"So, what is this stuff? There's a lot the public is not permitted to know about these concoctions. The EPA has published some information about them on a list of dispersants and other agents that were okayed for use in the clean-up of New Orleans after Hurricane Katrina. But a number of ingredients are listed as 'confidential' or 'proprietary', and their proportions in the mix are not disclosed.

Information provided by Nalco {they make the stuff} to EPA and the federal/BP task force on its website, known as the Deepwater Horizon Response, says that Corexit EC9527A, contains three chemicals considered hazardous:

       2-Butoxyethanol
       Organic sulfonic acid salt
       Propylene glycol

From what we can discern, the active molecule that does the dispersing is 'organic sulfonic acid salt,' a generic term for class of chemicals. Its precise chemical name is apparently proprietary. We think that once a company, or the government, or both, decides to cover the sea with this molecule, it's time to tell us what exactly it is.

The company's disclosure statement says, 'No toxicity studies have been conducted on this product'. It also says, 'Based on our hazard characterization, the potential environmental hazard is: Moderate Based on our recommended product application and the product's characteristics, the potential environmental exposure is: Low.' But how the company has reached that conclusion isn't clear.

Corexit 9500, the newer formulation, is made without 2-butoxyethanol. According to the NRC report, Nalco developed Corexit 9500 because it discovered that 'prolonged exposure to Corexit 9527 caused adverse health effects in some responders. These effects were attributed to its glycol ether solvent (2-butoxyethanol).'

Jackson told reporters that EPA permitted BP to spray the older product, Corexit EC9527A, in the early days of the spill until sufficient quantities of 9500 could be located. She described Corexit 9500 as 'more effective and more environmentally friendly.'"