They are using millions of gallons of this stuff to disperse the oil:

Corexit 9500:

The safety data sheet states “The potential human hazard is: High.”
According to the Alaska Community Action on Toxics, the use of Corexit during the Exxon Valdez oil spill caused “respiratory, nervous system, liver, kidney and blood disorders” in people. According to the EPA, Corexit is more toxic than dispersants made by several competitors and less effective in handling southern Louisiana crude. However, the oil from Deepwater Horizon is not believed to be typical Louisiana crude.
Reportedly Corexit is toxic to marine life and helps keep spilled oil submerged. The quantities used in the Gulf will create ‘unprecedented underwater damage to organisms.’ 9527A is also hazardous for humans: ‘May cause injury to red blood cells (hemolysis), kidney or the liver’.

Russian scientists say it will get into the rain and fall on the East Coast, causing massive unprecedented damage to microbial life, as well as being washed ashore.