h/t Mugsy:

As if the dispersants themselves weren't toxic enough, the 1.8 million gallons of Corexit 9500 (oil dispersant) sprayed on BP's spill in the Gulf of Mexico breaks down the oil, releasing some of the most toxic chemicals already in the oil into the water, dramatically increasing the toxicity of the spill.

From NBC News Scientists: BP dispersants have made spill more toxic:

Amid growing concern about the use of dispersants in the Gulf of Mexico, a group of scientists working for law firms suing BP says their testing indicates that the dispersants being used to break up the oil are making this spill even more toxic to marine life.

Dr. William Sawyer, a toxicologist, is part of a team of scientists hired by law firms — led by Smith Stag of New Orleans — that are representing Louisiana fishermen and environmentalists.

The scientists collected and analyzed globs of oil, sand, and water from more than a dozen sites in four states along the Gulf.

Sawyer told NBC News that the findings are troubling. "We now have compelling evidence that the dispersant has enhanced and increased the toxicity from the spill," he said.

Last week, a group of independent scientists called for an "immediate halt" to the use of dispersants. In what was called a "consensus statement," they warned that dispersants pose "grave risks to marine life and human health." Read on...