Testing has found that eight dispersants, including one used in combating the Gulf of Mexico oil disaster, are no more toxic when mixed with oil than the oil alone, the Environmental Protection Agency said Monday.

The tests prove that the oil itself, not the dispersants, is "enemy No. 1," Paul Anastas, EPA assistant administrator for research and development, told reporters on a conference call.

Use of the dispersants to break up oil after the April 20 Deepwater Horizon rig explosion sent millions of gallons of crude gushing into the Gulf has been a controversial topic.

Testing was done on sensitive marine species in their juvenile life stage, when they are at their most sensitive, Anastas said. During tests, researchers increased the concentration of the dispersant, mixed with Louisiana sweet crude oil, to concentrations even higher than that species are expected to encounter in the Gulf, Anastas said.

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