The scientific goal of this research is to elucidate the highly toxic compounds within fresh and weathered crude oil from the MC252 oil spill. The hypothesis of this research proposal is that a relatively small group of the chemicals in oil accounts for most of the toxicity. Learning the identity of these highly toxic compounds will lead to better predictions of the toxic properties of fresh crude oil and will provide a way to follow these substances as oil weathers in the environment. Oil residues from various sites differ in their composition and toxic activity. Furthermore, oil constituents change dramatically with time and weathering. The ability to identify and quantitate the key toxic compounds in oil will permit predictions of adverse human health effects and ecotoxicity in the future.
In human and environmental risk assessment studies, the first steps are hazard identification and dose-response analysis. Oil spills are well recognized for causing toxic effects in people and environmental organisms. However, oil is chemically complex and the specific compounds that contribute to its toxicity are surprisingly poorly defined. Polycyclic aromatic hydrocarbons (PAHs) represent a large family of toxic chemicals in oil. PAHs have received considerable attention from scientists. However, most of this previous research has focused on the PAHs produced by combustion (pyrogenic products), and these are not well represented in oil. The petrogenic PAHs in oil are distinct in that they are generally alkylated and most have never been evaluated for toxicity. A review article from this research team (Envir. Health Perspect. 122, 6-9, 2014) highlighted the need for toxicological characterization of the PAHs and other toxic chemicals (e.g. benzothiophenes, naphthaenoaromatics, etc.,) in oil. This proposal will help to fill this knowledge gap.
The marriage of analytical chemical methodologies with cellular bioassays to identify the highly toxic compounds within fresh and weathered oil samples is proposed here. Dr. Miller has developed an established bioassay that identifies the presence and relative potencies of PAHs and structurally related chemicals that activate the aryl hydrocarbon receptor (AhR). Activation of AhR is the key initial step in a signaling pathway that ultimately results in toxicity, and this bioassay provides the screening system to identify toxic components of oil. Dr. Overton is an expert in using analytical chemical approaches to separate and identify compounds in fresh and weathered crude oils. His group has the ability to fractionate and characterize the many compounds within oil. Drs. Wickliffe and Wilson have developed a novel genotoxicity assay based on normal human cell lines (RPTEC/TERT1 and HepaRG cells). These renal and hepatic cell lines represent toxicologically relevant targets for evaluating the mutagenic action of oil compounds. Dr. Overton and colleagues will prepare fractionated oil samples, Dr. Miller’s lab group will identify which of those fractions have the greatest AhR activity, and the active fractions will be evaluated in the cell lines for genotoxicity. Fractions with the greatest activity will be analyzed for chemical content and then re-fractionated by the Overton group. This fractionate and assay process will be repeated until the individual toxic compounds are identified. The ultimate goal of this research is to use these identified toxic compounds as a gauge of toxicity for any fresh or aged oil sample.
Project Research Overview (2016):
An overview of the proposed research activities from the GoMRI 2016 Meeting in Tampa.
Direct link to the Research Overview presentation.