As we all know, on May 20, the EPA called on BP to use a less harmful dispersant to dissolve the oil gushing into the Gulf of Mexico. According to a notes from a May 27 meeting (PDF) on the long-term impact of dispersants on the Gulf ecosystem, the dispersants are less harmful than simply allowing the oil to wash up on shore, but “much is unknown about the long term environmental impacts of dispersants when used in unprecedented volume and in the subsea.” That means that we don’t know how effective dispersants are when used underwater.
But what do dispersants actually do? And how exactly are they damaging to ecosystems? Popular Science has a great write-up of how oil dispersants work—and what their true impact could be.
What are dispersants?
According to Popular Science, “Corexit, the dispersant BP is currently using, contains six chemicals. The exact recipe is a secret, according to Corexit’s manufacturer, Nalco, but it contains a surfactant and a solvent. Surfactants are long molecules that are hydrophilic (water-seeking) on one end and oleophilic (oil-seeking) on the other. One end grabs an oil molecule, the other, a water molecule. By reaching across the oil-water boundary, the surfactant lowers the tension that keeps the two substances separate.”
Basically, a dispersant breaks oil up into smaller bubbles so that bacteria in the water can dissolve it faster than it would be able to if the oil were in a large clump. There is some concern that Corexit is less effective and more dangerous than other dispersants. Little is known about the “secret ingredients” in Corexit, but there is a petition to change that, should you wish to sign on.
What kind of impact do they have?
According to Popular Science, “Dispersants have never been applied on this scale, leaving environmental scientists guessing about the consequences. Corexit may have caused seven cleanup workers to be admitted to the hospital with shortness of breath and nausea.”
Of course there are also concerns regarding the impact of dispersants on wildlife and undersea plants. According to this study, when applied in small amounts to Mallard eggs, Corexit is as fatal as raw crude oil.
Image courtesy of Flickr user Deepwater Horizon Response.