WASHINGTON — Concerns are mounting over the chemical dispersants that BP is using to fight the oil spill in the Gulf of Mexico now that over 1 million gallons of the chemical have been pumped into Gulf waters.
Nonetheless, a federal study says using the dispersants is less harmful to the environment than if the oil reaches shorelines.
"Up to this point, (the) use of dispersants and the effects of dispersing oil into the water column has generally been less environmentally harmful than allowing the oil to migrate on the surface into the sensitive wetlands and near shore coastal habitats," said the report done for the National Oceanic and Atmospheric Administration.
But retired Coast Guard Adm. Thad Allen said Monday that officials are now worried about the toxicity of the chemicals — Corexit 9500 and Corexit EC9527A — and will begin cutting back on their use.
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"I believe they're worthwhile. But I think there's enough concern as we approach the million-gallon mark ... regarding the unknown implications of that amount of dispersants," Allen said.
According to the Environmental Protection Agency, about 1.08 million gallons of dispersant have been deployed in the Gulf, with 779,000 gallons used on the surface and 303,000 gallons used underwater.
Jerald Ault, a professor at the University of Miami, said Corexit could have "significant" effects on the food chain and on environmental and human heath.
"It's uncharted waters and the magnitudes are so large," Ault said of the potential consequences and of the reports that dolphins and other animals are dying from the chemicals. "Eventually the correlation starts to say, (the animals) weren't dying before and they are dying now. Geez, I wonder what the correlation is."
In a letter to BP CEO Tony Hayward, officials from Louisiana asked about the unknown effects of dispersants.
"As heads of Louisiana's agencies that oversee public health, environmental quality and wildlife and fisheries ... we have serious concerns about the lack of information related to the use of dispersants in fighting the oil spill at and below the surface of the Gulf of Mexico, and what, if any, impact the dispersants could have on our people, water and air quality," the letter read.
BP replied and sent documents from Nalco — the manufacturer of Corexit — that classified the health and environmental risks as "low," despite the fact that one of the ingredients causes damage to red blood cells and kidneys in laboratory animals.
"However, human studies suggest that humans are relatively resistant to any such effects or once the dispersant is applied, it is diluted and broken down in the environment," BP said.
Carys Mitchelmore, a professor with the University of Maryland, noted there has not been adequate research to say if Corexit, or any dispersant, is more harmful than oil. Without the chemicals, Mitchelmore said, the shorelines would be flooded with oil.
"What you're doing is ... making an environmental tradeoff. You're not getting oil coming to those shorelines. What you're doing though, is dispersing that oil down ... down into the ocean where you're going to be killing and impacting the environment there," she said. And the long-term effects are unknown, she added.
The EPA originally approved the use of dispersants on May 10, and BP has defended the use of the chemicals even after the agency began questioning the toxicity levels. Ault said dispersants allow the oil to break down under the water.
"It's trying to reduce the surface impact," he said. "The reason they are using it is to reduce the obvious visual effect."