WASHINGTON — Scott Pruitt, the head of the Environmental Protection Agency, stripped a half-dozen scientists and academics of advisory positions Tuesday and issued new rules barring anyone who receives E.P.A. grant money from serving on panels that counsel the agency on scientific decisions.

The move will effectively bar a large number of academic researchers, many of them experts in fields ranging from toxicology to epidemiology, from advising the E.P.A. on scientific matters, since the agency is one of the largest funders of environmental research.

Mr. Pruitt was expected to appoint several industry representatives to the panels. He did not impose any new restrictions to prevent them from offering advice on environmental regulations that may affect their businesses.