Washington (CNN) -- Government scientists studying the use of chemical dispersants to combat the Gulf of Mexico oil spill told lawmakers Wednesday that the chemicals have not increased the overall level of toxicity in the Gulf.
The researchers, who were testifying before a joint congressional committee, asserted that seafood from the Gulf is safe for human consumption.
They warned, however, that more research and monitoring needs to be done.
Sen. Sheldon Whitehouse, D-Rhode Island, said the use of 1.8 million gallons of dispersant -- the most ever used in response to a single incident in the United States -- was "a grand experiment."
"It is unclear if this will limit the damage or cause even greater harm," he asserted.
BP, with the approval of the federal government, applied the dispersants to break up the oil before it reached sensitive ecosystems along the shore of the Gulf. About 780,000 gallons were applied miles beneath the sea to break up the oil as it gushed from the damaged well.
Assistant EPA Administrator Paul Anastas said Wednesday that the agency recognizes there are "environmental tradeoffs" in using dispersants. But he insisted the agency has found no evidence of the chemicals remaining either in the Gulf waters or on shore.
Earlier this week, the agency released new data showing dispersants, even when mixed with oil, are no more toxic than the oil itself. However, Anastas added, "The crisis has made it evident that additional research is needed."
The EPA has launched a $2 million study on both the short- and long-term effects of these chemicals on humans and the environment.
Pressed by lawmakers on the effects of the chemicals on the food chain, David Westerholm of the National Oceanic and Atmospheric Administration said his agency has been testing seafood from the Gulf and, to date, "seafood reaching the marketplace is safe to eat."
Anastas later told CNN that "we are seeing no evidence of dispersants in the food chain, and while continued monitoring is needed to ensure that this doesn't change, we have no data to suggest that it will."