Friday, May 7, 2010

A toxic cleanup

The first rule of working as an undergrad in my lab is wash your hands before putting your hands in the fish tanks. And never, NEVER, ever, wash your hands or any glassware with soap.Soap, a surfactant, is highly toxic to aquatic organisms. So good thing we’re dumping tons of it in the Gulf, right?

Oil spills are really nasty environmental disasters. One of the main reasons being, as much as it kills anyone to say, sometimes the best remediation effort is to do nothing at all. This was true for example in the Exxon-Valdez spill where to clean the coast of oil, clean up workers used high powered hoses and blasted the rocks with scalding hot water. Sure, it made the rocks on the surface clean, but it actually drove the oil deeper below the surface, into the crevices of the rocks and sands where it could not be broken down by sunlight. In addition, the hot water killed any coastal flora and fauna living on the rocks and also destroyed the bacteria that would degrade the oil. This is but one example where the remediation effort actually worsened the environmental state after an oil spill.

Another example is the use of dispersants. If used properly they are an effective way of reducing the size of an oil slick. The dispersant which contains surfactants, bind to the oil and form little tiny globs that sink from the surface.By breaking the slick into smaller units, or in this case, billions of tiny oil blobs, there is more surface area per volume for bacteria to breakdown the oil and also further aids the spilt and dispersal in the water by wave action. But there comes a cost, these chemicals are toxic, and should never be used in very near shore environments (100m). The risk of it washing on shore and poisoning the coastal ecosystem is too great.

But what if the slick we’re using it on is moving closer and closer to the coast? The Gulf oil spill is by no means small and dispersants have not been used before on a spill of this magnitude. The NYT reports that so far 160,000 gallons of dispersants have been used on the surface and another 6,000 gallons below. The main chemical being used is Corexit.What are the active ingredients in Corexit? Wish I could tell you.It’s a trade secret and since its under a proprietary name like, Coca-Cola, they don’t need to tell you what’s in their product.Hmm…ok then. Well is it safe at least? No, says the British government, which denied approval for its use because it was found to be toxic to coastal invertebrates. Nalco, the company that manufactures Corexit, has released a 10 page report which lists the health hazards of their product which states it can cause skin and lung damage on contact and poses a “moderate” environmental risk.

There’s a 230,000 gallons of Corexit on tap and further production has been commissioned by BP. Wired reports though that a safer alternative is available but not being used. Dispersit was tested against Corexit by the EPA and while Corexit could breakdown Gulf crude oil 54% of the time, Dispersit had a 100% success rate. That alone seems like a good reason to switch, but what about toxicity? Using both a vertebrate (silver fish) and invertebrate (shrimp) model organism, both dispersants were also tested.Corexit was 3x more lethal to fish and 2x as lethal to shrimp compared to Dispersit. I’m guessing this is not the news Gulf fishermen and shrimpers want to hear.

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