A month ago the Environmental Protection Agency ordered BP to stop spraying so much dispersant on oil gushing from the Deepwater Horizon well and to find a less toxic alternative to the chemical it was using.
BP is still spraying the same stuff — under the brand name Corexit — that led to EPA concerns in May. Although it has decreased the total amount used, BP has exceeded the recommended daily level of 15,000 gallons sprayed beneath the surface of the Gulf of Mexico. And so far, neither BP nor the EPA has found an effective but less toxic alternative to Corexit.
Meanwhile, federal scientists confirmed this week what University of South Florida researchers and others had found: plumes of tiny oil droplets that stretch for miles underwater, which "is consistent with chemically dispersed oil." Some of it, they found, had oozed into shallower waters close to shore.
"That's particularly troublesome," said Ernst Peebles, a biological oceanographer at USF. Contaminants in the shallower water — about 30 feet deep — can be blown around more easily by wind, spreading it along the gulf's biologically rich continental shelf, he explained.
The bottom line, Peebles said, is that thanks to the dispersants "the oil is more broadly distributed than it would have been, and the oil droplets do have toxic properties. It appears to be creating layers of microscopic oil droplets that are spread throughout the gulf."
But EPA Administrator Lisa Jackson said this week that her agency will continue allowing dispersant use because "dispersants are one tool in a situation that could not be more urgent" — even though, she acknowledged, "We know that they come with environmental trade-offs."
About 1.47 million gallons of dispersant have been applied to the gushing oil so far, an unprecedented amount. Of that, 972,000 gallons were sprayed on the surface, while 493,000 gallons were sprayed deep underwater — the first time anyone has sprayed dispersant below the surface.
The company has sprayed 272,000 gallons of it on the surface since the EPA edict was issued a month ago, and 342,000 gallons below the surface.
"We're using the product that's been approved by the government," BP spokesman Bryan Ferguson said. As for the subsea plumes of dissolved oil droplets, Ferguson said, "We're still evaluating and investigating that and we have no comment."
In May the EPA ordered BP to cut total dispersant use by 75 percent from the peak of 70,000 gallons a day. So far, Jackson said, the company has cut its total use by 68 percent.
In letters sent Thursday to the EPA and Coast Guard, House Energy and Environment Subcommittee chairman Ed Markey, D-Mass., complained that the dispersants were "contributing to a toxic stew of chemicals, oil and gas with impacts that are not well understood."
Scientists do know that some marine life is more sensitive to dispersants than others. Crustaceans, algae and fish larvae find low concentrations of Corexit toxic, according to Carys Mitchelmore, a University of Maryland expert on oil dispersants.
Dispersants mixed with oil can be as toxic, if not more toxic, than the oil itself. In fact, Mitchelmore testified to a congressional panel last week, dispersants may actually make it easier for fish, oysters, mussels and other marine life to absorb the oil.
Ideally the dispersed droplets would be consumed by oil-eating bacteria that live throughout the gulf. But when there's a large concentration of oil in the water, the bacteria can flock to it in such numbers that they use up all the dissolved oxygen in the water nearby, suffocating other marine life.
Though the ship sent by the National Oceanic and Atmospheric Administration found no signs of a lowered oxygen level around the plume, scientists who studied test results warned that the dissolved oxygen "could decrease approximately 10 percent in the deep water if a significant fraction of oil remains subsurface and the rate of dispersion of the oil is low."
Some Louisiana cleanup workers have complained of being sprayed with dispersant from planes hired by BP, and reported skin irritation, headaches and nausea. But federal officials said they had been monitoring the dispersant use and so far had found no human exposure problems.
Information from the New York Times was used in this report. Craig Pittman can be reached at firstname.lastname@example.org or (727) 893-8530.