Corexit Dispersant: An Experiment in the Gulf

September 1st – 5:18PM(CST)


Crude oil in salt water with Corexit 9500A dispersant

New Orleans, LA – The use of the chemical dispersant Corexit has been one of the major tactics employed since millions of gallons of crude oil were sent billowing into the open ocean on April 2oth.  Corexit’s use has been a source of much attention and debate, and yet the public remains largely in the dark as to the hazards it potentially poses.  Produced by the Nalco Holding Company, which has ties to both BP and Exxon, upwards of 2,000,000 gallons of the substances Corexit 9527A and 9500A have been used, on the surface and underwater, in the Gulf since April 20th (9527A was used initially , before being deemed too toxic by the EPA in late April).

While the scope of this disaster may be unprecedented, oil spills are not, nor is the use of dispersants to combat them.  In response to the 1989 Exxon Valdez spill, Corexit 9580 was tested to disperse the oil that had spilled into Prince William Sound, Alaska.  Years later, many of the cleanup workers from that spill are dead or suffering from a host of nervous-system, liver, and kidney diseases related to the toxic substances found in Corexit and crude oil.  Given the history of these substances and the threat they pose, the lack of public disclosure is frightening.  The full list of ingredients and quantities in Corexit 9527A have not been made public by Nalco and the company has protected this information about Corexit 9500A, which was the main substance used, by claiming it as a trade secret.  Not until June did they hand over this information to the EPA.  What Nalco does openly state is that no studies have been done regarding the toxicity of Corexit 9500A, which you can read in the product’s Manufacturer Safety Data Sheet.

Crude oil in salt water at a lab in Worcester, Massachusetts

Both substances are deemed hazardous by the EPA, with potential acute hazard towards red blood cells, the kidney, and liver, among others.  Not only does Corexit pose a threat as a toxic substance, but some information suggests that its combination with crude oil results in an even more toxic substance than either would alone.  Because dispersants work by breaking up thicker patches of oil into smaller droplets, much of the resulting oil becomes suspended in the water column, rather than floating on top as thick crude will.  Not only does this render the oil more difficult to clean up, but it poses a significantly greater risk to marine life that lives below the surface.  According to a recent study, the exposure of crude oil to Corexit 9500A raises the levels of some toxic substances by as much as 35 times.  Rather than having a thick, and highly visible, layer of crude sitting on the ocean surface, the use of dispersant takes oil off of the surface and dissolves it throughout the ocean.  Corexit does a great job of getting oil out of the public eye, but the cost paid by everything below the surface and those cleaning it will likely be even more significant because of the decision to use it.

-Nicholas Stone Schearer

Watch a video about dispersants here and watch the full video of the experiment here.


  1. How can you get this message out – it is such a powerful story

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