WASHINGTON (Reuters) - Dispersant chemicals used to break up oil from the BP spill are generally less toxic to test species than oil alone, U.S. Environmental Protection Agency data released on Monday showed.
EPA researchers tested the toxicity of eight kinds of dispersants, including Corexit 9500A, the only such chemical BP has said it used on the spill. The test species were juvenile mysid shrimp and small fish found in the Gulf of Mexico.
Researchers tested the toxicity of Louisiana sweet crude oil alone and on mixtures of this oil with each of the eight dispersants.
Paul Anastas, EPA’s assistant administrator for research and development, said the eight dispersants have similar toxicities to one another and to Louisiana sweet crude oil alone.
“Dispersant-oil mixtures are generally no more toxic to the test species than oil alone,” Anastas told reporters in a telephone briefing. “They would generally be categorized in the moderate range.”
No dispersant has been used on the BP spill in the Gulf of Mexico since July 19, Anastas said. With the well sealed and with permanent killing of the well in prospect, that is likely to continue, but he noted.
He said the EPA and President Barack Obama were committed to “longterm restoration and recovery of the Gulf Coast.”
Anastas echoed EPA’s previously stated stance on the use of dispersants, which have been designated as an “effort of last resort.”
The other dispersants tested by EPA, besides Corexit 9500A, were Dispersit SPC 1000, Nokomis 3-F4, Nokomis 3-AA, ZI-400, SAFRON Gold, Sea Brat #4 and JD 2000.
All eight were found less toxic than the dispersant-oil mixture to both test species, EPA said.
Louisiana sweet crude was more toxic to mysid shrimp than the eight dispersants, when tested alone.
Oil on its own was about as toxic to mysid shrimp as the dispersant-oil mixtures, except for the mixture of oil with Nokomis 3-AA, which was more toxic than oil alone.
BP’s use of dispersant chemicals on the Gulf spill sparked questions from a U.S. congressional panel, which said the company used more dispersant than the EPA had directed.
But the EPA indicated on Sunday that the difference between what the agency directed and what BP and the U.S. Coast Guard used was slight -- the difference between a 75 percent cut in dispersant use and a 72 percent cut.
The environmental agency acknowledged, however, that the use of dispersants is “always a difficult decision.”
Environmental advocates have raised concerns about their use, arguing that the reddish bits of dispersant-treated oil may harm wildlife in the water column between the mile-deep well-head and the Gulf’s surface.
Editing by Todd Eastham