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<\/a>In April 2010, an explosion rocked the Deepwater Horizon oil rig, causing a fire and the spill of as much as 7.8 million liters of oil. Photo by Science History Images\/Alamy Stock Photo<\/p><\/div>\n
\u201cI was a healthy son of a bitch before,\u201d he says, in a Louisiana drawl. \u201cI could run my boat by myself. Now, I need one or two deckhands. I have half my breathing capacity.\u201d<\/p>\n
Barisich is angry at BP for the oil spill and the subsequent use of a commercial product called Corexit. Corexit is one of the best-known dispersants, a class of chemicals formulated to break up oil slicks in the ocean. During the Deepwater Horizon cleanup, a record 6.8 million liters of Corexit were dumped into the Gulf.<\/p>\n
Even before 2010, scientists were raising concerns about Corexit\u2019s safety and efficacy. A decade later, there is even more evidence against dispersants like Corexit, yet they remain a key tool for oil spill responders in jurisdictions around the world.<\/p>\n
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For oil spills at sea, cleanup crews rely on four main techniques: contain and slow the oil spread with booms, collect what they can with boats that skim oil off the surface or with absorbent pads that soak it up, burn the oil on the water, or sink it with chemical dispersants. The choice of which to use depends on many factors, including the type of oil, weather and sea conditions, proximity to sensitive habitat, and resources available. Crews often use more than one technique at the same time. Each has pros and cons, but none is as controversial as the chemical dispersants.<\/p>\n
In the Gulf, crews applied dispersants to break up surface slicks and reduce the chances of oil contaminating coral reefs or marshes or impacting surface-dwelling animals. Usually applied from the air, the chemicals are mixed with the floating oil by wind and waves, breaking the cohesive slick into microdroplets that disperse through the water column in parts per million or even per billion.<\/p>\n
But it\u2019s a trade-off. Dispersants contain chemicals that are considered toxicants, and they impact natural oils, too, like the ones on human skin. The dispersed oil is more likely to impact ecosystems below the surface and at the seafloor.<\/p>\n
That\u2019s why organizations and companies tasked with preparing for marine oil spills carefully plan where and when to use dispersants, says Matthew Sommerville, a member of the executive committee of the nonprofit International Spill Control Organization. For example, a regional cleanup plan would include advice to avoid applying dispersants near coral reefs, spawning fish, nesting birds, or migrating marine mammals or in situations where currents would carry them toward sensitive areas, and to apply them only in the right weather conditions, when they can be effective.<\/p>\n
The advice stems from the checkered history of dispersants. The first documented use of a chemical mixture, an earlier version of Corexit, was after the 1967 Torrey Canyon<\/em> spill off England\u2019s coast. Even then, scientists had concerns about the toxicity in the marine environment, prompting governments to develop new guidelines for use and push for less harmful formulations. Yet, over the years, dispersants crept into the toolkit of most spill response organizations around the world.<\/p>\n Within days of the Deepwater Horizon spill, crews sprayed dispersants on the growing slick from boats, helicopters, and airplanes. But because the oil was spewing out of the seafloor, BP asked for permission to apply Corexit at the wellhead. The US Environmental Protection Agency (EPA) and the US Coast Guard approved the idea, and in an experimental effort, cleanup crews injected the dispersant 1,600 meters under the water surface in an effort to disperse the oil before it hit the surface.<\/p>\n