OR&R Defines the Issues Surrounding Oil Spill Dispersant Use
Aerial view of testing facility with long pool.
The Ohmsett facility is located at Naval Weapons Station Earle, Waterfront. The research and training facility centers around a 2.6 million-gallon saltwater tank. (Bureau of Safety and Environmental Enforcement)
Students in a classroom.
Students listening to the oil dispersant presentation in Seattle. (NOAA)

AUGUST 12, 2014 -- On August 8, 2014, OR&R Emergency Response Division marine biologist Gary Shigenaka and Dr. Adrian C. Bejarano, aquatic toxicologist, made presentations to a group of oil spill response professionals as part of the Science of Oil Spills class, offered by OR&R in Seattle last week.

Shigenaka introduced the subject, giving the students background on the history of dispersant use in response to oil spills, starting with the first use in England at the Torrey Canyon spill.

Because the first generation of oil dispersants were harsh and killed off intertidal species, the goal since has been to reduce their inherent toxicity while maintaining effectiveness at moving oil from the surface of the water into the water column.

He gave an overview of the most prevalent commercial products, including Corexit 9527 and Corexit 9500, manufactured by Nalco, and Finasol OSR52, a French product.

Shigenaka reviewed the U.S. EPA product schedule of dispersants as well as Ohmsett – National Oil Spill Response Research Facility in Leonardo, New Jersey. Ohmsett is run by the U.S. Department of Interior's Bureau of Safety and Environmental Enforcement.

He showed video clips of oil dispersant tests conducted recently at the facility by the American Petroleum Institute.

The corporate proprietary aspects of the exact formulation of dispersants were described by Shigenaka as one of the reasons for the controversy surrounding the use of dispersants on oil spills.

Dispersant Use in Offshore Spill Response

Bejarano's presentation, "Dispersant Use in offshore Oil Spill Response," started with a list of advantages of dispersant use such as reduced oil exposure to workers; reduced impacts on shoreline habitats; minimal impacts on wildlife with long life spans; and keeping the oil away from the nearshore area thus avoiding the need for invasive cleanup. She followed with some downside aspects such as increased localized concentration of hydrocarbons; higher toxicity levels in the top 10 meters of the water column; increased risk to less mobile species; and greater exposure to dispersed oil to species nearer to the surface.

Bejarano is working on a comprehensive publicly-available database that will include source evaluation and EPA data as well as a compilation of data from 160 sources scored on applicability to oil spill response (high, moderate, low and different exposures).

Her presentation concluded with a summary of trade-offs associated with dispersant use:

  • Shifting risk to water column organisms from shoreline, which recover more quickly (weeks or months).
  • Toxicity data are not perfect.
  • Realistic dose and duration are different from lab to field environment.
  • Interpretation of findings must be in the context of particular oil spill considerations.

Bejarano emphasized the need for balanced consideration in reaching consensus for the best response to a particular spill.

Following the formal presentations, there was a panel discussion with experts from NOAA, the U.S. Environmental Protection Agency, and State of Washington, and the audience had an opportunity to ask questions. Recent research from the NOAA National Marine Fisheries Service Montlake Laboratory was presented, focusing on effects of oil and dispersants on larval fish. The adequacy of existing science underlying trade-offs and net environmental benefit was also discussed.