|Offshore Oil Spills: Additional Information is Needed to Better Understand the Environmental Tradeoffs of Using Chemical Dispersants|
When an oil spill occurs, responders have several options to manage the environmental effects, including using chemical dispersants (see figure). Chemical dispersants used on a surface oil slick can be effective at breaking up floating oil, which can help prevent the oil from reaching shore and harming sensitive ecosystems, according to studies GAO reviewed and stakeholders GAO interviewed. However, the effectiveness of applying dispersants below the ocean surface—such as in response to an uncontrolled release of oil from a subsurface wellhead—is not well understood for various reasons. For example, measurements for assessing effectiveness of dispersants applied at the subsurface wellhead during the Deepwater Horizon oil spill had limitations and were inconclusive. In addition, there are limited experimental data on the effectiveness of subsurface dispersants that reflect conditions found in the deep ocean.