.2-fold more adducts than 0.10 mg BC, the quantity of BC present in the high dose of the BC fraction. This suggests that BC is not the dominant lung DNA adduct-forming component of dermally-applied MGP. The third objective was to evaluate whether the crude extract and acid, base and PAH-rich isolates from two WPWs containing PAHs and PCP were "sufficiently similar" according to recent (U.S. EPA, 2000; Versar, Inc. and BR Stern Associates, 2002) guidelines. Only two of the PAH-rich isolates were sufficiently similar chemically and biologically. Overall, biological activity could not be predicted using the chemical analyses. Fractionation was necessary to reveal biological activity. The final objective was to assess WPW developmental toxicity. The no observed adverse effect level (NOAEL) for the WPW in chick embryos was more than an order of magnitude lower than the U.S. EPA IRIS database NOAEL values for the priority PAHs or PCP, suggesting that this endpoint should be included in WPW toxicity assessments. Overall, fractionation was important for evaluating complex mixture toxicity. Chemical analysis and in vitro and in vivo assays should be used to evaluate the genotoxic, epigenetic and developmental toxicity of complex PAH/PCP mixtures. |
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| Item Description: | Vita. "Major Subject: Toxicology". |
| Physical Description: | xvii, 210 leaves : illustrations ; 28 cm. Issued also on microfiche from Lang Micrographics. |
| Bibliography: | Includes bibliographical references (leaves 175-196). |