More proof that toxic dispersant and oil spills don’t mix


This has become a familiar storyline: Another month, and another study showing that the kind of toxic dispersant that was dumped so indiscriminately in the Gulf of Mexico in the weeks immediately after the Deepwater Horizon catastrophe poses a significant threat to the long-term health of marine life.

This latest study deserves particularly close attention, because of the rigorous scientific controls comparing the effect of using a dispersant to the impact of just the oil itself:

Treating oil spills at sea with chemical dispersants is detrimental to European sea bass. A new study, to be presented at the Society for Experimental Biology meeting in Valencia on July 6, suggests that although chemical dispersants may reduce problems for surface animals, the increased contamination under the water reduces the ability for fish and other organisms to cope with subsequent environmental challenges.

A team of researchers headed by Prof Guy Claireaux at the University of Brest in France looked for the first time at the effects of chemically dispersed oil on the performance of European seabass to subsequent environmental challenges.

The researchers designed swimming challenge tests in an ‘aquatic treadmill’, similar to the tests used in human medicine for health diagnosis. They analysed European seabass’ maximum swimming performance, hypoxia tolerance and thermal sensitivity as markers for their capabilities to face natural contingencies. They then exposed the fish to untreated oil, chemically dispersed oil or dispersant alone for 48 hours. During the following 6 weeks they measured individual growth and then once again analysed the seabass’ performance in the swimming challenge tests.

Oil exposure impacted the ability of fish to face increased temperature, reduced oxygen availability or to swim against a current and these effects were further aggravated with the addition of the dispersant. The dispersant alone had no effect on the ability of fish to face the challenge tests.

Since 2010, I’ve seen first-hand the severe health impact on several divers who went down into the BP oil spill after a couple million gallons of Corexit, a highly toxic dispersant, was deployed in the waters. But although it’s been suspected for a while that dispersant both made people sick and damaged the marine environment, it’s been just in the last year that studies such as this one that have confirmed our worst fears about the substance.  In April, the journalist Mark Hertsgaard reported in Newsweek that warnings about the risks and the proper use of Corexit, manufactured by Nalco, were ignored in the BP spill.

The problem is that — as this new French study clearly shows — dispersant is good at a) making an oil disappear from view and b) reducing some of the more obvious health risks to humans and other creatures on the surface. But when mixed with oil, this hazardous chemical poses a much greater threat in the water column, to a much wider array of species. Unfortunately, we can’t undo the damage done to the Gulf in 2010. But knowing what we know now, why would we ever use dispersant in an oil spill again?

To learn more about the research on dispersant recently carried out in France, please read:

For more of Mark Hertsgaard’s reporting from Newsweek about the hazard of Corexit, check out:

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Stuart H. Smith is an attorney based in New Orleans fighting major oil companies and other polluters.
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