Aquatic toxicity of two Corexit dispersants.

The oil spill dispersants, Corexit 9500 and Corexit 9527 have low to moderate toxicity to most aquatic species in laboratory tests. Toxicity estimates are significantly affected by test variables such as species, lifestage, exposure duration, and temperature. Aquatic toxicity data generated from spiked, declining exposures (107 min half-life) are more reflective of actual dispersant use conditions. Decisions to use oil spill response chemicals should not be based solely on aquatic toxicity. Factors to consider include product effectiveness, toxicity of dispersed oil, species/habitats requiring priority protection, and recovery potential of sensitive habitats and populations. An environmental risk assessment approach is recommended where dispersant toxicity data generated under environmentally relevant exposures are compared to estimated environmental concentrations of dispersants.