A heated environmental issue facing Congress this session is the question of whether to renew, weaken or strengthen the Clean Air Act. Although the bill makes no mention of acid rain, which until the mid-'70s was not considered a major problem, scientists now warn that rain and snow carrying chemicals back to earth are raising the acidity of thousands of lakes and streams to dangerous levels. Environmentalists hope to strengthen the Clean Air Act to reduce the threat, while industry claims the problem isn't severe enough to warrant spending billions of dollars to control it. In the thick of the debate is James Galloway, an associate professor of environmental science at the University of Virginia, who has testified before Congress on the subject five times. Currently heading several national and international studies of acid rain, Galloway, 37, has collected rain samples from Bermuda to Australia, and has helped set up more than 100 rain-collection sites across the U.S. to determine just how seriously the environment is threatened. He discussed his findings with Giovanna Breu of PEOPLE.

What causes acid rain?

Sulfur dioxide and nitrogen oxides are vented into the atmosphere out of power plant smokestacks and automobile tail pipes. Those gaseous wastes react with oxygen, water and other materials to form sulfuric and nitric acids, which come down in rain and snow.

What are the consequences?

Acid rain contaminates lakes and streams so they cannot support fish. When the fish disappear, ducks, loons and predatory birds must go elsewhere. Acid rain also damages forest crops and soil. Over broad regions of North America, forests may be growing more slowly because acid rain is toxic to trees. The red spruce may be dying out because of it. It can also lead to accumulations of toxic metals such as lead and cadmium in untreated water supplies.

What other problems can it cause?

In both urban and rural areas, for example, acid rain corrosion damages iron and steel building exteriors, the paint on automobiles and houses, and landmarks such as Civil War statuary. Some estimates suggest billions of dollars in yearly damages.

Where does acid rain fall?

Most of eastern North America below Hudson Bay experiences rainfall that is from 20 to 500 times more acidic than it used to be. In 1955 only the Northeast was affected. By 1977 most of the East Coast, along with parts of northern Europe and Japan, reported acid rainfall. The Western states will have problems as they burn more coal. Already you find acid rain in the L.A. basin, primarily due to nitric oxides from automobiles. In Seattle, smelters contribute to the problem.

How does snow affect the acid content of lakes?

Areas like New England and Canada may suffer acid shock as the winter accumulation of snow melts into the lakes. Acid pollution stays in the top three feet of water. Trout species which spawn near the surface can't survive such conditions.

Can a lake be saved after it becomes highly acidic?

You can add limestone to it, but that's a temporary solution. You have to do it every year, and even liming a lake might cause ecological problems by upsetting its natural balances. If we turn down the fossil-fuel switch, it will help the lakes recover. It may take a year—or a decade.

Is any part of the environment resistant to acid rain?

Ocean water has an almost infinite capacity to absorb acids. Using this as an example, some people argue that the environment is very resilient. I disagree. The environment may have survived many changes, but we don't know how much we can damage it before it begins to damage us.

Is acid rain always man-made?

No, but the acid-making compounds that occur in nature are insignificant compared with man-made pollutants. Mount St. Helens during its initial eruption put out only about as much sulfur as one or two medium-size power plants discharge annually.

Can scientists identify the source of a particular acid rainfall?

It would be nice to be able to point to a single smokestack in Kentucky or near Chicago, but we can't do that. You could receive acid rain from a source 1,000 miles away because the wind happened to be blowing from that direction. We now find lakes with no fish a few thousand feet up in the Adirondacks because of wastes people produce in more populated areas to the West.

Do we in North America pollute only our own air and water?

If you treat North America as one big smokestack, about half its polluting material drops down on this continent, then the rest goes eastward over the Atlantic Ocean. Rain in Bermuda, downwind from the U.S., is almost as acid as on our East Coast. Even in the Arctic, visibility is greatly reduced by haze caused by fuel consumption thousands of miles away.

Has the U.S. created Canada's acid rain problem?

One study shows we put as much acid material into Canada's atmosphere as Canadians create for themselves. But it's not all one-sided, by any means. Some Canadian factories in the West pollute lakes in Wisconsin and Minnesota, and in Sudbury, Ontario, the world's largest smelter contributes 3 percent of North America's gaseous sulfur. By and large, however, we pollute Canada significantly more than it pollutes us.

What can industry do to prevent acid rain?

Some say we don't know enough about acid rain to act. Many scientists, including myself, think industry can do something to reduce acid rain and should begin now. Scrubbers, which remove sulfur from coal and oil smoke, are required by law in new factories, but many old plants need to install similar equipment, which can cost several million dollars per scrubber. Another, less costly option is to wash the sulfur from coal before burning it.

Do you recommend changes in the Clean Air Act?

We need to direct the act toward regions instead of states, since it is a regional problem, and to establish more rigid controls on hundreds, or even thousands, of pollution sources. The numbers make the job harder, but the job should still be done.

What can individuals do to help?

If enough people practice conservation and are willing to pay for cleaner energy, the acidity of rainfall will decrease. We can't put all the blame on the power companies. They're involved only because we consumers want the electricity to run our air conditioners and our electric carving knives, toothbrushes and can openers. Harris polls show that the majority of people in this country are concerned about the environment. Once we begin to act and express our opinions, maybe the government will listen to us and strengthen the Clean Air Act and keep the pollution control requirements on new power plants. We still have freedom of choice in this country. I choose a cleaner environment.