From: Andy Soos, ENN
Published July 1, 2010 02:30 PM

Dispersants in the Gulf

EPA continues to carefully monitor BP’s use of dispersant in the Gulf. Dispersants are generally less toxic than oil and can help prevent some oil from impacting sensitive areas along the Gulf Coast. EPA believes BP should use as little dispersant as necessary and, on May 23, EPA directed BP to reduce dispersant usage by 75 percent from peak usage. EPA and the Coast Guard formalized that order in a directive to BP on May 26. Over the next month BP reduced dispersant use 68 percent from that peak and EPA will continue to urge BP to reduce the volumes used. However, dispersants come in many varieties with different effectiveness and toxicity. EPA has just released a study of such available options.


A dispersant or a dispersing agent is either a non-surface active polymer or a surface active substance added to improve the separation of particles and to prevent settling or clumping. In simple language, this is no different than what a laundry detergent does. In this case dispersants are the type that help break up oil and cause it to disperse.

BP had earlier reported to EPA that they were unable to find a dispersant that is less toxic than Corexit 9500, the product currently in use in the Gulf of Mexico.

Following BP’s response, EPA began its own scientific testing of eight dispersant products on the National Contingency Plan Product Schedule. These were selected based on commercial availability for the Gulf clean up. Those dispersant products are: Dispersit SPC 1000, Nokomis 3-F4, Nokomis 3-AA, ZI-400, SAF-RON GOLD, Sea Brat #4, Corexit 9500 A and JD-2000. On June 30, EPA released peer reviewed results from the first round of its own independent toxicity testing on these eight oil dispersants.

These tests study the toxicity to selected aquatic species. These species are believed to be more sensitive to bio-toxicity effects. The test is simply whether the aquatic species survives exposure to the selected dispersant use level.

EPA's results indicated that none of the eight dispersants tested, including the product in use in the Gulf, displayed biologically significant endocrine disrupting activity.

While the dispersant products alone – not mixed with oil - have roughly the same impact on aquatic life, JD-2000 and Corexit 9500 were generally less toxic to small fish and JD-2000 and SAF-RON GOLD were least toxic to mysid shrimp. The dispersant in use in the Gulf causes no greater risk than any other dispersant available.

While this is important information to have and indicates no obvious or known problems, additional testing is needed to provide further information on how the dispersants combined with the oil may increase or decrease toxicity threats. The next phase of EPA’s testing will assess at the acute toxicity of multiple concentrations of Louisiana Sweet Crude Oil alone and combinations of Louisiana Sweet Crude Oil with each of the eight dispersants for two test species.

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