The Canadian government, distressed by acid rain from U.S. industrial plants, is demanding that the U.S. negotiate an air pollution treaty.

John Fraser, Canada's new environment minister, flew to Washington last week to try to speed up discussions of the problem, which he said has become a major political issue in Ontario and other eastern provinces.

A treaty, which might require tightening air pollution standards on coal-fired power plants here, could be extremely controversial. The coal industry claims President Carter's attempts to increase U.S. coal production are hampered by overly strict air quality laws.

"Other scientists believe we've identified 48,000 Ontario lakes incapable of maintaining life within 18 to 20 years if acid precipitation continues," Fraser said after meeting with U.S. Environmental Protection Agency Administrator Douglas Costle and Interior Secretary Cecil Andrus.

"The same thing is probably happening in Quebec, New Brunswick and Nova Scotia. Acid shock going into our rivers and springs coincides with an alarming decline in salmon eggs."

Fraser estimated that 50 percent of the acid rain is caused by sulfur dioxide wafting over the U.S. border from coal-fired power plants as far away as the Ohio Valley. U.S. officials concur but add that sulfur dioxide also flows the other way, killing fish life in about 300 lakes in New York's Adirondack Mountains.

The acid rain problem, which only recently has become an issue, could alter considerably the debate over how hard the United States should crack down on sulfur dioxide emissions.

Present laws, now enforced on a state-by-state basis, do not take into account the fact that pollution travels hundreds of miles and has considerable cumulative impact. Also, present rules are designed to protect people from respiratory illness - not lakes, crops or buildings from physical damage.

"Our primary standard has been based on protecting health locally," said EPA Administrator Costle. "But increasingly, we're becoming aware that this is an ecological problem, too."

Under a treaty, new legislation might be required to tighten standards on existing power plants when the Clean Air Act is revised in 1981, he said.

While the acid rain issue could strengthen the hand of U.S. environmentalists, a treaty also could provide the critical political impetus for Canada to impose national sulfur dioxide standards. Its air pollution laws, which now vary from province to province, are weaker than those in the United States.

While acid rain is a relatively new problem in North America, it has been a controversial issue in Europe for a decade. Scandinavian countries blame British power plants for sterilizing thousands of their lakes and reducing the growth of northern forests.

A European convention to deal with such transboundary pollution is under consideration.

Fraser estimated that the United States sends about 4 million tons of sulfur dioxide to Canada each year, while Canada sends 1.2 to 1.4 million tons south. "It works both ways," he said.

"We're not coming down here wringing our hands, saying you're the culprits. We've got a joint responsibility. We don't have a heck of a lot of time to fool around."

Fraser added Canadians have been apprehensive that Carter's coal-oriented energy policy would aggravate the acid rain problem. But Fraser's talks in Washington were "extremely encouraging," he said.

"It has been made clear that President Carter has no intention of abandoning environmental concerns."

Canadians say that half a million to three-quarters of a million square miles of the Canadian Shield have been affected by acid rain. A vast rural playground of sparkling lakes and rolling green forests, the Shield includes Ontario's "cottage country," a favorite playground of millions of Canadians.

"The new government puts acid precipitation as a top priority in terms of environmental considerations," Fraser said.

The International Joint Commission, a Canadian-U.S. group that oversees enforcement of the 1909 Boundary Waters Treaty, says Great Lakes precipitation in recent years contains between five and 40 times more acid than normal. The commission estimated that lowering sulfur dioxide emissions by half would cost $350 million a year in Canada and $5 billion to $7 billion a year in the northeastern United States, which is the primary source of Canadian concern.

It added that U.S. health costs attributable to sulfur dioxide are estimated at $1.7 billion a year and architectural damage at $2 billion a year.

Carter recently acknowledged the acid rain issue in his environmental message, calling it "a major global environmental problem." He ordered U.S. agencies to draft a federal acid rain research program, working closely with Canada and Mexico.