More questions than answers on dispersants a year after spill

One word could describe U.S. EPA's oversight of BP PLC's decision to pour 1.84 million gallons of oil-dispersing chemicals into the Gulf of Mexico during the Deepwater Horizon oil spill: uncertain.

Responding to growing public unease last year over BP's strategy of fighting a massive chemical spill with more chemicals, EPA flexed its regulatory muscle. The result was not confidence-inspiring: a shoving match between the world's largest environmental regulator and one of the world's largest oil companies that showed how little the regulators understood about oil dispersants.

One year later, scientists say little has changed.

Decisionmaking about the use of dispersants to combat the oil pouring out of the Macondo well 5,000 feet below the Gulf surface were driven more by politics, circumstances of supply and availability, and educated guesswork than by informed science, experts say.

Some questions posed during the spill have been answered. For example, the chemical constituents of the dispersant used has been published by EPA and shown in rudimentary tests to be no more toxic or less effective than competing alternatives.

But since the Obama administration has resumed issuing drilling permits in the Gulf of Mexico, the most important questions remain unanswered: How much did dispersants -- as opposed to simple physics -- contribute to keeping oil underwater and out of Louisiana's marshes? How effective was underwater injection of the dispersants onto the wellhead? And what long-term effects will the lingering chemicals and the dispersed oil have on the Gulf of Mexico ecosystem?


"There are so many data gaps and uncertainties with the use of dispersants and their effects," said Carys Mitchelmore, an environmental chemist and toxicologist at the University of Maryland's Center for Environmental Science and co-author of a 2005 National Research Council report on oil dispersants. "Why hasn't there been the funding available to look into some of these things?"

After last year's spill began, regulators seemed confused. Twenty days after the rig explosion, on May 10, EPA told BP to monitor and assess its use of oil dispersants. Ten days later, the agency ordered the oil giant to switch from Corexit-brand dispersant to one of several others believed to be "less toxic and more effective." BP declined and defended its choice. EPA criticized the company's response as "insufficient" and ordered BP to "significantly scale back" dispersant use. BP did not (Greenwire, June 24).

EPA Administrator Lisa Jackson now defends her agency's call to allow BP to fight the spill using dispersants. "The chemicals helped break up the oil," Jackson told The New York Times in a recent interview. "It was the right decision to use them."

If that is the case, then on what basis did EPA decide to order BP to ramp down dispersant use on May 26, two months before the well was capped? EPA officials declined to comment. But other experts have speculated.

"My view is that I think EPA was responding a bit to public concern and pressure," said Ron Tjeerdema, an environmental toxicologist and oil dispersants expert at the University of California, Davis. Tjeerdema was one of 50 scientists, engineers and spill responders that the National Oceanic and Atmospheric Administration assembled during the spill to decide whether to continue using dispersants. The panel concluded that dispersant use should continue.

At that point, questions lingered over whether a better alternative to Corexit existed. A table listing 19 dispersants alongside crude measures of the toxicity and effectiveness of each -- part of the National Contingency Plan (NCP) Product Schedule on file at EPA -- indicated that two Corexit formulas, 9500A and 9527A, might be among the most toxic and least effective formulas in breaking up South Louisiana crude oil (Greenwire, May 13).

The table became the basis of EPA's decision, under pressure from Congress and the public, to order BP to switch to one of the listed alternatives. Mitchelmore said she later found problems and inconsistencies in the testing methods that produced the data listed in the NCP product schedule table's toxicity and effectiveness ratings.

By then, EPA had already ordered BP to switch to something other than Corexit. Upon BP's refusal, EPA launched its own tests to see if a better alternative existed. The results came back two months later on Aug. 2, around the time the well was capped. To the agency's chagrin, BP was shown to be right. EPA's tests showed Corexit 9500A was no more toxic or less effective than any of the competing products, all of which were stockpiled in vastly smaller and ultimately insufficient quantities (E&ENews PM, June 30).

From the early days of the spill, BP's purchase of Corexit represented a third of the world's supply. After the spill, in November, the federal government's Oil Budget Calculator report said of dispersant use: "... were it a spill by itself, it would be one of the larger spills in U.S. waters."

But the scarcity of Corexit alternatives made the decision about whether to switch to some other brand "a moot choice," according to Tjeerdema.

"The oil industry generally only stockpiles one at a time," he said. Tjeerdema recalled chuckling to himself over news reports that BP began dispersing oil using Corexit 9527, an older formula that dates back to the 1980s, before switching to 9527A.

"Right away, I understood they were getting rid of their old stockpile that they hadn't used for 20 years," Tjeerdema said. "They're kind of efficient in wanting to get the most out of their stockpiled dispersants."

Breaking up is hard to do

Dispersants are frequently compared to dish soap -- and in fact, share some of the same ingredients. The chemicals break up oil -- which otherwise tends to cluster and float -- into tiny droplets that can sink and diffuse into the water column, so that bacteria and marine organisms can more easily consume them.

Given the shortage of equipment available during the Deepwater Horizon spill to burn, skim or otherwise dispose of the oil at the surface, the question becomes one of environmental tradeoffs: Should the oil be sunken with dispersants, at possible risk to deepwater marine ecosystems, or be allowed to surface on its own and float onto beaches and into marshes?

Tjeerdema, who served on the NOAA panel that recommended continued dispersant use for the spill last June, stands by the group's consensus that dispersing the oil was "less environmentally harmful" than allowing crude to migrate into the coastal marshes and wetlands along the Louisiana coast, which act as nurseries for economically important fish and shellfish and can be almost impossible to clean.

"If you take dish detergent and squirt it to your aquarium, it will certainly kill your fish," Tjeerdema said. "If you can put 2 million gallons of dispersant into the environment in a way that it will mix and bind with the oil to reduce overall toxicity, maybe that's not such a bad thing."

But the chemicals do not just disappear. In the most comprehensive study on the fate of oil dispersants used in the Gulf spill, Liz Kujawinski, an associate scientist of marine chemistry at the Woods Hole Oceanographic Institution, found that a key ingredient in the dispersants -- dioctyl sodium sulfosuccinate, or DOSS -- remained trapped in the underwater plume of oil that had spread 180 miles from the well by September, even as it became almost undetectably dilute.

"There was sort of a public perception that the dispersant was just going to go away," Kujawinski said. "We concluded that dilution was really the primary process."

But Kujawinski reserves judgment on whether or not dispersing the oil was a good idea. For one, she says, not enough data exists to show what effect, if any, dispersants sprayed deep underwater had on breaking up the oil gushing from the wellhead. She and other researchers note that simple physics may have done more to keep the oil trapped in underwater plumes.

Rather than second-guess the response, Kujuawinski says research should be devoted to answering the most important questions: Did dispersants play a significant role in breaking up the oil at the wellhead and should sinking the oil have been the goal at all?

"We need to take a step back and say it's happened and then say whether or not it did what it's supposed to do," she said, noting that responders had limited equipment for skimming and burning oil that rose to the surface.

"The known negative impact of swamping the marsh with oil -- that's a known problem," Kujawinski said. "The big question is whether or not they caused a different problem."

Answers may not be forthcoming soon. As dolphins and sea turtles continue to wash up mysteriously on the Gulf Coast, only $40 million of the $500 million BP has committed to Gulf research has been disbursed so far because of organizational delays. EPA has proposed additional research into oil dispersants toxicity and effectiveness in 2012, although the agency has come on the chopping block and already faces $1.6 billion in cuts under the budget deal approved last week -- likely the first of many such spending fights.

For now, the puzzle surrounding dispersants remains unsolved, said Lisa Suatoni, senior scientist with the Natural Resources Defense Council.

"In the end, we would hope that the government and BP would have a will to put together that puzzle, and it's not all clear from the research that's coming out that they do have that will," she said. "It's a little discouraging if the interest in oil spill response research lasts only as long as the oil spill response."

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