From the Executive Director: Dispersant use in spill response a concern for many

By Mark Swanson
Executive Director
Prince William Sound Regional Citizens’ Advisory Council.

The council has long been skeptical about the use of dispersants in responding to oil spills in our local waters. Until they can be shown to be effective and environmentally beneficial, the council does not recommend their use and advocates for mechanical clean-up options with booms and skimmers that physically remove the spilled oil from the environment.

How do dispersants work?

The theory behind dispersants is that in some situations it may be environmentally preferential to chemically disperse spilled oil into the water column rather than allow spilled oil to hit a beach or shoreline. In theory, this would dilute the oil throughout the water column, reducing the acute concentrations and toxic effects of oil on the water’s surface. The increased surface area and smaller oil droplet size then helps expedite biodegradation from oil degrading bacteria.

Why is the council concerned about dispersants?

Council research has shown that dispersant effectiveness is significantly decreased in the cold and low salinity waters of Prince William Sound. Our research indicates that the underwater mixing depth available for dispersion in deep coastal Alaskan waters is reduced, in warmer months, to a shallow freshwater lens of glacial runoff and snow melt water sitting atop the denser saltwater. Council-funded laboratory studies have also shown that chemically dispersed oil is more toxic than naturally dispersed oil. These studies have demonstrated that key local species like herring, salmon and cod are adversely affected when exposed to far lower hydrocarbon concentrations than previously suspected, in the parts per billion realm rather than parts per million. Actual experience with dispersed oil in Alaskan waters is relatively limited and includes only small dispersant applications trialed during the Exxon Valdez oil spill in 1989.

The Environmental Protection Agency’s listing of dispersants as an approved response product in the National Contingency Plan is currently based on manufacturer-supplied effectiveness and toxicity data. The agency is in the process of updating this part of the plan, but the process has been slow. As of July 2013, the updated rule is with Office of Management and Budget and will next go out for public comment. There are many shortcomings with the current “approved product schedule” that need to be addressed, including:

  • The toxicity data provided by the manufacturers is based on short term exposure mortality results for two species that don’t even exist in Alaskan waters: mysid shrimp and silverside minnows.
  • There is no consideration of human exposures.
  • There is no consideration of dispersed oil impacts to other locally important or endangered species, unless local response teams decide to require toxicity testing.

The council is conducting limited research on one whale species but the impacts of chemically dispersed oil on other endangered species present in Alaska is largely unknown.

In summary, due to our cold and highly stratified water column and the lack of research on local species in regards to dispersant impacts, dispersants simply do not seem like the best option for our local waters.

The BP spill focused public attention on dispersants

Due to the unprecedented extensive application of dispersants both at the surface and at the ocean floor well head during the BP Deepwater Horizon oil spill in 2010, significant additional public attention and research has been focused on dispersants. Whether it was dispersants or other factors, it appears that much of the oil stayed in the water column instead of collecting on the surface and impacting beaches and life on the surface. The short and long term environmental impacts of dispersant use in the Gulf of Mexico are still being studied but initial reports generally appear less than positive.

Diverse views on dispersants

Following the Deepwater Horizon spill, the scientific community and a wide swath of environmental organizations seem to have increased their anecdotal and research-backed reasons for questioning the use of dispersants. At the same time, some federal oil spill response managers appear to see dispersants as a far more effective oil spill response tool than mechanical recovery. These agencies are pushing to ensure that dispersants are pre-approved for use in every state and region. The ongoing update of the Alaska Regional Response Team’s Dispersant Usage Guidelines is part of that larger national process, and the council has provided comments. These comments support the idea of basing dispersant use decisions on the clarification of critically important local effectiveness and environmental impact-benefit questions. This can in part be achieved by directing spill response coordinators to appropriate incident specific consultations with resource trustee agencies.

Other groups are becoming galvanized around the issue of dispersants. Dozens of coastal Alaska Native tribal councils have signed resolutions opposing the use of dispersants in their subsistence waters. In May, three environmental organizations won a lawsuit requiring the federal agencies in charge of oil spill response in the San Francisco area to establish the impact on their local endangered species prior to pre-approval of dispersants. Three other organizations coordinated a national day of action to ban dispersants on June 18th.

The bottom line is that dispersant use is a concern to many. With national public response policy running in apparent opposition to gathering public environmental and human health concerns, the need for stakeholder engagement on this issue is great.

For a summary and links to key council research on this issue please visit our website:

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