Corexit 9527A

Corexit (often styled COREXIT) is a product line of oil dispersants used during oil spill response operations. It is produced by Nalco Company, associated with BP and Exxon and an indirect subsidiary of Ecolab. Corexit was originally developed by the Standard Oil Company of New Jersey. Corexit 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.

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 5,000 feet 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.

Corexit was originally developed by the Standard Oil Company of New Jersey (SONJ) also known as Esso (phonetically derived from the acronym SO). The company later merged with Humble Oil to form Exxon, which is now part of ExxonMobil.

In 2011, Corexit became the property of Ecolab, following a merger between Ecolab and Nalco Holding Company. As of 2015, Corexit is owned by Ecolab and is manufactured by Nalco Company, an indirect subsidiary of Ecolab.

Dispersants are mixtures of surfactants and solvents that are commonly used to break up floating oil slicks into small droplets, which are submerged underwater. This reduces shoreline accumulation but increases the amount of oil underwater. This also increases the surface area of the oil and, in theory, accelerates the destruction of oil by naturally occurring bacteria. Dispersants are themselves a form of pollution that can be toxic to marine life, and the increased activity of bacteria from their presence can deplete oxygen in nearby waters, causing further harm to marine life. There are important trade-offs that must be considered in their use, such as the relative level of toxicity of the dispersant versus the relative toxicity of the spilled oil, to ensure that dispersant use mitigates an oil spill rather than to make the problem worse.

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