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The BP Oil Spill: Responsive Science Supports Emergency Response

EPA scientists provided key support for the federal response to the Deepwater Horizon oil spill.

Three people on a boat deck observe the fires from Deep Horizon in the distance.

In April 2010, the offshore mobile drilling unit Deepwater Horizon in the Gulf of Mexico caught fire and collapsed, killing 11 crew members and injuring 17 others. As the platform sank to the ocean floor, the untapped well began to spew millions of gallons of crude oil directly into the Gulf.

Within days, it became clear that a massive response was needed to meet the challenges brought on by the unfolding crisis.

President Barack Obama declared "my administration will continue to use every single available resource Exit EPA Disclaimer at our disposal" to address the incident and help the Gulf and local communities facing what would turn out to be the worst oil spill in U.S. history.

The expertise of EPA scientists was among the first of those federal resources to join the effort. The EPA provided full support to the U.S. Coast Guard, the lead for coordinating response, containment, and remediation activities.

Cleanup and mitigation activities were immediately aimed at minimizing known threats to coastal wetlands, wildlife, fisheries, and other environmental resources. Such activities included booming and skimming operations, burning surface oil, and applying dispersants to break up oil, both on the surface and in the deep waters where the oil was flowing.

Dispersants have properties that break down oil, helping to prevent thick, sticky crude from fouling beaches, coating seabirds and other aquatic wildlife, or reaching ecologically sensitive coastal wetlands. Breaking the oil down into smaller droplets also promotes natural biodegradation by tiny, oil-consuming marine microbes.

But the use of dispersants in the Gulf garnered considerable public debate. Concerns primarily centered around unknowns about the toxicity of dispersants for people and aquatic organisms, especially considering the massive quantities that were called for in the Gulf of Mexico.

In the midst of the ongoing Gulf crisis, EPA scientists were called on to provide key scientific information to help inform decisions about the use of dispersants.

ToxCast Delivers
Toxcast machine

Thanks to EPA's ToxCastTM program, dispersant toxicity testing during the Gulf Oil crisis included the use of automated, high-throughput screening assays that allowed researchers to quickly test complex chemical mixtures.

Launched in 2007, ToxCast involves the use of innovative computational technology methods to development fast and efficient ways to advance toxicology research.

"The in vitro tests used in this study rapidly profiled the complex dispersant formulations without the use of animals, and screened for potential endocrine activity, other end points, and cytotoxicity. In different circumstances, a similar rapid screening effort could be used to make time-sensitive decisions based on potential hazard and risk," concluded EPA scientists in the scientific journal Environmental Science & Technology.

(Citation: Analysis of Eight Oil Spill Dispersants Using Rapid, In Vitro Tests for Endocrine and Other Biological Activity; Richard S. Judson, Matthew T. Martin, David M. Reif, Keith A. Houck, Thomas B. Knudsen, Daniel M. Rotroff, Menghang Xia, Srilatha Sakamuru, Ruili Huang, Paul Shinn, Christopher P. Austin, Robert J. Kavlock, and David J. Dix. Environmental Science & Technology: 2010 44 (15), 5979-5985)

EPA scientists conducted a series of tests on eight commercial dispersants, including Corexit 9500, BP's dispersant of choice for cleanup operations.

The first phase of EPA's testing focused on assessing the acute toxicity of dispersants alone (not mixed with oil). Tests were conducted on larval stages of two aquatic species representative of organisms found in the Gulf of Mexico: mysid shrimp (Americamysis bahia) and inland silverside fish (Menidia beryllina).

Additionally, more than 80 in vitro tests from EPA's computational toxicology and endocrine disruptor research programs were used to rapidly screen the dispersants for endocrine activity and cytotoxicity (cell death). This work was conducted under the Agency's collaborative ToxCast program, which taps innovative technologies—including automated, high-throughput screen techniques—to conduct fast, efficient assay and screening tests.

Results from the first phase of testing, released June 30, 2010, indicated that all eight dispersants had roughly the same toxicity, and all fell into the "practically non-toxic" or "slightly toxic" category. Scientists found that none of the eight dispersants displayed endocrine-disrupting activity of "biological significance."

During a second phase of testing, researchers assessed the acute toxicity of multiple concentrations of Louisiana Sweet Crude (LSC) oil alone and in combination with each of the eight dispersants. Results, released on August 2, 2010, indicated that the toxicities of the eight dispersants mixed with oil were roughly similar to one another. Of particular interest to clean up operations, was the conclusion that dispersant-oil mixtures were generally no more toxic to the aquatic test species than oil alone.

The entire process from the initial request to test dispersants to the full report on the dispersants' toxicity took six weeks. This meant that ongoing decisions and activities in the Gulf could be based on science and robust toxicity testing.

Making decisions during a crisis is always a challenge, but EPA's research provided response operations with the scientific information needed to make tough calls about the use of dispersants.

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