The Garrison Diversion Project, a giant irrigation system under construction in North Dakota, threatens to pollute Canadian waters with a flow of U.S. pesticides. A Canadian coal-fired power plant planned for Saskatchewan will probably dirty the air of northeastern Montana.

These two examples were cited yesterday by Environmental Protection Agency administrator Douglas Costle to demostrate what he called "environmental interdependency."

Although economists and political scientists have long referred to the interdependency of nations for such matters as mutual security, trade and energy, environmetal protection has only recently been added to that list, Costle told a State Department conference yesterday.

"The plain fact is, pollution knows no boundaries," he said. "Pollution generated in one country inevitably affects its neighbors and often affects other nations some distance away."

During a twelve-day period in January, 1974, Costle said, acid rains from Britain, France and other countries dumped 4,000 tons of sulfate on southern Norway.

Likewise, environmental laws in one nation affect others: noise regulations restrict the Concorde supersonic transport, auto pollution laws apply to foreign cars and the new toxic substances act will control imported chemicals, Costle said.

The two-hour conference, which drew several hundered private and federal participants, was held to celebrate "World Environment Day." The speakers, including Charles Warren, head of the Council on Environmental Quality, Under Secretary of State Lucy Benson and Assistant Secretary of State patsy Mink, made no mention of the most controversial interntional environmental issue: the spread of nuclear energy.

President Carter's efforts to slow nuclear proliferation have met with hostile reactions in several foreigh countries, as have U.S. suggestions in the past that underdeveloped countries proceed cautiously with industrialization.

Such sensitivity led Warren yesterday to assert, "I do not beleive there is such a thing as the 'U.S. role' in global governmental affairs." The United States, he said, "has much to learn from other countries. Some industrialized states have living standards close to the United States but use much less energy . . .

"If there's any such a thing as a 'U.S. role' in global environmental affairs, it is this: not to assert 'leadership' in any chauvinistic or arrogant sense, but to join with our member-states of every political and economic condition as we work together to protect and renew out endangered planet."

Warren said the United States "must dramatically increase" expensive research on such international environmental problems as:

Changes in rainfall patterns during thepast few years that have caused drought around the world - so much so that some countries have discussed towing icebergs from the Arctic.

Acid rains that have caused serious economic damage through ruined crops. Scientists aren't sure where they originate.

Expolitation of the mineral resources of the oceans, while no one knows exactly how much and what minerals are there.

U.S. environmental policy is also affecting foreign aid, according to Curtis Farrar, assistant administrator of the Agency for International Development. In responce to a lawsuit brought by environmentalists, AID is decreasing the amount of pesticides it gives to developing countries, he said. Instead, the agency is informing them of problems connected with the chemicals and helping them to use biological controls instead.