Environmentalists battling to curb acid rain think they could get a substantial boost this week from an unexpected quarter - the US Environmental Protection Agency.
Monitor writer Rushworth M. Kidder reports that Science Trends newsletter has obtained a 1,200-page EPA research report purporting to show that the acidification of lakes in eastern Canada and the eastern United States results from increased sulfur dioxide emissions from coal-burning utility plants in the Midwest. The report will be made public later this week.
Newsletter editor Arthur Kranish says the report ''cites with approval'' studies showing that atmospheric pollutants can travel hundreds of miles before they are deposited in liquid or solid form.
He also quotes the report as saying that acidification of surface waters ''cannot be attributed to land-use changes,'' challenging the view that acidification results from more local causes such as automobile exhaust.
But Courtney Riordan, the EPA's acting assistant administrator for research and development, says that interpretation of the report is ''off the mark.'' He says he saw earlier drafts of the EPA report, which was written by more than 50 scientists under contract with the agency, and that it reveals ''nothing new or earthshaking.''
When the document is finally approved, he says, he expects the summary to say that ''basically we don't know the answers right now, and we'll have to spend more money finding out.''
Canadian officials in Ottawa, not having seen the report, declined comment. The Canadians have blamed the EPA and the Reagan administration for failing to clamp down on US polluters. But EPA officials fault the Canadians for demanding expensive control measures without having conclusive proof that acid rain results from utility-plant emissions.