British Petroleum and government disaster-relief agencies are using a toxic chemical to disperse oil in the Gulf of Mexico, even though a better alternative appears to be available.

As the Deepwater Horizon oil spill spreads, BP and the U.S. Coast Guard have conducted tests with Corexit 9500, a chemical designed to break oil slicks into globules that are more quickly consumed by bacteria or sink into the water column before hitting shore.

The decision has been a controversial one. A few scientists think dispersants are mostly useful as public relations strategy, as they make the oil slick invisible, even though oil particles continue to do damage. Others consider Corexit the lesser of two evils: It’s known to be highly toxic, adding to the harm caused by oil, but at least it will concentrate damage at sea, sparing sensitive and highly productive coastal areas. Better to sacrifice the deep sea than the shorelines.

[Just wait until a hurricane stirs it up and pushes it to shore]

But even as these arguments continue, with 230,000 gallons of Corexit on tap and more commissioned by BP, a superior alternative could be left on the shelf.

Called Dispersit, it’s manufactured by the U.S. Polychemical Corporation and has been approved for use by the Environmental Protection Agency. Both Corexit and Dispersit were tested by the EPA, and according to those results, Corexit was 54.7 percent effective at breaking down crude oil from the Gulf, and Dispersit was 100 percent effective.

[So why are they using the chemical that is less effective and more toxic?]

Not only did Corexit do a worse job of dispersing oil, but it was three times as lethal to silverfish – used as a benchmark organism in toxicity testing — and more than twice as lethal to shrimp, another benchmark organism and an important part of Gulf fisheries.