Environmental Protection

Deepwater Horizon Burns Emitted Low Levels of Dioxin, EPA Reports

The U.S. Environmental Protection Agency released two peer reviewed reports concerning dioxins emitted during the controlled burns of oil during the Deepwater Horizon BP spill. The reports found that while small amounts of dioxins were created by the burns, the levels that workers and residents would have been exposed to were below EPA’s levels of concern.

Dioxins are a category that describes a group of hundreds of potentially cancer-causing chemicals that can be formed during combustion or burning.

Controlled burning of oil on the surface of the ocean (also called in situ burning) was one method used by the Unified Command during the Deepwater Horizon BP oil spill, to reduce the spread of oil and environmental impacts at the shoreline. A total of 411 controlled burn events occurred of which 410 could be quantified, resulting in the combustion of an estimated 222,000 to 313,000 barrels of oil (or 9.3 to 13.1 million gallons).

With support from the U.S. Coast Guard, EPA conducted sampling of emissions at the source of the controlled burns in the Gulf of Mexico to determine if dioxins were present. The sampling was conducted to identify potential dioxin exposures and determine the potential risks from inhalation to workers in the vicinity of the fires, risks from inhalation to the general population and risks to the general population from consuming fish caught in the area.

The first report summarizing EPA’s sampling effort indicates that while dioxins were created from the burning of oil on ocean water, they were created at low levels – levels similar to the emissions from residential woodstoves and forest fires.

The second report, co-authored with scientists from the National Oceanic and Atmospheric Administration, presents the results of a screening risk assessment for the dioxins emitted from the controlled oil burns. The results indicate that increased cancer risk due to exposure to the dioxins released from the controlled burning of oil was small ─ less than a 1 in 1,000,000 increased cancer risk. Additional cancer risks for inhalation by workers and onshore residents and fish consumption by residents were lower than risk levels that typically are of concern to the agency. Typically, the agency has a concern when the risk is greater than 1 in 1,000,000.

Had the spill of oil continued, the results of these measurements would have been used by the Unified Command to determine if burning should continue. However, the well was capped on July 15, and the last in situ burn occurred on July 19. Consequently, these results are most useful to inform and improve the agency’s ability to respond to future oil spills.

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