The Environmental Protection Agency yesterday lost one lawsuit, settled another by negotiation and had a third filed against it. All involved environmental groups accusing the EPA of failing to take proper regulatory action.

In the first case, the U.S. Circuit Court of Appeals here ruled that the agency acted illegally in 1981 when it delayed the adoption of standards for hazardous-waste incinerators and storage facilities.

The EPA began putting the rules into effect last year, after the Environmental Defense Fund filed suit.

But the court elected to decide the issue anyway, for its value as a precedent. "EPA's history of deferrals and suspensions . . . show such conduct may reasonably be expected to occur again," the 2-to-1 ruling said.

In the out-of-court settlement, negotiated with the Natural Resources Defense Council and a coalition of other groups, the EPA agreed to act within 18 months on lead-control plans for 27 states and the District of Columbia.

The states were supposed to have plans for dealing with airborne lead by November, 1979.

Meanwhile, the National Wildlife Federation and its Colorado affiliate sued the EPA in U.S. District Court in Denver, contending that the agency has fallen down on the job of protecting underground sources of drinking water from contamination by deep-well injection of hazardous wastes.