Over the past couple of days, I have gotten several questions about dispersants that are being used to combat the ever-growing oil slick in the Gulf: What do dispersants do? Are they effective? Are they toxic? What happens to the oil? I will be the first to admit that I cannot come close to answering all of these questions, but based on the research I have done here are my impressions: Photo from Associated PressFirst, dispersants do not magically make oil from a spill disappear. In theory, they are used to increase the amount of oil that mixes with the water and sinks, thus reducing the surface slick which can contaminate coastal wetlands and beaches along with marine mammals and other wildlife. They can often be effective in achieving the very limited goal of reducing the volume of the surface slick.However, there is a major trade-off involved. The oil that is “dispersed” from the surface ultimate ends up in the water column, and at the bottom of the oceans – endangering the marine life that resides in these areas. The most commonly used dispersant, Corexit 9500, can be toxic to crustaceans at relatively low levels and there are significant concerns about what effect the combined oil and dispersants will have on bottom-dwelling critters, as well as larval fish.There is a remarkable lack of study on how dispersants affect the water column, and wildlife but we do know that the oil that is “dispersed” is likely to remain hidden below the Gulf for some time to come. It’s is difficult to say whether or not dispersants should be used and under what circumstances, but it is obvious that we do not know enough about these dispersants. This is why I suggest that independent scientists, university scientists, and agencies, such as NOAA and EPA, begin studying these dispersed oils in the Gulf immediately to ensure that we are not making an ill-fated tradeoff, and so if a big spill happens again, we will be better prepared.To read my more in-depth analysis, go here .There has been a bit of coverage regarding dispersants over the past couple of days, I would suggest taking a look at what the Lower Mississippi Riverkeeper, and NRDC have been posting on the issue. Also check out recent articles in the New York Times and Grist.Matt is Water Resources Program Director for GRN
