FILE -This June 3, 2010 file image from video provided by BP PLC shows oil dispersant being applied at the oil leak in the Gulf of Mexico. The white wand in the center is releasing the dispersant. The first peer-reviewed study looking at the effectiveness of chemical dispersants used deep undersea on the BP oil spill found mixed results. It appeared to keep some oil from bubbling up to the surface where it could do worse damage, but it didn't appear to biodegrade the oil quite as fast as promised. (AP Photo/BP PLC, File)

FILE -This June 3, 2010 file image from video provided by BP PLC shows oil dispersant being applied at the oil leak in the Gulf of Mexico. The white wand in the center is releasing the dispersant. The first peer-reviewed study looking at the effectiveness of chemical dispersants used deep undersea on the BP oil spill found mixed results. It appeared to keep some oil from bubbling up to the surface where it could do worse damage, but it didn't appear to biodegrade the oil quite as fast as promised. (AP Photo/BP PLC, File)