A crude cartoon was waiting for John McGuire of the Environmental Protection Agency when he arrived in St. Clairsville, Ohio, for a public hearing on enforcement of pollution rules. It depicted an EPA official being shot in the head.

"I would rather have seen a 'Welcome' sign," McGuire observed, "but when people are told they're out of work because of environmental regulations, they're going to be upset."

In New York, EPA officials were surprised to find congressmen supporting and newspapers editorializing in favor of relaxing pollution rules for two Consolidated Edison Co. power plants, even before the company had applied for the necessary state permit.

The result has been that a decade after Americans looked around and noticed that some days they couldn't see very clearly, the nation's air is only marginally cleaner than it used to be.

"As a holding action you could say [the Clean Air Act of 1970] has been successful," said David Hawkins, who heads EPA's air pollution control effort as assistant administrator of air, noise and radiation. "There are more cars and more industry, but the problem is not appreciably worse." He agrees, however, that the verdict depends on who is making the judgment.

Of an estimated 20,000 industrial sources that each cough out 100 tons of air pollutants or more every year, 18,000 are in compliance with clean air laws, according to the EPA. But about 800 of the remainder aren't even close, and they tend to be the biggest, dirtiest and smelliest of all: oil refineries, steel plants, paper mills, large power plants.

Now, with a sagging economy and the push to burn coal, the violators can rally support with arguments that the cost of controlling the smokestacks means fewer jobs and delayed conversion from oil.

"It's a continuous fight to get the states and industries to meet the goals we thought would have been met by 1975," said Rep. Henry A. Waxman (D-Calif.), chairman of the House health and environment subcommittee. "We have to convince them that clean air is not inconsistent with energy production."

The big problem companies are also the richest, able to entangle enforcement efforts in lawsuits.

At the end of 1978, Justice Department attorneys were pressing 475 enforcement cases for EPA and defending the agency in 750 suits, according to congressional testimony last May. The suits mainly were from businesses protesting regulations or charging overzealous enforcement, but included many from citizen groups accusing EPA of half-hearted measures. About 110 of the cases involved air pollution.

"Basically, we litigate over what is compliance and what isn't," said McGuire, head of EPA's Chicago regional office. At the Ohio hearing, where he received the threatening cartoon, 1,000 persons made clear that they thought the rules were being enforced sufficiently -- and had cost them jobs.

EPA counters this by meeting with union leaders to explain company finances to them, but agency officials acknowledge this only works some of the time.

In New York, newspaper editorials and politicians last summer were urging that Con Ed be given permission to test-burn a higher sulfur oil even before the company had applied to do so. Critics complained that the pressure, orchestrated by Con Ed, forced New York State to rush through approval in October without much study.

"Any data you rely on from computer projections are always subject to judgment calls and debates," said one EPA official, who asked not to be named. "That's where they get you."

Many companies simply drag their feet, and until recently could snicker at threats of lawsuits. A small but typical case concerned the Beard Construction C., a roadpaving firm near Hartford, Conn., "with a state reputation as one of the compliance problems there," recalled William Drayton Jr., EPA's planning director.

Of the six asphalt-makers in the state, five had complied readily with clean air rules, he said.

"But these guys would promise to put the controls on at the end of their summer work season, and then something would happen and there would be excuses," Drayton said, "and then it would be the new season. . . . Finally, we did take them to court."

The problem was that the original Clean Air Act lacked believable penalties. It allowed criminal fines of $25,000 per day of violation -- more in some states -- but judges proved reluctant to make criminals out of air polluters. They would not impose such fines, especially when there had been years of violations.

"The history was that no one was ever charged much of anything," Drayton said.

The Clean Air Act amendments of 1977 helped some. Now there are civil penalties that equal the amount a violator might have earned on the money it saved by not installing pollution controls. So if a company dallied a year on installing equipment worth $50,000, the fine might be what that $50,000 could have earned at 15 percent interest, or $7,500. The equipment also would have to be put in.

Even so, there have been problems. About 10 suits against utility companies stagnated in 1978 while EPA and Justice Department lawyers argued over whether the new penalty technique could apply to electric companies, where profits are set by government regulation. Other methods now are used in computing penalties.

Some EPA critics charge that most of the agency's travail arises from such intragovernmental bickering and not from industry resistance. Nobody expected the industries to be happy about the rules, but environmental groups cried foul when President Carter's inflation fighters began what looked like an attack on EPA.

The classic case was the Tennessee Valley Authority multimillion-dollar utility settlement last January. After lengthy litigation over whether emissions from TVA's many power plants met clean air standards, a tentative agreement by TVA to correct its problems with EPA was torpedoed by a letter from Carter's chief of the Council on Wage and Price Stability, Barry Bosworth.

He asked EPA whether less inflationary solutions had been researched, and the judge in the case sent the two sides back for further discussion. They are still talking and the power plants are not yet complying with the law.

"EPA never went through a cost analysis for requiring some things and not others," Bosworth explained recently. "Why spend $100,000 to save one life here when you can save a life there for $10? But the TVA is not a profitmaking company; it's a public agency. What does it care?"

His letter, Bosworth said, was only an effort to help clean the air at less cost, but he agreed that few people saw it that way.

"The moment you start to criticize, instead of seeing it's their methods you're after, they think you're critizing their goals," he said.

Everyone, of course, wants clean air and questions only the methods of getting it. How much monitoring should be required on smokestack air pollution scrubbers once they are installed, for example? Congressional staff members recall a technician who kept tabs on the puffs from a smokestack at the Morgantown, Md., power plant by watching a television monitor. "It works just fine -- during the day," he told them.

Broken equipment, erratic dials and deliberate neglect can save a company money. EPA's new "bubble" technique, which will count all pollution sources in one plant together instead of individually, will require sophisticated checking to make sure overall pollution limits are honored. Yet EPA must rely on the polluters themselves to provide most of the figures.

Utilities complain that the regulators don't understand economic reality.

"The EPA is a dedicated group, but it's unbalanced with too many people from the environmental movement," said George Freeman, a Richmond attorney for the Utility Air Regulatory Group that lobbies EPA during rulemaking. The 1977 Clean Air Act amendments were badly written, he added.

Hawkins disagreed, saying: "It's a good law, but it could be improved." After 10 years in the environmental protection field, first as an attorney for the Natural Resources Defense Council and then with EPA, Hawkins is sobered.

"I have had my sights adjusted," he said. "We're dealing with a problem whose solutions are measured in decades."