So that's what happened to all the oil? Despite an order issued by the Obama administration to curb the use of dispersants, which work like soap on kitchen grease to break up oil in the water and make it easier for microbes to digest, the Coast Guard approved every request BP made to use them. According to a report issued by the office of Representative Edward Markey of Massachusetts, the Coast Guard granted BP's requests 74 times over 59 days. Markey said that the order "has become more of a meaningless paperwork exercise." Though an investigation into the environmental effects of dispersants was begun after they were used to clean up the Exxon Valdez spill in 1989, it faltered as the spill was forgotten, and the environmental impact of the chemicals is still unknown. Carys Mitchelmore, a professor at the University of Maryland said that by using dispersants "you're just going to be killing more things in the water column." Retired Admiral Thad Allen, who's heading the government response to the spill, defended the approval of dispersants, saying their total use declined after the administration's May 26 order, and that the decision to use them was a "tactical" one, made by people on the scene.