(CNN) -- The federal government has instructed BP to scale back its use of oil dispersants in the Gulf of Mexico, Environmental Protection Agency Administrator Lisa Jackson said Monday.
Jackson said she believes BP's total use of dispersants can be reduced by as much as 80 percent. While the dispersants are successfully breaking up much of the oil being spilled into the Gulf, she said, "we are making environmental tradeoffs" and are "deeply concerned" about potential side effects.
Jackson and Coast Guard Rear Adm. Mary Landry, the federal on-scene coordinator for the oil spill response effort, told reporters that subsea use of dispersants at the source of the leak will continue. But the federal government strongly prefers to eliminate oil on the surface through a combination of burning and mechanical skimming, they said.
The "use of dispersant in the subsea means that you don't need to spray as much (on the surface)," Jackson later explained. "The idea from the very beginning was that if you could use it in the subsea ... you wouldn't need to spray as much on top."
Jackson's announcement came less than a week after EPA ordered BP to find another chemical dispersant to use on the oil spill after concerns arose about the long-term effects of the substance now being used. Federal officials have been seeking an alternative to the hundreds of thousands of gallons of Corexit 9500 that have been sprayed on the oil slick since April. The product has been rated less effective and more toxic than many others on the list of 18 EPA-approved dispersants, according to testimony at a congressional hearing Wednesday.
Corexit 9500 includes petroleum distillates, propylene glycol and a proprietary organic sulfonic salt, and prolonged contact with it can cause eye or skin irritation, according to the manufacturer's material data safety sheet. The document warns that "repeated or prolonged exposure may irritate the respiratory tract."
"I wasn't satisfied with the answer that we got" from BP regarding possible alternatives, Jackson said. While the data compiled so far does "not show a problem with toxicity" as a result of the use of Corexit, it "seems to me that a month into this and with no end in sight ... we need to ask ourselves whether there's a better product out there. And BP seemed to spend a lot of time saying why everything else didn't work."
The EPA is in the process of setting up a series of toxicity tests, Jackson said, "to look at what's going on out there now and to look at whether there's a better choice."
Asked earlier about the company's continued use of an oil dispersant in the face of an EPA request that it use a less toxic alternative, BP official Tony Hayward said, "Everything that we do with dispersants is with the explicit approval of the EPA."
On Monday, Coast Guard Commandant Adm. Thad Allen -- the Obama administration's point man for the spill -- warned reporters at the White House that the "decision to use dispersants doesn't do away with the problem." It simply means "we are willing to accept the effect of the oil in the ocean rather than on land. It is a trade-off of where the impact of the oil is going to be made."