"The EPA Directed BP to stop using Corexit 9500 and come up with a substitute in 3 days. BP objects"

So, why does EPA not direct BP to use a specific product and procedure, if it knows of one? Is it reasonable to speculate that EPA does not wish to take on the liability, if there is a mistake? I suspect BP (and EPA) both know the scientific data on all the dispersants and to limit effects and liability chooses the one it knows to be the most efficient. However, in these conditions, I doubt that there is much non-labratory data to give any certainity on the impacts (local, fnear and far field, and short and longer term) on any dispersant in this unique situation. It may come down to a determination on what it is that you want to protect and what has the greater liability? A microscopic ecosystem, and long term effects would likely be less visible and costly (and difficult to determine and see) than coastal assets. Who even remembers (or knows of) the offshore ecosystem costs to other big spills in the Gulf?