(See Related, “Oil Spill Hits Gulf Coast Habitats”)

The joint federal-industry response team responsible for the cleanup effort reports that nearly 140,000 gallons (529,928 liters) of dispersants have been used so far, with an additional 51,000 gallons (193,056 liters) available. Responders also have been trying controlled burns and have deployed long lines of inflatable booms, but they have said the chemicals have proven the most effective method of attacking the spill so far.

"Even on the Exxon Valdez spill, dispersants weren't used all that readily," Gaudiosi said. The notorious 1989 tanker disaster, up until now the worst oil spill in U.S. history, dumped 11 million gallons (41.6 million liters) on the remote Prince William Sound in Alaska.

But the spill