Repost from 2011: UC Davis Environmental Toxicology Professor Breaks Down Why Dispersants Were Used

The following article originally was published on Examiner.com, August 10, 2011, a year and about a month after the Macondo well was capped. Since its publication, much research has been done on the effects of Corexit and petroleum in the Gulf, many of which can be accessed here.

Ron Tjeerdema, professor and chair of the UC Davis Department of Environmental Toxicology, has been a member of the scientific advisory panel to NOAA and BP on dispersant use in the Gulf of Mexico. Now he is a member of the US EPA Scientific Advisory Board's Oil Spill Strategy Review Panel, which is evaluating the agency's "Draft Oil Spill Research Strategy" to guide future research on spills.

Dr. Tjeerdema spoke to this reporter Friday about dispersant use in the Gulf, the chemistry of Corexit, and why sometimes hard choices have to be made. Following is an edited transcript of that conversation.

The Gulf community has been sharply critical of the way dispersants were applied after the oil spill. Do you concur that there is cause for concern? Why or why not?

I don’t think there's cause for concern. The problem with the Gulf spill was that it very quickly, because of the sheer size of the spill, the amount of oil coming out of the ground, it very quickly outgrew any other response capability in the Gulf. Because initially they did some booming….then burning and skimming. They did not have the resources to deal with it, so very early on it became an issue [of] there was only one thing left to do – let the oil come out unabated till they could eventually cap or they disperse. Unfortunately, that was the choice.

I view it as a shortcoming of the federal government and the oil industry. They were not prepared for this size of a blowout so it very quickly overwhelmed them. And so the choices were limited. I suspect that had they not dispersed, you’d be asking why they didn’t disperse. We will never know for sure [if this was the best choice because]…there wasn’t another well blowout [of this magnitude] that we could use as a comparison.

What is the EPA’s Draft Oil Spill Research Strategy? What have you evaluated so far?

It's not public information at this point. It’s known there is a scientific advisory panel. The EPA has a draft of the research they want to conduct in the future so they have asked us to take a look and give comments as to whether that’s a good direction to go in the future.

As it pertains to oil spills.

Yes. Without saying specifically what will be in it - it's [going to be] guidance for oil spill research in the future.

Do you have a quantity for me of how much dispersant was applied in the Gulf and are we only talking about Corexit or something more?

The best guest is 2 million gallons were applied to the Deepwater Horizon. Which is about 1 percent of the oil that came out. That is a 1 to 100 ratio, which is lower than would be applied [in some other situations]. Corexit is the main name of the dispersant used, but it included many other components. *

What are the health effects of this much dispersant? How does it affect people who say, travel up and down the shore every day for weeks on end?

Health effects depend upon amounts you are exposed to, and the more you are exposed to anything the more health effects you are likely to have. The vast majority of dispersants were applied at the well head 40 plus miles from the shore. People on the beach are not likely to have health effects. Dispersants are more likely to stay offshore in these clouds below the surface.

Explain what you mean by that.

What a dispersant does – it breaks oil into droplets. When you apply a dispersant to get oil off the surface of the water, if you apply a dispersant to that oil, instead of having this floating slick it breaks it up into a cloud of droplets 30 meters (98 feet) below the surface of the water, and droplets continually break up and dilute dispersants from there.

The idea is not only have you gotten the oil off the surface, you make more surface area for bacteria to digest the oil.

Microbes.

Yes. ###

UPDATE: 4-15-2017: As of today, the EPA claims that only 200 gallons of dispersant were used following the capping of the well. (Note, an earlier version of this blog today mistakenly said "the spill" rather than "the well". The original posting date was also incorrectly stated as 2010 instead of 2011, and that eight different dispersants were used. Eight dispersants were tested; Corexit was used. The writer regrets the errors.) Further, they say they are constantly monitoring the site, and testing of Corexit's effects has continued. For more information: https://archive.epa.gov/bpspill/web/html/dispersants-testing.html#phase2

* Prof. Tjeerdeema said the components in Corexit were a secret for a long time, not for any dubious reason but solely to protect against patent infringement from competitors. He pointed out that later the information became available on the EPA web site. The chemicals that make up the Corexit and the fact that the federal government kept this secret is a topic of concern and debate. Two main types were used: COREXIT 9500 and COREXIT 9527, which are essentially interchangeable. (The original story listed the chemicals used in Corexit; those chemicals can be accessed on EPA's website: https://archive.epa.gov/bpspill/web/html/#list.)

PHOTO: Wikimedia Commons Images.