Environmental groups in five states are suing the federal government, claiming Environmental Protection Agency rules on chemical dispersants used in oil spills do not meet clean water requirements.
The lawsuit filed Monday in Washington, D.C., claims EPA has not published a schedule that identifies where dispersants can be used and how much can be used safely.
The groups say that during the Deepwater Horizon disaster in 2010, more than 1.8 million gallons of dispersants were dumped into the Gulf of Mexico with little knowledge of the toxic effect.
EPA spokeswoman Hanady Kader says the agency just received the lawsuit and would have no immediate comment.
Three environmental groups also sued the EPA and the Coast Guard over dispersants in April, claiming the effect on endangered species was not known.
