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Oil and UV Interactions
Citation:
Barron, M. Oil and UV Interactions. SpillCon and Spill Master Class, Perth, WA, AUSTRALIA, May 16 - 24, 2019.
Impact/Purpose:
The purpose of this invited presentation is to summarize the influence of oil and sunlight interactions that influence toxicity 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:
Ultraviolet radiation (UV) in sunlight can interact with specific polycyclic aromatic hydrocarbon and heterocycle (PAH) components of oil through photo-oxidation and photoenhanced toxicity. Photo-oxidation is the chemical modification of PAHs into transient oxidized products that are generally more water soluble and less persistent, and can be an important pathway for oil degradation in high UV environments. Phototoxicity is the enhanced toxicity of oil in the presence of UV, caused by either the greater intrinsic toxicity of the photo-oxidized PAHs, or through a mechanism known as photo-sensitization. In photo-sensitization, unmodified PAHs are first bioaccumulated by an aquatic organism, then UV interacts with the accumulated residues within organism tissues. Phototoxicity is typically observed as a two to greater than 100-fold increase in chemical toxicity, and generally only occurs in the translucent early life stages of marine and freshwater fish and invertebrates. The mechanism of photosensitization is through rapid generation and cycling of reactive oxygen species causing tissue damage and death. Phototoxic PAHs are a small component of oil that have three to five fused rings and other specific structural requirements. Phototoxicity is determined by both chemical and UV exposure and can occur at environmental concentrations of PAHs (ug/L) and ambient light levels within the water column of many aquatic environments. UV interactions with oil should be considered in oil spill response and impact assessment as both a degradation process and potential mechanism for enhanced toxicity.