MTorrice writes "During the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, clean up crews applied millions of liters of dispersants to break up the oil. At the time, the public and some scientists worried about the environmental effects of the chemicals, in particular how long they would last in the deep sea. According to a new Environmental Protection Agency study, the key active ingredient in the dispersants degrades very rapidly under conditions similar to those found at the Gulf surface during the spill. Meanwhile, in the much colder temperatures found in the deep sea, the breakdown is quite slow. The chemicals' persistence at deep-sea and Arctic temperatures suggests more research is needed on their toxicity, the researchers say."