In response to the EPA's call for BP to "significantly scale back" its use of dispersants in the Gulf disaster, BP's average daily use of dispersant has decreased only 9 percent.

That's according to a calculation done by Richard Denison, a senior scientist at the Environmental Defense Fund, using the dispersant statistics provided daily by Deepwater Horizon Unified Command, the working group of federal agencies and companies involved in the spill, including BP.

Last month, the EPA initially demanded that BP find a less toxic alternative to Corexit, after journalists and scientists raised concerns about its toxicity and its unprecedented subsurface application. When BP resisted the order, telling the EPA it couldn't find a suitable alternative, the EPA said it would perform studies on Corexit and asked BP to "significantly scale back" its use of the chemicals.

Here's exactly what EPA Administrator Lisa Jackson told reporters on a conference call on May 24 (PDF), emphasis added:

By ramping down on the amount of dispersant used, particularly on the surface where we expect less undispersed oil, we believe we can reduce the amount of dispersant applied by as much as half, and I think probably 75 percent, maybe more.

What journalists weren't told in that conversation was how the reduction would be calculated. The EPA, two days later, issued an addendum to the directive [PDF] telling BP to "establish an overall goal of reducing dispersant application by 75% from the maximum daily amount." (emphasis added)

Given that the most dispersant ever applied by BP in one day was about 70,000 gallons, on May 23, the EPA says BP has reduced its use of dispersant by 68 percent. But average daily use has only gone from 24,700 gallons before the directive to 22,600 after the directive, just a slight reduction. 

We've called the EPA to give it a chance to comment, but it hasn't given me an on-the-record response. As Mother Jones points out, it has been a month and the EPA's own dispersant testing has still not been completed.

While Corexit dispersant has been linked to human health problems, its long-term effects on the environment remain uncertain. For the time being, scientists studying the use of dispersant in the Gulf have concluded (PDF) that "continued dispersant use trades shoreline impacts for water column impacts," but that using dispersants is "less environmentally harmful" than the alternative.

Update: The EPA just responded to us with a statement. Read it in full.