Midwest Republicans yesterday launched a sharp counterattack on Canada over acid rain responsibility, charging at a congressional subcommittee hearing that U.S. control of air pollution is already much stricter than Canada's and does not need stiffening.

The Canadians had come to the House Energy subcommittee on health and the environment to say that "an enormous number of dying lakes" in eastern North America argue conclusively for more controls on sulfur and nitrogen emissions as Congress rewrites the 1970 Clean Air Act.

Using slides and film in a dimly lit hearing room, Canadian government spokesmen said 10 years of research showed that half of Canada's acid rain comes from U.S. sources.

Other toxic chemicals are airlifted across the border as well: ozone that can break down rubber and plastics, and oil particles containing cancer-causing PCBs.

The Reagan administration call for further research is not enough, said J.P. Bruce, assistant deputy minister of Canada's Atmospheric Environment Service. "This is a bit like waiting to treat a cancer patient until we have the perfect cure," he said.

Rep. Clarence J. Brown (R-Ohio) quoted from a study by the Congressional Research Service of the Library of Congress showing that U.S. air pollution controls include compliance deadlines, state plan and enforcement requirements, stiffer automobile emission limits and fewer options than Canadian law. "The Canadian law appears to lack muscle," he said.

He noted that the new Canadian National Energy Plan would construct power plants along the U.S. border, presumably to export power, even as Canada asks that coal use in U.S. utilities be curbed. That, he said, raises "a number of questions regarding other motives" for the Canadian position.

The Canadians responded with a history lesson on the British-Canadian tradition of less-formal written enforcement procedures.

"What's important is what comes out of the stack. That's where you see that the law works," said Canadian Embassy environment counselor George Rejhon.

Rep. Edward R. Madigan (R-Ill.) joined the attack, complaining that the Canadian film showed only U.S. air moving north and never Canadian air moving south. "Then you might see all that pollution going the other way," he said.

In the Senate yesterday, Sens. John H. Chafee (R-R.I.) and George J. Mitchell (D-Maine) introduced bipartisan legislation to freeze U.S. sulfur dioxide emission limits and then reduce it over the next decade in 31 states east of the Mississippi, a move the Reagan administration is sure to oppose. Sen. Robert T. Stafford (R-Vt.), chairman of the committee rewriting the Clean Air Act, joined as co-sponsor.

The acid rain debate came close to being an international incident last week, when the Canadian Embassy canceled the Canadian officials' appearance, saying Canada was reluctant to become involved in U.S. domestic policy debate.

The testimony was rescheduled after opposition Conservatives charged that the government appeared to be caving under pressure from the Reagan administration.

Canada's testimony followed a National Wildlife Federation report Monday that 15 eastern states, led by Massachusetts, are "extremely vulnerable" to acid rain damage, while 10 others face moderate threats.

"It can't be long before every state in the union is affected," said federation President Jay D. Hair.