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Mechanisms of Oil Toxicity: Relevance to Impact Assessment and Spill Response
Citation:
Barron, M. Mechanisms of Oil Toxicity: Relevance to Impact Assessment and Spill Response. SpillCon and Spill Master Class, Perth, WA, AUSTRALIA, May 16 - 24, 2019.
Impact/Purpose:
The purpose of this invited presentation is to summarize oil toxicity mechanisms at the Australian government Oil Spill Master Class in Perth Australia. The presentation is impactful because the Class is attended by and my presentation will be heard by spill responders, oil spill scientists, and risk managers from around the globe. EPA will continue to be recognized for our international expertise in oil toxicology. Dr. Barron's participation in the Class will also allow him to maintain and expand his state of the science expertise by attending other presentations and interacting with other global experts in spill response science. Maintaining Dr. Barron's international expertise is impactful to EPA because of the Agency's reliance on him as a technical advisor and testifying expert.
Description:
Oil can cause toxicity through physical coating of organisms and habitats, and systemic effects through uptake of petroleum hydrocarbons. This presentation will focus on mechanisms of oil toxicity in aquatic organisms relevant to impact assessment and spill response in aquatic environments. Early studies of oil toxicity identified small aromatics such as alkyl benzenes and naphthalenes as primary chemicals of concern in spilled oil because of their relatively high abundance, water solubility, and rapid partitioning into aquatic organisms. These compounds were observed to cause toxicity through a narcosis mode of action, similar to the reversible anesthetic-like effects seen with solvents and other chemicals of moderate polarity. Research on larger PAHs such as benzo(a)pyrene showed the ability to induce oxidative biotransformation systems and form potentially mutagenic compounds. Beginning in the 1980s, research showed that polycyclic aromatic hydrocarbons (PAHs) with specific structural conformations could cause toxicity through a unique mode of action known as photoenhanced toxicity through interaction of the PAH with ultraviolet radiation present in sunlight. Following the Exxon Valdez oil spill, species of salmon and herring exhibited a syndrome of edema and skeletal malformations similar to dioxin toxicity. Subsequent research identified specific three ring and larger PAHs and heterocyclic compounds as causing a characteristic suite of cardiotoxicity and other embryotoxic effects in multiple species of freshwater and marine fish exposed to crude or heavy oils. Photoenhanced toxicity and developmental cardiotoxicity at part per billion concentrations were shown to be important injury pathways following the Deepwater Horizon oil spill. Together this body of research shows that petroleum hydrocarbons can act through distinct mechanisms with differing time frames and organismal-level outcomes. Oil toxicity mechanisms are an important consideration in spill response and impact assessment as determinants of life stage and organism sensitivity and exposure levels of concern.