For Kenneth Borst, waterways like the Perry Healy Brook are where he would rather fish for trout than for facts. The brook courses through a viridescent woodland about a mile north of the Atlantic coast in an area of beauty that has been home to the Narragansett tribe for centuries. Acid rain is destroying Perry Healy Brook.

Late the other afternoon, Borst, a professor of chemistry at Rhode Island College for the past 22 years, took a visitor a hundred yards off a backwoods road to a bend in the brook. A fallen log extended across the five feet of water. In his hand, Borst held a chartbook in which one page was devoted to the acidification findings of a citizen who monitors the brook.

For the past yea, Borst has been the leader of an environmental project that regularly samples water from 38 streams and ponds in Rhode Island. Two of the 38 are acid dead. Eleven, including Perry Healy, are critical. Nineteen are endangered.

Borst, a fisherman who throws back his trout "because they are too valuable to be caught only once," lingers in the woods to talk about the scourge of acid rain: "Looking at this from a Rhode Island point of view, we're being dumped on, in plain language. Ohio is the principal culprit. Its plants are the biggest supplier of acid rain here. It would be nice if we could say, 'Ohio, clean up your dirt,' but it won't happen. The utilities and lobbies will cry that it's too costly."

The cry has been heard for years. So has another one: More study is needed. Borst and his volunteers took that to heart by taking to the woods. They learned locally what has been well documented nationally -- that acid rain, which is mostly oxides of sulfur and nitrogen, is a threat that is getting worse each year.

It isn't only waterways and forests. A new study from the Environmental Protection Agency and the Army Corps of Engineers reports that acid rain is corroding buildings. It found that about $5 billion worth of structural damage in 17 states occurs annually.

Last October President Reagan promised to "continue as fast as we can with research" on acid rain. Speediness isn't needed. The research was on hand when Reagan came to office. It was in 1980 that the public began learning about acid rain from the studies done in the 1970s. Five years ago, the Adirondacks of New York were a disaster area of lakes turned sterile by acid rain. Part of the reaction then was: what's the uproar? It's only a few fish. That echoed the line from the oil spills of the 1970s: it's only birds.

The devastation of acid rain begins with the killing of algae and plankton, natural fish foods. The fish are food for such wildlife as otter, mink and waterfowl. While the fish die and the animals starve, tree and crop growth are slowed. And now, with buildings being damaged, the question is, what's next?

Clean air, once thought to be free like the moon and stars, is now known to be costly beyond anyone's earlier estimates. In 1980, the Audubon Society of Rhode Island pledged to "insist that the controls on acid-emitting industries be tightened, and understand that there will be a continuing economic price for this. It is not, and will not be, easy to convince most people that anything is happening when they can't see it and the industrial and job market is immediately affected by controls."

Congress is among the unconvinced. In this session, two acid-rain control bills were introduced in the Senate and House. One required that sulfur-dioxide emissions be reduced by 10 million tons over a 10-year period, the other by 8 million. Both bills were defeated. Enough aci can be found in streams of Rhode Island to load batteries of every limousine on Capitol Hill, but the political power of the utilities remains greater than that of the environmentalists.

In the courts, six northeastern states brought suit against EPA to require polluting states to reduce their emissions. The Clean Air Act, taken lightly by EPA, provides relief for states wanting to protect themselves from pollution that floats in crosswind. In late July, a federal judge ordered the agency to obey the law.

The news this summer is the confirmation that acid rain isn't only a curse on New England. Lakes in the Rockies, Sierras and Cascades have been declared vulnerable to poisonous emissions from smelters up to 600 miles away. Florida's lakes were found to have high acidity.

None of that surprises Prof. Borst. He has been saying all along that the expenses of stopping acid rain must be shared by the whole nation. Tiny Rhode Island, the worst hit, ought to be among the first to get relief.