The Environmental Protection Agency announced yesterday job changes by seven senior career employes, including three of the highest-ranking officials in the Superfund and hazardous-waste disposal programs.

Administrator Lee M. Thomas said the unusual swaps were designed to infuse "new blood and fresh ideas" into the agency's programs. But the management overhaul was greeted with skepticism by industry representatives and environmentalists, who called it "ill-timed" and warned that it could hamper the agency's ability to meet its expanded responsibilities for toxic waste.

The job switches, which will be phased in over the next three months, include:

* John Skinner, director of the Office of Solid Waste, will move to the agency's research division. His deputy, Mike Cook, will head the drinking-water program. The Office of Solid Waste enforces federal toxic-waste disposal laws and was given major new duties when Congress rewrote the law last year. The drinking-water program is expected to get expanded duties this year.

* Bill Hedeman, who has headed the Superfund office nearly as long as Superfund has been in existence, will be transferred to the water division, swapping jobs with Henry Longest, who has been acting head of the agency's water programs. The changes in the Superfund program come as Congress is debating a major expansion of the toxic-waste cleanup law.

* Vic Kimm, director of drinking-water programs, will assume new duties in the Office of Pesticides and Toxic Substances. He will replace Marcia Williams, who will move over to Skinner's job in the solid waste office.

* Ron Brand, a member of the policy staff, will take a new post -- director of programs to control leaking underground storage tanks.

The changes in the Superfund and hazardous-waste offices come a day after the Senate confirmed J. Winston Porter as head of that division and will leave open Cook's job as deputy director of hazardous-waste disposal.

In a memorandum to the agency's employes, Thomas said he thinks that the changes would "help bring valuable cross-media perspectives to our decision making."

But some outside the agency took a dim view of the latest game of musical chairs. "From my neck of the woods, it means that the people who know the most about the regulatory program will not be there to run it," said David Linnett of the Environmental Defense Fund. "There won't be any institutional expertise. Who's going to brief whom?"