BP is using dispersants to mitigate the effects of the oil spill in the Gulf of Mexico. A dispersant breaks up large patches of oil on the surface and forces them to sink into the ocean. Some dispersants are toxic, some are less toxic. The dispersant BP is using is called Corexit. According to the MSDS, it is a hydrocarbon with several other additives. Nalco, the manufacturer, does not give the exact formulation of Corexit, likely because it is a trade secret. This makes it very difficult to determine the toxicity of this dispersant.
Searching for more information on the formulation gives some information on the typical components of a dispersant. The National Academy of Sciences mentions some of the chemicals which make up a surfactant. There are ionic and nonionic chemicals present in the surfactant. Nonionic surfactants that are in Corexit surfactants include sorbitan oleates and their derivatives. Sorbitan oleate is an emulsifier and an oil soluble surfactant. Derivatives include several chemicals known as tweens, such as Tween 80. Tween 80 itself is safe enough to be used as a food ingredient, but manufacturing it requires the use of the precursor ethylene oxide, which is a carcinogen and might be present as an impurity. Tween 80 is also known as polysorbate 80. This substance includes very long chain hydrocarbons, so it is related to fats and oils and it is soluble in petroleum. According to the National Academy of Sciences, the chemical sodium dioctyl sulfosuccinate is the main ionic surfactant. It is also considered safe for use in food as a cocoa additive, according to Ohio State.
Scientists at the University of California, Davis specifically tested one type of Corexit, Corexit 9500, to determine its toxicity for sea life. UC Davis is a large university in Davis, a town outside California’s capital, Sacramento. This school has a great reputation for research, and it is one of the best ranked universities in California. Davis focuses heavily on agricultural research because of its inland location near a lot of farmland around the state capital. The main conclusion from this study is that the different formulations of Corexit had similar toxicities. Corexit 9500 is designed to be less toxic than the previous formula, Corexit 9527. According to the National Academies the Corexit solvent was changed from glycol ether, which was irritating people, to a variety of long chain hydrocarbons, basically chains longer than octane like nonane and decane, up to hexadecane where anything with a longer chain isn’t liquid at room temperature anymore and behaves more like a wax.
Corexit appears to have irritant effects on humans from what I’ve seen so far, although many individual components are safe. It does seem like it can interfere with the respiration of sea life according to the UC Davis study. The oil spill itself is going to kill a lot more sea animals than the dispersant will. There is an alternative, Dispersit, which is designed to create less problems than Corexit. According to Elon University, a study on Dispersit shows that it is harmful to brine shrimp.