Friday, November 12, 2010

Oil spill's toxic trade-off

Dispersed oil from the Deepwater Horizon disaster could be more dangerous to wildlife than reports suggest.

Chemicals used to reduce oil slicks during the Deepwater Horizon oil spill in the Gulf of Mexico may have rendered the oil more toxic than official reports suggest, according to a Canadian toxicologist.

Peter Hodson, an aquatic toxicologist from Queen's University in Kingston, Ontario, presented his case on 9 November at a meeting of the Society of Environmental Toxicology and Chemistry in Portland, Oregon, in a session that highlighted the uncertain effects of such treatments on marine wildlife.

The chemicals, known as dispersants, are used to reduce the surface tension of spilled oil, allowing wind and waves to break it 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.

Danger dispersed?

But until it is degraded by such bacteria, the dispersed oil becomes mixed into the water rather than sitting on top of it. This means that its toxic constituents, most notably polycyclic aromatic hydrocarbons (PAHs), are likely to have a greater effect on marine wildlife. "It's definitely a trade-off," says Charlie Henry, the National Oceanic and Atmospheric Administration's lead scientific support coordinator for the emergency response to the oil spill.


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