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Comparative Toxicity of Eight Oil Dispersants, Louisiana Sweet Crude Oil (LSC) and Chemically Dispersed LSC to Two Aquatic Test Species
Citation:
HEMMER, M. J., M. G. BARRON, AND R. M. GREENE. Comparative Toxicity of Eight Oil Dispersants, Louisiana Sweet Crude Oil (LSC) and Chemically Dispersed LSC to Two Aquatic Test Species. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 30(10):2244-2252, (2011).
Impact/Purpose:
Assess the acute toxicity of eight oil dispersants, LSC and dispersant/LSC mixtures using two aquatic test species; the mysid shrimp, Americamysis bahia and the inland silverside, Menida beryllina. Results gained from these exposures were used to evaluate dispersant and dispersant/oil toxicity to improve our understanding of potential toxicological effects associated with dispersant use and help inform future decision-making during oil spill events.
Description:
This study describes the acute toxicity of eight commercial oil dispersants, Louisiana sweet crude oil (LSC), and chemically dispersed LSC. The approach utilized consistent test methodologies within a single laboratory in assessing the relative acute toxicity of the eight dispersants, including Corexit 9500A, the predominant dispersant applied during the DeepWater Horizon spill in the Gulf of Mexico. Static acute toxicity tests were performed using two Gulf of Mexico estuarine test species, the mysid shrimp (Americamysis bahia) and the inland silversides (Menidia beryllina). Dispersant-only test solutions were prepared with high energy mixing, while water accommodated fractions of LSC and chemically dispersed LSC were prepared with moderate energy followed by settling and testing of the aqueous phase. LC50 values for the dispersant-only tests were calculated using nominal concentrations whereas tests conducted with LSC alone and dispersed LSC were based on measured total petroleum hydrocarbon concentrations (mg TPH/L). For all eight dispersants in both test species, the dispersants alone were less toxic (LC50s: 3 to >5600 ppm) than the dispersant-LSC mixtures (0.4 to 13 ppm; mg TPH/L). LSC alone had generally similar toxicity to mysids (LC50: 2.7 ppm) and Menidia (LC50: 3.5 ppm) as the dispersant-LSC mixtures. The results of this study indicate that Corexit 9500A had generally similar toxicity as other available dispersants when tested alone and as a mixture with LSC.
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Comparative Toxicity of Eight Oil Dispersants, Louisiana Sweet Crude Oil (LSC) and Chemically Dispersed LSC to Two Aquatic Test Species