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Does the EPA know what it’s doing when it comes to dispersants?

The views expressed are those of the author and are not necessarily those of Scientific American.

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aerial-dispersant-applicationThe U.S. Environmental Protection Agency (EPA) has struggled in the past two months to come to grips with dispersants, the chemical cocktails being used to break up the Gulf of Mexico oil spill into tiny droplets that are easier for microbes to eat. It now appears that the EPA failed to require adequate controls for dispersant toxicity testing, despite the fact that the agency set very explicit criteria for how such chemicals should be tested. This follows the agency’s call for BP to use less deadly dispersants (pdf) with toxicities below a certain threshold when, in toxicology, it’s smaller figures that indicate a concentration that is more dangerous.

When testing a given chemical’s toxic impact, using the same methods on the same chemical—a so-called reference toxicant—should give consistent results no matter who carries out the tests. That way the toxicity of various products can be rated against each other, and against a certain benchmark. In addition to setting such a benchmark, the EPA also sets rules for how the chemical test solutions should be made, the concentrations required, and the organisms to be tested (in the case of dispersants, a fish, Menidia beryllina, and a shrimp, Mysidopsis bahia), among other specifications.

The reference toxicant provides scientific assurance that the tests were carried out in the manner intended, and helps to legitimize data that is, after all, provided by the makers of the chemicals themselves. In the case of the dispersants pre-approved for use by the EPA in the event of an oil spill, that reference toxicant is a surfactant called dodecyl sodium sulfate, a chemical that helps liquids spread out. Assuming all tests were carried out in a similar fashion, they should deliver similar results on the toxicity of SDS.

But toxicologist Carys Mitchelmore of the University of Maryland says that industry-provided testing values on the toxicity of SDS relative to various dispersants on the market vary “up to 300-fold.” The cause, she says: “They could have had bad water, bad animals, bad reference toxicant or they could have just run it badly.”

And NOKOMIS 3-F4 (purported by EPA’s list to be the least toxic dispersant) didn’t even use SDS as its reference toxicant, relying instead on copper sulfate. “That one’s the real outlier,” Mitchelmore says. As she testified to the U.S. Senate last week, “If you do not have consistent [lethal concentration data] for your reference toxicant then you cannot assume any of the other tests are reporting accurate data.”

That means the EPA does not know the relative toxicity of various dispersants available on the market and pre-approved for use, and never accurately knew their toxicity prior to the ongoing disaster in the Gulf of Mexico. So far, more than five million liters of dispersants have been used there. Which begs the question: Did anybody at EPA check the industry’s dispersant homework? “What does concern me is that there clearly is no quality control. How do they make the decision that these things are approved then?” Mitchelmore asks. “How could they have accepted this data?”

The agency is currently carrying out its own toxicity tests on the various dispersant options, an effort that should take no more than six weeks and could be done in as few as two. In the meantime, the impacts of the dispersed oil from BP’s Macondo well will provide answers. “We’re going to be filling in some of those data gaps,” Mitchelmore says, with data from the real world.

Image: A U.S. Air Force chemical dispersing C-130 aircraft from the 910th Airlift Wing at Youngstown-Warren Air Reserve Station, Ohio, drops an oil dispersing chemical into the Gulf of Mexico as part of the Deepwater Horizon Response effort, May 5, 2010. The 910th AW specializes in aerial spray and is the Department of Defense’s only large area fixed wing aerial spray unit. U.S. Air Force Photo by Tech. Sgt. Adrian Cadiz.

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  1. 1. hotblack 7:05 pm 06/22/2010

    Wow. Nice. Bad to worse. Why doesn’t BP just show up with machine guns and start mowing everybody down in the streets? It’d save them a lot of time if they’d just cut to the chase.

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  2. 2. quincykim 7:10 pm 06/22/2010

    Odd that the part of the Addendum specifying "toxicity value less than or equal to" when they should have said "greater than or equal to" did not raise a question mark right away. It hints at having been both issued and received by individuals without a hands-on knowledge of what the values mean.

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  3. 3. jerryd 8:33 pm 06/23/2010

    While they might be good for small spills, one this large it just makes things far worse. BP says they are safe, then mix it 10-1 with water and have them drink it. The only reason for it was to hide the true size of the spill.

    Facts are now it would be far better to just let the oil be on the surface so it can be collected and only kill surface life. With despersants you kill though out the water column.

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  4. 4. jack.123 11:22 pm 06/23/2010

    Wonder what Dawn and others like it are doing to our rivers and their flow into the oceans?

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  5. 5. tichead 11:06 pm 06/24/2010

    jack.123: I might prefer Dawn to the millions of gallons of toxic chemicals being sprayed now, not to mention the dispersant injection at the well head a mile down. As someone who once handled toxic chemicals, this stuff is average bad, not really bad. I don’t remember having to keep an MSDS (Material Safety Data Sheet) on file for Dawn. Up until about mid May this year the dispersant MSDS’s were available online at the manufacturer’s websites. Then they disappeared, you have to contact them some other way. Everybody runnin’ for the shadows…

    jerryd and quincykim: I couldn’t agree more. True, in large agreggated masses the oil floats. When broken into finer droplets the stuff becomes neutrally bouyant. So, does the dispersant dissociate from the oil once the smaller droplets form, or do they chemically react into some other perhaps more toxic goo? Or do the oil droplets simply stay contained in a shell of dispersant and float forever in the deep currents?

    And while I’m ranting and raving (seems to be alot of this going around), did anybody test the toxicity of the dispersent on the natuarally occuring oil devouring bacteria and microorganisms. Are the dumbnuts killing the very living things that could reduce the impact of this tragic catastrophe? A company in Sarasota, Florida manufactures oil eating bacteria, they have been using them to great effect for two decades. Why aren’t the folks on the front line spraying these wonderful bugs on the oil instead?

    hotblack: as a Gulf Coast resident, we’re hurtin’ even the oil hasn’t reach our beaches yet, but we’re still breathing. So I would prefer BP not go kinetic on the general populace. The chemical damage is more than enough already.

    In a more general sense, our government has completely failed us on this. The MMS failed to prevent it in ways to numerous for this post, the EPA couldn’t define an LD50 if it was crawling up their ‘face’, and no one, not one dangbean bureaucrat or politician or even BP themselves had a ‘Plan B’ for one of the riskiest ventures that we humans are so inclined to engage. I only hope the Atomic Energy Commission is watching all this and suffering a serious case of bunched up shorts.

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  6. 6. mervyn 12:57 am 06/29/2010

    Hi, why is it that nowhere is there any mention of the cumulative effect of the more than 100 major oil spill on the diatoms in the oceans. Taken together with the toxins being dumped in our oceans. The diatoms produce the majority of the oxygen for us to breathe. The late Lloyd Berkner from NASA in 1968 contended that it would onlh take a small number of major spills in the worng places at the wrong time to trigger an Extinction Level Event (ELE) and it could happen overnight. visit for possible solutions, Mervyn K. Vogt

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  7. 7. mervyn 1:09 am 06/29/2010

    Hi, One thing I would like to know is in the whole of this oil spill matter there has not been one word about the effect of the spill on the diatoms in the ocean. These microscopic organisms provide more than half of the oxygen we have to breathe. When the Torrey Canyon went down in1968 in the North Sea Lloyd Berkner from NASA stated that it would only take a small number of such incidents in the wrong time at the wrong place to trigger an Extinction Level Event(ELE), and that it could happen almost overnight. The Torrey Canyon carried 120,000 tons of oil. So far the Present spill has spread an estimated 70 million tons. Add to this the toxic chemicals and start to worry. Worry even more when you put this together with the more than 100 major spills to date that most have not heard of and then yoou can really worry. Visit for a start to some solutions
    Mervyn K. Vogt ps guess which corporation was concerned with the Torry Canyon……. you guessed it BP

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