Queen's University

Environmental Protection Agency ‘sugar-coating’ risks posed by Gulf oil spill


The risks to fish of the chemical dispersants used to break up slicks during the Gulf of Mexico oil spill may have been greater than reported to the public, according to new research from a Queen’s University professor.

Peter Hodson, a Biology and Environmental Studies researcher who is an expert in fish toxicology, says that the Environmental Protection Agency (EPA) has been misleading the public when it says the oil-dispersant mix resulting from the Gulf of Mexico spill is no more toxic than the oil itself.

"EPA has presented data only on toxicity, which is just part of the risk equation," Dr. Hodson says. "By not considering the effects of dispersants on exposure to oil, they have sugar-coated the message. To understand the risks of treating oil with chemical dispersants, we need to understand that oil dispersed in the water column of the Gulf of Mexico exposes marine fish to far more toxic chemicals than oil just floating on the surface."

His research found that fish embryos are easily affected by dispersed oil. Exposures as brief as an hour can greatly impact embryonic fish. Because some fish species may spawn during an oil spill, the risk is that a toxic plume of dispersed oil could destroy an entire year’s hatch.

The dispersants allow wind and waves to break oil floating on the water’s surface into microscopic droplets. These droplets disperse through sea water rather than floating in massive oil slicks that can blow on to shorelines. They are also more easily attacked by oil-eating bacteria. But until it is degraded by such bacteria, the dispersed oil droplets that are mixed into the water release chemicals that are toxic to fish and other aquatic species.

The dispersed cloud of microscopic oil droplets contaminated a volume of water 100 to 1,000 times greater than if the oil were confined to a floating surface slick. This greatly increases the exposure to marine wildlife.

Dr. Hodson presented his findings at a meeting of the Society of Environmental Toxicology and Chemistry in Portland, Ore.

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Last updated at 12:12 pm EDT, Fri August 29, 2014
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