As we’ve reported, Corexit was also used after the Exxon Valdez disaster  and was later linked with human health problems including respiratory, nervous system, liver, kidney and blood disorders. One of the two Corexit products also contains a compound that, in high doses, is associated with headaches, vomiting and reproductive problems .
Given that the dispersants are EPA-approved, the choice of which ones to use was left to BP, which had stockpiled large amounts of Corexit and is now ordering more.
BP has defended its choice to use Corexit. A BP spokesman called the product  “pretty effective,” and said it had been “rigorously tested.” It is not testing other dispersants, he said,  because it’s focusing on stopping the spill. Mani Ramesh, the chief technology officer for Nalco, which makes Corexit, disputed claims that the product is harmful to the environment , telling Reuters that Corexit’s active ingredient is “an emulsifier also found in ice cream.”
Dispersants like Corexit break up oil into droplets that linger longer in the water instead of collecting at the surface. The choice to use them is inherently an environmental tradeoff. Their use in the Gulf spill has limited the instances—and images—of oil-covered seabirds, but has kept the effects of the spill mostly underwater. Scientists have discovered giant plumes of dispersed oil  in the deep waters of the Gulf, though the EPA has said “there is no information currently available ” to link the dispersants to those deep-sea plumes. The plumes are now fast approaching the Gulf loop current , which could spread the oil into the Atlantic Ocean. (read the whole thing)
Also, it turns out that BP owns the company that makes Corexit, so no wonder they don't have time to test or try anything less toxic. Fishermen and brown people, meanwhile, trying to help clean up the mess, are collapsing and getting sick, just like the last time BP's company profited by using Corexit on the Exxon Valez spill.