Study: Dispersant used to clean BP spill makes oil 52 times more toxic

Michael Bastasch | Contributor

A new study found that oil dispersant used to clean up the massive Deepwater Horizon spill made the oil more toxic and likely wreaked havoc on the marine food chain, reports Live Science.

The study, published by researchers in the journal Environmental Pollution, found that the oil dispersant called Corexit 9527A and 9500A, which is used to help oil degrade more quickly, becomes up to 52 times more toxic when combined with oil.

“There is a synergistic interaction between crude oil and the dispersant that makes it more toxic,” said Terry Snell, a co-author of the study and biologist at Georgia Tech. “That probably put a big dent in the planktonic food web for some extended period of time, but nobody really made the measurements to figure out the impact.”

Researchers tested ratios of the oil from the well that leaked in the Deepwater Horizon and the dispersant. The study found that the mixture was similarly toxic for the various ratios tested.

The researchers also exposed several varieties of rotifers — planktonic organisms — to concentrations likely seen over a large area of the Gulf.

“The levels in the Gulf were toxic, and seriously toxic,” Snell said. “That probably put a big dent in the planktonic food web for some extended period of time, but nobody really made the measurements to figure out the impact.”

Ian MacDonald, a researcher at Florida State University who was not involved in the study, told Live Science that the dispersant makes the oil more toxic by decreasing the size of the droplets which makes it more “bio-available” to small organisms.

The study’s results contradict 2010 findings by the Environmental Protection Agency that found that the oil and Corexit mixture is no more toxic than oil alone to species of shrimp and fish.

“To date, EPA has done nothing but congratulate itself on how Corexit was used and avow they would do it the same way again,” MacDonald said.

Live Science notes that other studies have found the mixture is actually more toxic than oil to the embryos of several species of fish.

“This is a cautionary tale that we need to do the science before the emergency happens so we can make decisions that are fully informed,” Snell said. “In this case, the Corexit is simply there to make the oil disperse and go out of sight. But out of sight doesn’t mean it’s safe in regard to the food web.”

While tempting to want to do something to mitigate an oil spill, it would be better to not use the dispersant and let the oil dissipate on its own to minimize ecological damage, Snell cautioned.

“It’s hard to sit by and not do something,” Snell added.”But in this case, doing something actually made it more toxic.”

More than 2 million gallons of Corexit was dumped into the Gulf of Mexico in 2010 to stop oil from hitting the shore and to degrade it more quickly.

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