The Environmental Protection Agency has authorized BP to use chemical dispersants to break up the oil sludge in the Gulf. But now, the agency has informed the company that it has 24 hours to identify a less toxic chemical for the job.

Update: The EPA released a statement Thursday afternoon calling on BP to use a more effective and less toxic form of dispersant, both on the surface and underwater, within 72 hours:

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. We reserve the right to discontinue the use of this dispersant method if any negative impacts on the environment outweigh the benefits.

The Washington Post had the scoop:

The move is significant, because it suggests federal officials are now concerned that the unprecedented use of chemical dispersants could pose a significant threat to the Gulf of Mexico’s marine life. BP has been using two forms of dispersants, Corexit 9500A and Corexit 9527A, and so far has applied 600,000 gallons on the surface and 55,000 underwater.

“Dispersants have never been used in this volume before,” said an administration official spoke on condition of anonymity because the decision hasn’t been formally announced. “This is a large amount of dispersants being used, larger amounts than have ever been used, on a pipe that continues to leak oil and that BP is still trying to cap.”

Earlier this week, ProPublica reported that the forms of dispersant currently used by BP are banned in the U.K., and added:

BP is using two products from a line of dispersants called Corexit, which EPA data appear to show is more toxic and less effective on South Louisiana crude than other available dispersants, according to Greenwire.

The EPA’s addendum to its original directive to BP can be read here:

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