Scientists: Efforts to disperse the BP spill made it much, much more toxic


One of the least understood aspects of the environmental devastation caused by the Deepwater Horizon rig explosion and spill in 2010 is the role of the chemical dispersant — known by its brand name Corexit — that was deployed by BP and its contractors, with the enthusiastic support of federal regulators, in the weeks that oil flowed freely into the Gulf of Mexico.

Spraying Corexit made some of the oil disappear from sight — which we all know was the No. 1 priority in the spring of 2010 for the image-conscious BP — but at a tremendous cost to the marine environment. From Day One, our experts told us that the widespread use of Corexit had unknown — but quite possibly severe — consequences for the food chain in the Gulf of Mexico.

On May 11, 2010, I noted in a statement that the “Corexit 9500” dispersant was designed to breakup the slick at the water’s surface, sending the oil into the water column, and from there, to the bottom of the seabed where bottom residing organisms such as shrimp, crabs and oysters reside. My concern with the usage of such dispersants at that time was that, aside from being themselves toxic, they do little more than hide the problem. Many leading experts, doctors and environmentalists had discredited the use of Corexit as a tool for oil spill clean up. As another lawyer observed at that time:

“Toxicity of the petroleum products is increased when it is dissolved into the water by dispersants,” said Co-Counsel Robert McKee, Gulf Oil Disaster Recovery Group. “In essence, this activity is making aquatic organisms more exposed to chemicals’ harm. The attempt to make these floating tars and oils disappear from view by the use of dispersants increases the likelihood of poisonous effects in these oil polluted waters.” 

Also, Marco Kaltofen, an outstanding environmentalist and civil engineer with whom I’ve worked closely on the Deepwater Horizon spill as well as other issues, produced an outstanding video in 2010 showing the toxicity of Corexit. You can watch it here.

In other words, the dangerous impact of Corexit was well known. In the end, it appears that a whopping 2 million gallons of the dispersant were sprayed in the Gulf; in other words, authorities responded to a horrendous oil spill by dumping a hazardous chemical — an appalling situation. The question lingered: Just how damaging was its widespread use in 2010?

Now, scientists from Georgia Tech and from Mexico are here to report that Corexit was even more poisonous than we imagined:

A new study by researchers at the Georgia Institute of Technology and the Universidad Autonoma de Aguascalientes in Mexico finds that mixing oil with dispersant made the BP oil spill worse. Georgia Tech reports that the two million gallons of dispersant used to clean up the 4.9 million barrels of oil that spilled into the Gulf of Mexico during the 2010 Deep Water Horizon spill made the oil 52 times more toxic.

The researchers discovered that mixing the dispersant with oil raised the toxicity of the mixture up to 52-fold over the oil alone. They found that the mixture’s impacts increased the death rate of rotifers, a microscopic grazing animal at the base of the Gulf’s food web.

Combining oil from the BP oil spill and Corexit, which is the dispersant mandated by the Environmental Protection Agency for clean up, the researchers measured the toxicity of oil, dispersant, and mixtures on five strains of rotifers.  Rotifers are often used by ecotoxicologists to calculate toxicity in marine waters because of their fast response time, ease of use in tests and sensitivity to toxicants.

Not only did the oil-dispersant mixture increase mortality in adult rotifers, as little as 2.6 percent of the mixture decreased rotifer egg hatching by 50 percent. These eggs hatch into rotifers each spring, reproduce in the water column and provide food for baby fish, shrimp and crabs.

 And this is not the only new bad news on the Corexit front. A second study has found that while Corexit may have “dispersed” the oil from the surface, it also allowed oil to penetrate Gulf beaches more deeply:

Their findings: Corexit 9500A allows crude oil components to penetrate faster and deeper into permeable saturated sands where the absence of oxygen may slow degradation and extend the lifespan of potentially harmful polycyclic aromatic hydrocarbons (PAHs), a.k.a. organic pollutants—a.k.a. persistently abominable hork—in the marine environment.

Furthermore, the authors warn, dispersants used in nearshore oil spills might penetrate deeply enough into saturated sands to threaten groundwater supplies. (Did anyone look at this in the BP settlement?)

Which is exactly the point I was trying to make earlier this fall when I argued that the proposed $7.8 billion BP settlement with Gulf residents and business owners was a rush to judgment. That’s because there is so much more to learn about the 2010 spill and the long-term calamitous effect that it continues to have on the region and will likely have for years to come.

This is not some abstract academic debate: Every day, those of us who live on the Gulf Coast are very aware of the massive and highly toxic mistake that was made by deploying Corexit — the cleanup workers who were sickened by exposure, the dead zones that were once thriving oyster beds and fisheries. While there’s some relief in the large criminal and expected civil penalties assessed against BP right now, we should remember what a colossal mistake was made in the decision to massively deploy Corexit, and how all that damage is still not yet known.

To read the May 11, 2010, warning about Corexit from me and from other scientists and environmental attorneys, please read:

To watch a video from civil engineer Marco Kaltofen showing the toxicity of Corexit, go to:

To read more about the new research on Corexit toxicity from scientists in Georgia and Mexico, please read:

To read a Mother Jones report on the second study on Corexit’s impact on Gulf beaches, check out;

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Stuart H. Smith is an attorney based in New Orleans fighting major oil companies and other polluters.
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