Coast Guard workers spray Corexit in a 2007 Berkeley, California, cleanup. It is not yet being used on Gulf of Mexico beaches. (U.S. Coast Guard photo)We finally know the main two dispersants that BP and the U.S. government are using to treat the ongoing Gulf spill. Both, by their maker’s own admission, have the “potential to bioconcentrate,” and both have “moderate toxicity to early life stages of fish, crustaceans, and mollusks,” according to a study by Exxon, the company that originally developed them. Their use may be the least-bad course, given the importance of minimizing oil’s effect on coastal wetlands. But a little digging into the chemical makeup of these two substances, which are being dumped in vast quantities into the Gulf, reveals that they could potentially do far more harm than good, both to the Gulf and to humans who later eat from it.