EPA Response to BP Spill in the Gulf of Mexico

EPA's Toxicity Testing of Dispersants

In response to the BP oil spill, EPA monitored air, water, sediment, and waste generated by the cleanup operations. Ongoing response and restoration efforts are posted to RestoreTheGulf.gov.

While emergency response data collection has ended, results continue to be available on this site. Any new data will continue to be posted to this site, and data will continue to be available here for the foreseeable future.

Much of the content of this site continues to be available for historical and information purposes, but we are no longer updating these pages on a regular basis.

EPA continues to carefully monitor BP’s use of dispersant in the Gulf. Dispersants are generally less toxic than oil and can 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, Administrator Jackson and then-Federal On-Scene Coordinator Rear Admiral Mary Landry 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 (PDF) (1pg). 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.

Prior to ordering BP to reduce dispersant usage, EPA directed BP to analyze potential alternative dispersants for toxicity and effectiveness. BP reported to EPA that they were unable to find a dispersant that is less toxic than Corexit 9500, the product currently in use.

On this page:

Results of the phase II testing
Results of the phase I testing
- Reports
- Audio and transcript of the June 30 press call

More information on dispersant use in the Gulf:

August 2 - Results of the Phase II Testing

EPA has completed the second phase of dispersant testing to assess 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 on the National Contingency Plan Product Schedule. The results indicate that the eight dispersants tested are similar to one another based on standard toxicity tests on sensitive aquatic organisms found in the Gulf. These results confirm that the dispersant used in response to the oil spill in the Gulf, Corexit 9500A, is generally no more or less toxic than the other available alternatives.

The organisms tested were two Gulf of Mexico aquatic species: (1) the mysid shrimp, Americamysis bahia, an aquatic invertebrate, and (2) the inland silverside, Menidia beryllina, a small estuarine fish. These species are standard test organisms used in toxicity tests for a variety of pollutants. The tests were conducted on mixtures of Louisiana Sweet Crude Oil and eight dispersant products found on the National Contingency Plan Product Schedule – Dispersit SPC 1000, Nokomis 3-F4, Nokomis 3-AA, ZI-400, SAFRON Gold, Sea Brat #4, Corexit 9500 A and JD 2000.

The results indicate that for all eight dispersants in both test species, the dispersants alone were less toxic than the dispersant-oil mixture. Oil alone was found to be more toxic to mysid shrimp than the eight dispersants when tested alone. Oil alone had similar toxicity to mysid shrimp as the dispersant-oil mixtures, with exception of the mixture of Nokomis 3-AA and oil, which was found to be more toxic.

These toxicity tests were conducted as part of an overall assessment of BP’s use of Corexit 9500 in response to the oil spill in the Gulf. These tests, coupled with EPA’s first round of dispersant tests show that dispersants are not distinguishable from one another based on the acute toxicity tests for sensitive aquatic organisms.

EPA’s first phase of test results, released on June 30th, indicated that none of the eight dispersants displayed biologically significant endocrine disrupting activity. While the dispersant products alone – not mixed with oil - are roughly the same, 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.

EPA believes dispersants should only be used sparingly and when absolutely necessary. Since the well was capped, only 200 gallons of dispersant have been applied to the Gulf, but constant monitoring continues. The results of the two phases of tests are helping to inform the Administration as the Federal Response Team evaluates the Congressionally-legislated oil spill response practices for future scenarios.

September update to the toxicity testing

EPA's results from the oil-only test for small fish in the second round of dispersant testing were inconclusive. EPA has repeated the tests and has updated the report to include the acute toxicity of Louisiana sweet crude to the inland silverside fish, Menidia beryllina, and includes the second phase of reference toxicant testing conducted with both Menidia and the mysid shrimp, Americamysis bahia (see page 13, Table 3, for new results).

The additional data are consistent with the original findings of the second round of dispersant testing. They show Louisiana Sweet Crude Oil alone to be more toxic to the silverside fish than the eight dispersants alone, as also indicated by the mysid tests. Additionally, the oil alone had similar toxicity to the silverside fish as the dispersant-oil mixtures, with the exception of the mixture of Dispersit SPC 1000 and Nokomis 3-AA, which were found to be more toxic than oil alone.

EPA will continue to update this page as additional data become available.

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Full reports on these tests can be found here:

Report
- Updated report - September, 2010: Comparative Toxicity of Louisiana Sweet Crude Oil (LSC) and Chemically Dispersed LSC to Two Gulf of Mexico Aquatic Test Species (PDF) (13 pp 121K)
- August, 2010: Comparative Toxicity of Louisiana Sweet Crude Oil (LSC) and Chemically Dispersed LSC to Two Gulf of Mexico Aquatic Test Species (PDF) (13pp 120K)
Press release
Questions and Answers on Dispersants Toxicity Testing (PDF) (7pp 16K)
Statement by EPA Assistant Administrator Paul T. Anastas (7pp 16K)
Audio of August 2 press conference call with EPA Assistant Administrator Paul T. Anastas, EPA's second round of independent dispersant testing.

(MP3, 37:38, 8.6MB) Download audio | Download transcript (PDF) (16pp., 40K)

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June 30 - Results of the Phase I Testing

Following BP’s response to EPA's directive – and to ensure that decisions about ongoing dispersant use in the Gulf of Mexico are grounded in the best available science – EPA began its own scientific testing of eight dispersant products on the National Contingency Plan Product Schedule (NCP-PS). 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 eight oil dispersants.

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.

While this is important information to have, additional testing is needed to further inform the use of dispersants. 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.

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more.

Full reports on these tests can be found here: