Dispersant 'may make Deepwater Horizon oil spill more toxic'

Deepwater Horizon oil rig spill
Oil blobs and sheen remain in the waters of Chandeleur Sound, Louisiana. Illustration: Eric Gay/AP [This caption was amended on 6 May 2010. The original caption sited Chandeleur Sound 'near Los Angeles'.]

Chemicals used to break up the Deepwater Horizon oil spill before it reaches shore could do lasting damage to the waters of the Gulf of Mexico, environmental scientists say.

By BP's own account, it has mobilised a third of the world's supply of dispersant, so far pouring about 140,000 gallons (637,000 litres) of the cocktail into the Gulf as of today. Some of the dispersant has been injected directly into the source of the spill on the ocean floor, a technique never deployed before, deepening concerns about further damage to the environment.

The dispersants are designed to break down crude into tiny drops, which can be eaten up by naturally occurring bacteria, to lessen the impact of a giant sea of crude washing on to oyster beds and birds' nests on shore. But environmental scientists say the dispersants, which can cause genetic mutations and cancer, add to the toxicity of the spill. That exposes sea turtles and bluefin tuna to an even greater risk than crude alone. Dolphins and whales have already been spotted in the spill.The dangers are even greater for dispersants poured into the source of the spill, where they are picked up by the current and wash through the Gulf.

The high demand for dispersant carries an additional risk. As BP runs through stocks of the chemical, called Corexit, scientists fear it will fall back on older stockpiles in the developing world that are more toxic than those approved for use in the US. "You are trying to mitigate the volume of the spill with dispersant, but the price you pay is increased toxicity," said Richard Charter, a scientific adviser to Defenders of Wildlife. "There are no good answers in a mess of this size."

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