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Concept.png Corexit 
(Chemical,  "Safe and Effective")Rdf-entity.pngRdf-icon.png
Chemical that is used on oil spills to dissolve them.

Corexit is a oil dispersants used during oil spill response operations.

It is typically applied by aerial spraying or spraying from ships directly onto an oil slick. On contact with the dispersant, oil that would otherwise float on the surface of the water is emulsified into tiny droplets and sinks or (in the unusual case of sub-surface application) remains suspended in the water. In theory this allows the oil to be more rapidly degraded by bacteria (bioremediation) and prevents it from accumulating on beaches and in marshes.[1]

Deepwater Horizon

Corexit was used in unprecedented quantities during the 2010 Deepwater Horizon oil spill in the Gulf of Mexico and became the largest use of such chemicals in the United States. In addition to spraying the dispersant onto the surface slick, it was used in an untested, off-label manner when BP injected it at the broken well-head, roughly 1,500 m (5,000 ft) below the surface. Researchers continue to examine the effects and effectiveness of Corexit. Studies have so far indicated that the dispersant is toxic to marine life. Corexit has been shown to exert a synergistic effect when mixed with oil, increasing its toxicity. During the 2010 spill, the ecological effect of mixing the dispersants with oil was unknown, as was the toxicity of the breakdown products of the dispersant.


Corexit is banned in the United Kingdom due to concerns about possible adverse health effects on people using it.

Prior to the 2010 Gulf spill, the majority of studies performed on Corexit tested for effectiveness in dispersing oil, rather than for toxicity. The manufacturer's safety data sheet stated:

"No toxicity studies have been conducted on this product," and later concludes "The potential human hazard is: Low."

According to the manufacturer's website, workers applying Corexit should wear breathing protection and work in a ventilated area.

Rhode Island Sen. Sheldon Whitehouse said the EPA was not prepared to responsibly authorize BP's use of Corexit, but did so anyway. He noted that manufacturers could nominate themselves to EPA's list of approved dispersants. Although they had to provide data on both efficacy and toxicity, there was no official toxicity limit to bar approval.

Chemist Wilma Subra expressed her concern about the danger of the Corexit-crude mixture, telling GAP investigators, “The short-term health symptoms include acute respiratory problems, skin rashes, cardiovascular impacts, gastrointestinal impacts, and short-term loss of memory....long-term impacts include cancer, decreased lung function, liver damage, and kidney damage.”

Nalco spokesman Charlie Pajor said that oil mixed with Corexit is "more toxic to marine life, but less toxic to life along the shore and animals at the surface" because the dispersant allows the oil to stay submerged below the surface of the water. Corexit causes oil to form into small droplets in the water; fish may be harmed when they eat these droplets. According to its Material safety data sheet, Corexit may also bioaccumulate, remaining in the flesh and building up over time. Thus predators who eat smaller fish with the toxin in their systems may end up with much higher levels in their flesh. The influence of Corexit on microbiological communities is a topic of ongoing research.

A study of 247 BP oil spill clean-up workers released in September 2013 by the American Journal of Medicine showed the workers were at an increased risk of developing cancer, leukemia and other illnesses. The study concluded that "clean-up workers exposed to the oil spill and dispersant experienced significantly altered blood profiles, liver enzymes, and somatic symptoms."

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