Washington — Ten years ago, on bad days, the Potomac River stank like an old sneaker. When the wind was right, you could smell it from the White House. President Nixon, on occasion, would ring up the Environmental Protection Agency and ask what was being done about ''that awful odor.''
Today, the river is clean enough for rockfish and walleyes. Oxygen in the water has doubled, and pollutants such as phosphorous have been almost scrubbed away.
The Potomac ''really is a model environmental success story,'' says David Loveland, a District of Columbia water planner. ''The world record carp was caught here last year: 57 pounds, 13 ounces.''
But during storms, raw sewage flows into the river from 50 overflow pipes. Runoff - pollution washed from farms and city streets - is still troublesome.
Thus Washington's riverfront is a symbol of the state of the United States environment. Much has been done to clean up our air and water - but troubling pollution problems remain.
Today's environmental villains are particularly tough customers. The problems associated with acid rain, toxic waste, and runoff are widespread, not fully understood by scientists, and difficult to solve. Cleaning them up will cost billions.
''These things are harder to deal with than we realized in the '70s,'' says William Reilly, president of the Conservation Foundation.
The fact that the country is ready to attack them, however, represents a major change. Two decades ago, ''environmentalists'' were a fringe group of US society, people who wore Earth Day T-shirts and unusual sandals. Today, in a sense, almost everybody is an environmentalist. Polls consistently show that a majority of the US population now supports strong environmental laws.
Last year, an ABC News/Washington Post poll found 75 percent of respondents strongly backed environmental programs. Fifty-eight percent of the people who responded to a New York Times poll in 1983 said the US must continue to make environmental progress, regardless of cost.
Congressional debate on environmental programs is now remarkably different than it was in the early 1970s. The question is no longer whether the programs should exist at all, but how extensive they should be.
''Environmental policy has been a tremendous success in the context of a democratic society. We have fought battles and come up with solutions that work pretty well,'' says Kent Gilbreath, a Baylor University associate dean and an expert in environmental economics.
The first wave of environmental laws, passed a decade ago, focuses on what are today called ''conventional pollutants.'' These substances are tangibly nasty; they smell, bubble, obscure the sun, or adhere to birds' feathers. Airborne sulfur dioxide, carbon monoxide, and lead are regulated by the Clean Air Act, for instance. The Clean Water Act controls oil, human waste, and solids suspended in lakes and streams.
These early laws, for the most part, attacked easily identifiable polluters such as factories and power plants. And they attacked successfully. In the last 10 years, the US has made great progress in cleaning up its environment.
The air quality in large cities, as measured by the pollution standards index , has improved dramatically. In 1974, residents of an average urban area had to breath unhealthy air some 66 days a year. Today the figure is 33. Nationwide, the amount of carbon monoxide in the air has been cut 27 percent since '74. Airborne particles are down 58 percent since that time.
Much US surface water has also been cleansed. The Great Lakes are reviving; Atlantic salmon are returning to the Maine's Penobscot River. Oil spilled into lakes and streams has been reduced 71 percent since the '70s; phosphates, 74 percent. These figures are no reason for complacency, however. The quality of some streams and many lakes, the Conservation Foundation warns, ''appears to be degrading.''
Overall, the US can be proud of its cleanup record. Public environmental policy today, however, is marked not by satisfaction but by confusion. Major environmental laws that have expired and need to be reauthorized, such as the Clean Air Act, are stalled in Congress. New issues, such as acid rain, are pinned down in political battles remarkable for their complexity.
On the environment, ''the country seems to have paused to catch its breath,'' concludes a recent report from the President's Council on Environmental Quality.
Part of this confusion is a legacy from the days of James Watt, former Interior secretary, and Anne Burford, former administrator of the Environmental Protection Agency (EPA). This pair's controversial actions and ''Ride of the Valkyries'' confrontational style polarized environmental politics, say congressional aides.
Much of today's uncertainty, however, stems from the fact that the US is now addressing a second wave of environmental issues, problems that will be much harder to solve than those the country tackled in the '70s.
This second wave of problems centers on ''toxics,'' dangerous substances - dioxin, benzene, ethylene dibromide (EDB) - that are hard to track and capture.
''Despite our success in reversing the most obvious insults to air and water quality over the past 13 years, we still face enormous challenges,'' EPA administrator William Ruckelshaus noted in a recent letter to an environmental group.
Acid rain is probably foremost among pollution issues for the '80s. The Sierra Club has made lobbying for acid rain legislation a top priority.
Acid rain represents ''the kind of problems we're going to increasingly have, '' says the Conservation Foundation's Mr. Reilly. ''It's not (caused by) a single source. We don't truly understand its causes, or even its effects. Finally, it's going to cost billions of dollars to address.'' The White House, citing cost and scientific uncertainty, supports further research but no specific action for now on acid rain. Congress has yet to seriously attempt to pass an acid rain cleanup bill.
Toxic waste dumps are another major second-wave issue. Lee Thomas, EPA assistant administrator for solid waste, estimates there are 1,400 to 2,200 dangerous dump sites in the US. In the last five years, EPA has done cleanup work at only 188 sites, Mr. Thomas says. The question now is money for more progress: How much, how fast, and from where?
''Superfund,'' the $1.6 billion federal dump cleanup program, will run out of cash next year. The House has already passed a bill that would pump $10 billion into Superfund by 1990, with most of the money coming from a tax on crude oil and raw chemicals. A Senate committee on Sept. 13 cleared a $7.5 billion Superfund bill. The Reagan administration admits the fund will need much more money, but wants to wait until next year to address the problem.
Dumps, however, aren't the only place you can find toxic chemicals. Controlling toxics that have escaped into water or air through corroding containers, evaporation, and incineration, is yet another problem the US will face in years ahead.
The EPA is moving slowly to corral runaway toxics. So far, the agency has set safety standards only for coke-oven emissions, mercury, asbestos, and a handful of other hazardous air pollutants. Progress on water toxics is even further behind, critics complain. ''Forty-two states have or will soon have air-toxic programs that go far beyond what the federal government requires,'' Mr. Becker says.
Finally, the US must decide what to do about several other vexing water pollution problems: ground-water contamination and runoff from farms, construction sites, and city streets.
Ground water is liquid held in aquifers underground. Pumped up through wells, it provides drinking, cooking, and washing water for almost half the US. It does not flow swiftly, as surface streams do; and thus, once polluted, it stays polluted for a long time.
A Council on Environmental Quality survey found contaminated ground water from Maine to Hawaii, with road salt, septic tanks, fertilizers, and leaking waste dumps the chief culprits.
EPA deputy administrator Alvin Alm said recently that stopping ground-water contamination is the agency's ''No. 1 priority.'' EPA's ground-water action plan , released last month, sets aside $7 million for 1985 to help states prepare ground-water plans.
Runoff (also called ''nonpoint-source pollution'') is a type of pollution that's particularly difficult to capture. How do you keep rain from washing fertilizer off topsoil and into a nearby river? Do you build dikes, or plant hedgerows?
Sierra Club lobbyist Larry Williams estimates that 29 states need runoff control programs. A Clean Water Act revision passed by the House in June would allow $150 million for such efforts over the next four years. A Senate bill is pending.
As the proposed expenditure shows, environmental cleanup isn't cheap.
Between 1972 and 1982, the US spent $626 billion (in today's dollars) for pollution control. That figure represents about 2 percent of the nation's gross national product. Sixty percent of this money was spent by business; most of the rest came from government.
Over the last four years, US environmental spending has actually declined slightly. ''You're not getting old (pollution control) equipment replaced,'' claims William Drayton, a Carter-era EPA assistant administrator. ''You're not getting new equipment put in.''
Most experts predict the US will spend the same percent of GNP on pollution control in the years ahead.
Still, that will amount to billions of dollars on the environment over the next decade. A recent EPA report estimates that between 1981 and 1990 the cost of complying with the Clean Air Act and Clean Water Act will be $526 billion.
In addition, the country will be spending some $12 billion annually on hazardous waste control by 1990, estimates the Congressional Office of Technology Assessment. Other second-wave problems will be equally expensive to solve: Refurbishing urban sewer systems to prevent raw sewage from escaping during storms could cost $35 billion over the next 20 years.
Will all this cash be spent wisely? Is it enough to make the country clean? Is it too much: Will large sums be spent on actions that aren't worth the money?
In the '70s, the EPA was reasonably sure what the risks posed by conventional pollutants were and what needed to be done to control them. When it comes to ''second wave'' environmental problems, many experts say, there's no such certainty.
For one thing, environmental agencies today are being asked to judge and set standards for hundreds of toxic substances widely spread through the environment , instead of a few pollutants from easily found smokestacks or pipes. For another thing, toxics are in many ways still a mystery. Scientists don't really understand how most toxics move in the environment or how they might affect humans.
''We may have to make many more judgments that are not fully informed by science,'' says Reilly.
Given such uncertainty, should the US rush in and spend piles of money cleaning up toxics, to ensure absolute safety? Or should toxic pollutants be left in the environment until their dangers are known and money can be spent more efficiently?
Where you draw the line between these extremes depends on your point of view. The EPA's Ruckelshaus favors deciding what to do through the use of ''risk assessment.'' This is a formal process that uses whatever scientific data there is to balance risks from pollution againt cleanup costs.
''The ultimate goal of this effort is to get the American people to understand the difference between a 'safe' world and a 'zero-risk' world with respect to environmental pollutants,'' Ruckelshaus said in a recent speech.
Some environmentalists, however, say this approach is too stingy. They say that the nation must err on the side of caution, and that cost considerations will lead to environmental regulation that provides less safety than it should.
''The goal is no one ought to lose life or health to these pollutants,'' says David Doniger, senior attorney at the Natural Resources Defense Council. ''In the interim you do the best that you can.''
In the end, say some environmentalists, our goal should not be managing toxic waste, but cutting back its production. Substitutions should be made for hazardous materials, where possible: The paint industry, for instance, has already replaced many dangerous inorganic pigments with organic ones. Recycling should be encouraged.
''The objective ideally is to encourage a second chemical revolution,'' Reilly says. ''As someone has said, a pollutant is a resource out of place.''
Previous articles in this series ran on Sept. 14 and 21. The Domestic Policy Association is a nonprofit, nonpartisan group that encourages discussion of public issues, explores alternatives for solving problems, and aims to identify common ground. Those wishing to participate in this year's forums should write to Dr. Jon Rye Kinghorn, Domestic Policy Association, 5335 Far Hills Avenue, Dayton, Ohio 45429, or call (513) 434-7300 for information.