But according to EPA data, Corexit ranks far above dispersants made by competitors in toxicity and far below them in effectiveness in handling southern Louisiana crude.
Of 18 dispersants whose use EPA has approved, 12 were found to be more effective on southern Louisiana crude than Corexit, EPA data show. Two of the 12 were found to be 100 percent effective on Gulf of Mexico crude, while the two Corexit products rated 56 percent and 63 percent effective, respectively. The toxicity of the 12 was shown to be either comparable to the Corexit line or, in some cases, 10 or 20 times less, according to EPA."
Climate Progress’ Joe Romm notes that as toxic as Corexit is, dispersed oil is more toxic.
Out of Sight: BP’s dispersants are toxic — but not as toxic as dispersed oil
Plus the threat the disaster poses to America's primary coral reef
Chemically dispersing oil spills “solves the political problem of visible oil but not the environmental problem,” Robert Brulle, a 20-year Coast Guard veteran and an affiliate professor of public health at Drexel University, told me. These dispersants “do not actually reduce the total amount of oil entering the environment,” as a 2005 National Academy of Sciences report on the subject put it.
In short: out of sight, out of mind. But not out of the body of marine life.
Dispersants decrease the amount of oil that directly reaches the shores or the creatures that live on the shores or sea surface. But they increase the exposure to oil by creatures that live in the water or on the sea floor — like, say, shrimp or oysters.