Dispersant made 2010 Gulf of Mexico spill up to 52 times more toxic

USPA News - A dispersant used as part of efforts to clean up oil from the 2010 Deepwater Horizon disaster is believed to have made the spill up to 52 times more toxic, according to new research. The ecological disaster was the worst U.S. oil spill in history.

The dispersant, Corexit, is required by the U.S. Environmental Protection Agency (EPA) for clean up following oil spills. But researchers from the Georgia Institute of Technology and the Autonomous University of Aguascalientes (UAA) in Mexico found the dispersant makes the oil up to 52 times more toxic when they are mixed. "Dispersants are pre-approved to help clean up oil spills and are widely used during disasters," said UAA`s Roberto-Rico Martinez, who led the study. "But we have a poor understanding of their toxicity. Our study indicates the increase in toxicity may have been greatly underestimated following the Macondo well explosion." In toxicity tests in the lab, the mixture`s effects increased mortality of rotifers, a microscopic grazing animal at the base of the food web in the Gulf of Mexico. In addition to causing mortality in adult rotifers, as little as 2.6 percent of the oil-dispersant mixture was needed to inhibit rotifer egg hatching by 50 percent. The researchers, whose findings were published online on Friday and will appear in the print edition of Environmental Pollution in February, said inhibition of rotifer egg hatching from the sediments is important because these eggs hatch into rotifers each spring, reproduce in the water column, and provide food for baby fish, shrimp and crabs in estuaries. "What remains to be determined is whether the benefits of dispersing the oil by using Corexit are outweighed by the substantial increase in toxicity of the mixture," said Georgia Tech School of Biology Professor Terry Snell. "Perhaps we should allow the oil to naturally disperse. It might take longer, but it would have less toxic impact on marine ecosystems." On April 20, 2010, BP`s Deepwater Horizon oil platform exploded, killing eleven men and ultimately releasing an estimated 4.9 million barrels of oil into the Gulf of Mexico. BP was finally able to seal the well with cement 18,000 feet (5,486 meters) below the sea in September 2010.