BP continued spraying large amounts of a controversial dispersant onto the surface of the Gulf of Mexico even after an EPA order to stop doing so, the Washington Post reports.

According to the Post, BP used a loophole in the EPA's order that allowed the Coast Guard to rubber-stamp "exemptions" to the order.

In late May, under pressure from environmental groups, the EPA ordered BP to stop using certain product lines of the dispersant Corexit on the water surface. But it allowed the Coast Guard -- which has the final say on oil cleanup operations -- to issue exemptions in "rare" circumstances. The Post found that those circumstances weren't rare at all:

Despite the order -- and concerns about the environmental effects of the dispersants-- the Coast Guard granted requests to use them 74 times over 54 days, and to use them on the surface and deep underwater at the well site. The Coast Guard approved every request submitted by BP or local Coast Guard commanders in Houma, La., although in some cases it reduced the amount of the chemicals they could use, according to an analysis of the documents prepared by the office of Rep. Edward J. Markey (D-Mass.).

The documents indicate that "these exemptions are in no way a 'rare' occurrence, and have allowed surface application of the dispersant to occur virtually every day since the directive was issued," Markey wrote in a letter dated Aug. 1 to retired Coast Guard Adm. Thad W. Allen, the government's point man on the spill. Markey chairs the House Select Committee on Energy Independence and Global Warming.

In the words of Rep. Markey, the order became "a meaningless paperwork exercise."

Many marine biologists have raised concerns about the potential environmental and health effects of Corexit, which is used to break down oil.

A marine toxicologist working in the Gulf found that shrimpers who came into contact with a mixture of oil and Corexit suffered severe symptoms such as muscle spasms, heart palpitations, headaches that last for weeks and bleeding from the rectum.

A marine biologist said earlier this month that the Corexit used in the cleanup operation has made its way onto land and is "mixing with our everyday lives."

The Post reports that the use of Corexit to break down the oil may have resulted in an environmental "trade-off."

Now, scientists say, it's difficult to tell what the added use of dispersants permitted by the Coast Guard meant for the gulf. The chemicals may have helped break up some oil before it reached sensitive marshes along the Louisiana coast. But it also may have poisoned ecosystems offshore, helped deplete underwater oxygen and sent oil swirling through the open-water habitats of fish and coral.

Coast Guard Adm. Thad Allen, the head of the cleanup operation, defended the use of Corexit to the Post.

"There's a dynamic tension that goes on when you're managing an incident that has no precedent," Allen said. "You establish general rules and guidelines, but knowing that the people on scene have the information" means trusting them to make decisions, he said.

In the end, Allen said: "You can quibble on the semantics related to 'rare.' I like to focus on the effects we achieved" by dispersing the oil. Officials have said that, in the days since the gusher was stopped, thick sheets of oil have nearly disappeared from the gulf's surface.