According to the Washington Post, the EPA "informed BP officials...that the company has 24 hours to choose a less-toxic form of chemical dispersants to break up its oil spill in the Gulf of Mexico...and must apply the new form of dispersants within 72 hours of submitting the list of alternatives." Of course, there's still a lot of information we don't know about these chemicals...

The directive is posted on the dispersant page of EPA’s website as Addendum 2 to EPA's Dispersant Monitoring and Assessment Directive for Subsurface Dispersant.