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5 December 2013 11:26 am ,
Vol. 342 ,
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Oil Dispersant Study Released by EPA, But Big Questions Remain
30 June 2010 5:36 pm
The Environmental Protection Agency released data today from its first round of toxicity testing on dispersants that could be used on the oil spill in the Gulf of Mexico, but the agency's chief scientist said that not enough was yet known to make a recommendation about which one is best to use.
Since the spill began, almost 1.6 million gallons of dispersant have been sprayed onto the water and released at the site of the leaking well. Dispersants break up the oil into smaller droplets, which break down faster and are less likely to coat birds or damage wetlands. But the dispersants themselves can be toxic to other marine life, such as shrimp and fish.
BP has been using a dispersant called Corexit 9500, which appeared to be particularly toxic. On 20 May, EPA asked BP to find a less toxic alternative. When BP said it couldn't find a safer substitute, EPA began to test eight of the 14 dispersants that it had previously approved for oil spills. These tests aren't entirely new: Companies must submit toxicity data when they request approval for dispersants, but variation in methods made it difficult to compare the results. In addition, the existing tests looked at a mixture of dispersants and fuel oil, not the crude oil now gushing into the gulf.
EPA's National Health and Environmental Effects Research Laboratory supervised acute toxicity on two species native to the gulf: a small fish, Menidia beryllina, and mysid shrimp, Americamysis bahia. Corexit 9500 and seven other dispersants are all about equally toxic, with some slightly more toxic to fish and others more toxic to shrimp. Ranging from the category of "practically non-toxic" to "slightly toxic," all the dispersants are less toxic than oil, said Paul Anastas, EPA's chief scientist, at a teleconference about the results.
However, experts say that the combination of dispersant and oil can be more toxic than either alone. EPA is testing these mixtures, and Anastas says he expects results within the next few weeks. Only after considering these further data will EPA consider whether to order BP to change its use of dispersants. (The average daily amount used has dropped by 68% since 23 May, when EPA told BP to lower the volumes.)
Another important question is the risk of chronic effects, such as reproductive harm, from exposure to dispersants over the weeks to months they take to degrade, says Carys Mitchelmore, environmental toxicologist at the University of Maryland's Center for Environmental Science in Solomons. It's not clear whether EPA plans to do this. Perhaps the biggest problem with dispersants, Mitchelmore points out, is that they allow droplets of oil to reach organisms below the surface that otherwise wouldn't have been exposed.