Updated

COVINGTON, La. (AP) — BP PLC said Saturday it wants to keep using a contentious chemical dispersant to fight the Gulf of Mexico oil spill, despite orders from federal regulators to use something less toxic.

The chemical dispersant at issue, Corexit 9500, is "the best option for subsea application," BP Chief Operating Officer Doug Suttles said in a letter to the Environmental Protection Agency. Tests showed Corexit was among the most effective agents at dispersing the oil, Suttles said.

The EPA raised concerns about the agent Thursday, saying the long-term effects remain unknown. The letter ordered BP to identify an alternative and start using it within three days of its approval by regulators.

"Because of its use in unprecedented volumes and because much is unknown about the underwater use of dispersants, EPA wants to ensure BP is using the least toxic product authorized for use," the agency has said.

EPA officials did not immediately respond Saturday to questions about BP's decision, but will likely decide Sunday on whether the company can continue to use Corexit.

Suttles said BP found five products that met the EPA's criteria, and that Corexit appears to have fewer long-term effects. There was also not enough of the other chemicals immediately available to fight the massive spill, Suttles said.

Louisiana Gov. Bobby Jindal, members of Congress and environmental groups have raised questions about Corexit, which is shot thousands of feet beneath the sea to break apart the oil and keep it from reaching the surface. Safety data documents show Corexit is identified as a "moderate" human health hazard that can cause eye, skin or respiratory irritation with prolonged exposure.

Illinois-based Nalco Co., which makes Corexit, said as long as clean up crews consider the product the best combination of safety, effectiveness and availability, they will continue to supply it.

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Online:

http://www.epa.gov/bpspill/dispersants.html