BP is celebrating the success of its top kill or “static kill” and is in the process of doing the same with a bottom kill once the relief well is fully functional to permanently seal the Macondo well in the Gulf of Mexico. The unseen but real kill in the Gulf however is the toxic dispersant Corexit that has been used on a large and unprecedented scale and will forever be remembered as the “final kill”.
BP, in collaboration with the EPA and the Coast Guard, has dispersed 2 million gallons of one the most toxic dispersants ever made: Corexit9500A and/or Corexit9527A.
The chemical structure of Corexit
The dispersant Corexit, manufactured by Nalco Holding Co, consists primarily of 2-butanol-ethylene and is not water soluble in itself. In order for the product to be effective as a surface spray, the manufacturer attaches two separate esters to the primary component.
The result is that when the spray comes in contact with the water/oil surface that the esters dissolve and the toxic compound can attach itself to the oil. The chemical breaks down the oil spill into small particles and makes the mixture sink to the bottom of the ocean so it can biodegrade over time.
The role of the EPA
The Environmental Protection Agency is responsible for maintaining a list of active dispersants in case of an oil spill or disaster and did approve the use of Corexit in addition to many other available dispersants such as JD2000, also known as Dispersit.
In the immediate aftermath of the Deepwater Horizon collapse, the agency gave permission to BP to start using Corexit as a dispersant.
On May 19, the EPA send a directive to BP executives and the Coast Guard with the request to use a less toxic but EPA approved dispersant instead.
The BP response was swift and very clear: since the Company used a chemical that was approved by the Agency, they would continue to use Corexit as the dispersant of choice given its efficiency and its availability.
In early June, Lisa Jackson, EPA Administrator, instructed BP and the Coast Guard to limit the daily use of Corexit to 3,900 gallons and further advised that if higher daily amounts were needed that such would have to be approved by the Agency on a case by case basis only.
Several daily requests for an increase of the allowed daily use were filed with the EPA, by Ret. Adm. Thad Allen starting in the first week of June, and all requests were granted and approved “pro forma”, resulting in a daily use of 10,000 to 36,000 gallons or 3 to 8 times the previously recommended volume.
The efficiency ratings of chemical dispersants
According to safety reports from Nalco Holding Co. and the EPA, the efficiency of three approved dispersants when used as a water surface spray is:
-Corexit9500A: 54%
-Corexit9527A: 62%
-Dispersit: 100%
Besides the difference in proven efficiency it also warrants to note that the only non-toxic dispersant is JD2000 or Dispersit. This puts into question why BP was so adamant in using a highly toxic chemical compound with a lesser efficiency rating.
Tomorrow we will continue this article and analyze the toxicity of Corexit mixed with oil and what the impact is on human life, through direct contact or inhalation, and the future of maritime life in the Gulf of Mexico.
Written by Nick Doms © 2010, all rights reserved
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