Study in Progress

Evaluation of the Use of Chemical Dispersants in Oil Spill Response

The crew of a Basler BT-67 fixed wing aircraft release oil dispersant over an oil discharge from the mobile offshore drilling unit, Deepwater Horizon, off the shore of Louisiana, May 5, 2010.

Statement of Task

This study will assess the effects and efficacy of dispersants as an oil spill response tool through review and evaluation of domestic and international research reports and results. The study will evaluate trade-offs associated with dispersant use, in part through use or review of net environmental benefit analyses conducted for past oil spills. This evaluation will include comparison of chemically dispersed oil with the fate and effects of untreated oil. As part of this study, the committee will review research on the use of dispersants during actual spills, both for surface and subsurface applications (e.g., the 2009 Montara oil spill off the Australian coast and the 2010 Deepwater Horizon oil spill in the Gulf of Mexico) to assess the net benefit of dispersant use in these cases. Specifically, the study will:

1. Assess the state of our knowledge about dispersant effectiveness (including comparisons across a range of dispersant formulations) and the fate, including short- and long-term fate, of untreated oil (no chemical dispersant applied), chemical dispersants, and chemically dispersed oil and the influence of dispersants on deposition (including marine snow) and/or transport of oil;

2. Evaluate and summarize research on the acute and chronic (sub lethal) toxicity of chemical dispersant formulations of comparable efficacy, chemically dispersed oil, and untreated oil at realistic environmental exposure levels. This will include characterization of the relative risks to wildlife health of untreated oil and chemically dispersed oil, taking into consideration exposure to volatile compounds, ingestion, and absorption of naturally versus chemically dispersed droplets;

3. Compare the benefits and limitations of dispersant application to the use of other clean-up methods (e.g. no-action, mechanical recovery, burning, and chemical herders in combination with burning);

4. Compare the relative human health risks for the use of dispersants with the use of other clean-up methods (exposure of response personnel and residents in Gulf coastal communities to oil and dispersants, and contamination of seafood);

5. Identify the research protocols and standards that would:
i) increase the applicability of lab-based measurements to the field and
ii) improve the comparability of research findings from different laboratories;

6. Assess the adequacy of the existing information to support risk-based decision-making or net environmental benefit analysis of response options under a variety of spill scenarios and recommend a "roadmap" of research and modelling to address identified information gaps.