Scientists and ocean advocates stepped up warnings this week of potential dangers from chemical dispersants, as oil giant BP released unprecedented amounts of a classified and toxic chemical to thin the Gulf of Mexico oil slick before it reaches shore.
"Unfortunate recent events in the Gulf Coast have once again brought to the forefront issues pertaining to the impacts of dispersants and dispersed oil," Carys Mitchelmore, a researcher at the University of Maryland Center for Environmental Science, told the Senate Subcommittees on Oversight and Water and Wildlife.
"There's a potential for a toxic soup of unknown effects, which cannot be predicted even if the individual constituents are known."
Response teams have dumped about 436,000 gallons of a chemical dispersant, called Corexit, into the Gulf to battle the leak from BP's sunken Deepwater Horizon ruptured rig—more than has ever been used in the United States.
Some of that is being pumped 5,000 feet underwater at the site of the spill, a deepsea technique that has never been tried. The exact ingredients of chemical dispersants are protected as trade secrets and are unknown.
"Putting this right on the seabed, it's unknown what the consequences will be," said Mitchelmore.
The dispersant, a detergent-like brew of solvents, surfactants and other compounds, breaks down oil into tiny particles that scatter into the sea to prevent crude from washing ashore and wiping out wildlife.
Some analysts describe the chemical stew as a a slow and silent killer, however, quietly altering the balance of food webs, contaminating species and damaging the overall health of the oceans.
John Everett, president of Ocean Associates Inc., a Virginia-based oceans and fisheries consulting firm, said the dispersant could cause more harm than the calamitous spill itself, which is gushing oil at a pace of 210,000 gallons a day and has now exceeded the four-million gallon mark.
"The oil damage will eventually heal. Better procedures will be employed and this oil will be recycled and assimilated," Everett told Congress.
"The flow of chemical materials into our waters is another matter. There are too many insidious contaminants entering our estuaries, causing genetic harm and poisoning our Earth, turtles and seafood."
The harmful chemicals, he said, creep into the food supply and "directly impact us as well."
Soon after the April 20 oil rig blast, U.S. Environmental Protection Agency (EPA) and the U.S. Coast Guard gave BP the greenlight to spray the dispersant on the water's surface and to test it almost a mile under the sea. The chemical was pre-approved for use in the National Contingency Plan (NCP) Product Schedule.
EPA declares that it has "not given authorization for the full scale use of dispersants underwater beyond initial tests to determine its effectiveness." But that could soon change.
EPA Administrator Lisa Jackson told reporters on Wednesday that so far 28,709 gallons of dispersants had been discharged in the seabed for testing purposes. Jackson said the agency is now waiting on results to determine the chemical's effectiveness in decomposing crude at those depths. Two earlier attempts to test the site failed, she said.
"The effect of underwater dispersant still is unknown," Jackson added.
Working with EPA, National Oceanic and Atmospheric Administration (NOAA) said it was examining water samples on the seafloor near the leak.
On the sea surface, the results of EPA's most recent water samples, gathered from April 30 to May 5, showed that "water quality does not pose increased risk to aquatic life."
Speaking to the subcommittees this week, Jim Jones, deputy assistant administrator for the EPA's Office of Chemical Safety and Pollution Prevention, conceded that the dispersant being deployed "has toxicity associated with it" and that "damage has been done."
He called the tests an "environmental trade-off" between long-term harm to offshore wildlife and fragile lands if the spill were to wash ashore, and potential shorter-term damage to some sea life.
Mitchelmore, said the trade-off is simply the "protection of one habitat...at the cost of another."
"In this case, the protection of shoreline species at the expense of organisms residing in the water column and potentially also those at the seabed," she added.
In regard to Corexit, Mitchelmore said, "limited prior toxicological information exists to fully assess risks to exposed organisms."
But both oil and oil spill dispersants are known to cause a variety of health effects in animals, she added, "including death and a variety of sublethal impacts including reduced growth, reproduction, cardiac dysfunction, immune system suppression, carcinogenic, mutagenic and teratogenic effects and alterations in behavior."
Jackson said that Corexit is at most one-tenth "as toxic as oil."
Fishing advocacy groups, meanwhile, such as the eight-state Southern Shrimp Alliance (SSA), are fearful of long-lasting effects of a chemical that could eat away at their livelihoods.
"SSA welcomes testing sediments in the water column as a good first step, but fear the 'act now, check later' approach being taken with dispersants," said John Williams, the group's executive director. "These chemicals relocate the oil from the shores to the water column where it will be spread by currents to vital reproductive grounds throughout the western Gulf of Mexico."