Offshore Oil Spills: Additional Information is Needed to Better Understand the Environmental Tradeoffs of Using Chemical Dispersants, Report to Congressional Requesters [open pdf - 3MB]
From the Highlights: "In April 2010, an explosion onboard the 'Deepwater Horizon' drilling rig in the Gulf of Mexico resulted in 11 deaths and the release of approximately 206 million gallons of oil. During the 'Deepwater Horizon' oil spill, responders applied dispersants to the oil slick at the ocean surface as well as at the wellhead more than 1,500 meters below the surface. The subsurface use of dispersants was unprecedented and controversial. GAO [Government Accountability Office] was asked to review what is known about the use of chemical dispersants. This report examines, among other things, what is known about the effectiveness of dispersants, what is known about the effects of chemically dispersed oil on the environment, and the extent to which federal agencies have taken action to help ensure decision makers have quality information to support decisions on dispersant use. GAO reviewed scientific studies, laws, regulations, and policies. GAO also interviewed agency officials and stakeholders from academia and industry."
Government Accountability Office: http://www.gao.gov