The Environmental Protection Agency says a new study shows that dispersants used to break up oil in the Gulf of Mexico are no more toxic to aquatic life than oil alone.

The EPA says the tests also show that when mixed with oil, the dispersant used in the Gulf, Corexit 9500A, is no more or less toxic than oil mixtures with available alternative chemicals.

The test results were released Monday as the Obama administration defends itself against assertions that officials allowed oil giant BP to use excessive amounts of chemical dispersants whose threat to sea life remains unknown. Congressional investigators say the Coast Guard routinely approved BP requests to use thousands of gallons of Corexit despite a federal directive to use the chemical sparingly.