Toxic Oil Dispersants Linger in Gulf of Mexico

February 2, 2011- Nick Engelfried

Soon after oil started gushing from the floor of the Gulf of Mexico in the wake of the BP Deepwater Horizon explosion, BP and the US Coast Guard began injecting thousands of gallons of chemical dispersants into the affected area in an effort to break up toxic oil plumes.  However these synthetic compounds came with their own environmental impacts, many of which remain not fully known.  Now new evidence suggests dispersants that were supposed to soon break down and disappear in fact remained in the Gulf waters at least until last September.

The main dispersant used on the BP spill is Corexit, a chemical manufactured by the Naco Holding Company (NHC).  This Illinois-based company has financial ties to BP itself, and BP has consistently insisted on using NHC’s product rather than other types of dispersants.  For months scientists were prevented from adequately predicting the effects of Corexit on the environment because the exact composition of the compound is a trade secret of NHC.  Bowing to environmental concerns, in May of 2010 the US Environmental Protection Agency ordered BP to greatly reduce the frequency with which Corexit was used and to find less toxic alternatives.

Despite the EPA directive, BP kept applying Corexit heavily with the Coast Guard’s blessing.  According to US Representative Ed Markey (D-MA), BP continued using between 6,000 and 10,000 gallons of Corexit on the Gulf of Mexico every day even after the mandate to reduce its application.  The Coast Guard did not object to the practice and in fact authorized it.  In all about 800,000 gallons of Corexit were used on the BP spill in the spring and summer of last year. 

To determine whether or not Corexit was lingering in the environment, researchers form the University of California at Santa Barbara sampled the waters around the BP oil spill for a period of time between May and September of 2010.  The scientists tested water samples for the chemical DOSS, an active ingredient in Corexit.  They detected DOSS in the oil plume throughout the duration of the study, and found it had not broken down as rapidly as hoped. 

In laboratory tests Corexit has been judged dangerous to humans and other organisms.  Exposure to Corexit can result in liver and kidney damage as well as nervous system depression.  Safer dispersants on the market include Dispersit, a water-based compound produced by the company Polychem.  As part of its May directive the EPA instructed BP to consider using a safer product like Dispersit, but the oil company declined to do so. 

The active ingredients in Corexit may not have broken down as BP predicted they would, but one thing the dispersant succeeded in doing was causing oil plumes to sink near the bottom of the Gulf of Mexico.  This likely prevented more oil from washing up on coastlines, but is not necessarily good news for marine organisms.  In fact some scientists worry Corexit may simply have guided vast quantities of oil into deepwater habitats that are now being exposed to the toxic effects.  Fish and invertebrates of the deep ocean are often exquisitely adapted to a very specific environment, making them especially vulnerable to disturbance.  The full impacts of oil on the deep waters of the Gulf are not completely known at this point, but last November researchers discovered a mass die-off of deep sea coral caused by sinking oil plumes. 

In fact it will probably by months or years before the full effects of dispersants on the BP oil spill are fully understood.  New findings are likely to emerge surrounding the effects of Corexit and sinking oil plumes on marine life and the undersea environment.  However the most recent research shows active ingredients in oil dispersants may remain in the water for much longer than realized, calling into question what unintended consequences their use will have on the Gulf of Mexico and the coastal economies which depend on it.

Photo credit: Jim Greenhill

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