Oil-spill dispersants are toxic to corals

Oil dispersants, the tool of choice for treating oil spills in tropical oceans, turn out to be significantly more toxic to marine life than the crude oil itself, according to a study on corals (Environ. Sci. Technol. 2007, 41, 5571). An Israeli research team led by Shai Shafir of the National Institute of Oceanography and Hebrew University of Jerusalem evaluated the short- and long-term impact on more than 10,000 specimens of two coral species exposed in the lab to crude oil or crude oil treated with different commercial oil dispersants. The dispersants contain surfactants and/or solvents that break down the oil into small droplets, which help prevent oil spills from reaching shore. The researchers observed that exposure to the manufacturer-recommended dispersant concentrations killed all of the coral samples while many of the samples exposed to the water-soluble fraction of crude oil survived. "Decision-making authorities should carefully consider these results when evaluating possible use of oil dispersants as a mitigation tool against oil pollution near coral reef areas," they note.