The Environmental Protection Agency's chief pesticide regulator, contradicting a superior's earlier testimony, conceded to a House subcommittee yesterday that phony scientific reviews of toxic chemicals are a problem at the agency.

The conflict between Edwin L. Johnson, head of EPA's Office of Pesticide Problems, and his boss, John A. Todhunter, assistant administrator for pesticides and toxic substances, came as a House Agriculture panel ended two days of oversight hearings on EPA pesticide policy.

Johnson did not detail the extent of the problem, but said plans are under way to investigate so-called "cut-and-paste" studies of toxicology data submitted by companies seeking registration of new compounds.

In one recent case, reported this month in The Washington Post, an EPA reviewer submitted as his own work a company summary of data supporting a new product. A subsequent audit discovered that the reviewer had overlooked test data suggesting possibly adverse public-health consequences. On Tuesday, responding to a question by Rep. Steven Gunderson (R-Wis.), Todhunter assured the subcommittee that there was no problem with incomplete toxicology reviews at EPA.

He said there was no reason to be concerned about a threat to public health because of such reports.

Gunderson tried the same question again yesterday and, to the subcommittee's apparent surprise, received a far different answer.

Johnson said that he had become aware that similar cut-and-paste episodes had occurred in one division of OPP for several years and that some possible health problems in chemicals may have been overlooked.

A lengthy report by subcommittee chairman George E. Brown Jr. (D-Calif.) raised the possibility that EPA budget cuts and increased pressures to process chemical registration requests were forcing agency scientists to shortcut standard review procedures.

Johnson said his office's review of the situation means that "we have decided to go back and look at some of them," alluding to products that may have been cleared after perfunctory cut-and-paste operations.

Brown's hearings this week were a prelude to congressional reauthorization hearings later this year on the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), which governs registration procedures for agricultural and home chemical products.