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Many questions still unanswered on dispersants following EPA report

Lisa Suatoni

Posted August 4, 2010

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This week, the EPA released an additional round of research findings on the dispersant used in the Gulf Oil Spill.

The EPA has conducted acute toxicity testing of eight chemical oil dispersants - including the one used in response to the Gulf oil spill - on two aquatic test species which are found in the Gulf, a small mysid shrimp and a small fish, Menidia (neither are consumed by humans). 

The first round of EPA laboratory testing found that the dispersants were less toxic than the southern Louisiana crude itself and that they displayed similar toxicities to one another.  The second round of EPA testing found that the dispersant/oil mixtures had similar toxicities to southern Louisiana crude itself and similar toxicities to one another (with the exception of the dispersant brand Nokomis/oil mixture which was more toxic to the shrimp than oil alone).

These results represent another piece to a very complex puzzle. 

In a statement to the press about these research results, Dr. Paul Anastas said that ‘while more needs to be done, the picture is becoming clearer’ that dispersants were an ‘important tool in this response.’ 

Dr. Anastas pointed to four lines of evidence:

  1. the dispersants appeared to be helping keep oil off our shoreline (in other words, in the water)
  2. the dispersants are less toxic than the oil being released
  3. the dispersant/oil mixture has roughly the same toxicity as the oil itself  
  4. no traces of dispersant have been found ‘away’ from the well head

But while it may be tempting to conclude that the use of dispersants during this catastrophic oil spill was a good idea, we urge the federal government not to hasten this evaluation and rush to judgment.

The unprecedented and widespread application of dispersants in this oil spill was a grand experiment.  Given the scale of this spill, its position offshore, and the severe and long-lasting impacts of oil to salt marsh ecosystems, the rational was clear and defensible. 

However, as the most recent National Research Council panel on the topic concluded in 2005, much remains unknown about the efficacy and impacts of chemical dispersants.  And as a consequence, careful and thorough study of these factors is imperative. 

It would be unwise to draw conclusions about the safety of their use following these two laboratory experiments on toxicity (particularly when the results from phase II are not concordant with previous research on the topic) and field evidence that shows the dispersants were successfully dispersing the oil.

Many important pieces of the puzzle are outstanding:

  •  Where has the oil gone?  What proportion has hit land, sunk to the bottom, evaporated, or remains mixed into the water column?  This final calculus has not been conducted but is essential to understand the efficacy of the dispersants.
  • How did the chemical dispersion at 5000 feet depth differ from the physical dispersion at that depth that was happening naturally?
  • How large an area offshore is impacted?
  • What ocean organisms and ecosystems encountered the oil?  What harm has occurred and may occur long term?
  • Is the chemically dispersed oil – or the dispersants – getting into the food chain; is there the potential for it to get into the food chain?
  • What are the public health implications of exposure to dispersants by the response workers?
  • What are the public health implications for food consumption?

It is clear that the use of chemical dispersants is a tradeoff - but it’s not at all clear that we fully understand the tradeoff we made yet.  This question of tradeoffs represents a ‘500 piece’ puzzle and cannot be evaluated with four puzzle pieces.

We need federal scientists from NOAA as well as the EPA get to the bottom of the remaining questions.  It’s the follow-through that will make this catastrophe less of a disaster. 

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Mark ElliotAug 5 2010 02:22 AM

From the first report, the use of dispersants seemed to me to be a perceptual mitigation and little more. Especially as they were applied subsurface. The extent to which they were deployed - with no supporting research, of course - is to this day cause for concern.
That's why the recent reports of reduced toxicity in the Gulf are so patently unbelievable that even an observant Gulf fisherman told PBS he doesn't believe anything he's told by NOAA about the spill. The administration has a tough hill to climb on this one. If only officials weren't so heavy-handed. It reminds me of Todd-Whitman's infamous ground zero pronouncement. "The air is safe...."

Jim Bullis, Miastrada CompanyAug 9 2010 01:36 PM

Thanks for keeping on this.

Notice however that if the dispersant was equal to oil in toxicity, by adding dispersant in equal amounts as the oil, the spill toxicity was doubled.

Of course toxicity is only a part of this. The issue is more mechanical than chemical in nature. A plastic bag is not particularly toxic, but if placed over a person's head and tightened around his neck, that person might feel he was in danger.

Still, the real question is what happens on the deep ocean floor at 5000 ft where the vast majority of the sunken oil would go if it actually went to the bottom. The few living creatures at this depth will not be easy to represent in damage lawsuits.

I was surprised to see an eel like creature on the video stream, but no shrimp or other commercial seafood stock. Seriously, the ocean floor seems to be a likely escape for the perpetrators of this disaster.

The remaining issue is how much of the dispersed concoction remains as 'plumes' or just some other kind of blob that hangs in mid-depths and is thus likely to get picked up by the Gulf Stream or get slowly mixed upward and then acts as a long term plague on the Gulf Coast.

One more question is whether bacteria eats the dispersant as effectively as it eats oil.

Somehow the test by the EPA seems woefully naive about the danger here.

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