Even though it has been tied in knots over the budget, Congress agreed this week on a new Clean Air Bill that seeks to reduce much of the nation's air pollution over the next 15 years. While the goal is admirable, people should understand that there is a significant cost - acknowledged loss of jobs, slower economic growth in some cities and greater business expense.

The tough new Clean Air Act is the first updating of federal pollution laws in 13 years.Cleaner air will cost the economy an estimated $11 billion a year in 1993 and anywhere from $22 billion to $50 billion a year by 2005, depending on whose figures are used. Private business says the cost will be high and they are probably right. Congress traditionally tends to underestimate expenses as it justifies federal programs.

In the end, the cost will be paid by fewer jobs and higher prices to consumers for certain products.

Certainly, the goals are laudable. But this is not an easy undertaking. Every corner of life is going to feel the pinch and the deadlines are tight. For example:

- The bill requires a 15 percent cut in smog-causing pollution within six years and 3 percent annually after that until air quality standards are met. Cities have five to 15 years, depending on severity of problem, to meet federal standards.

- Factories must install "maximum achievable control technology" to reduce 189 different toxic chemicals and cut emissions by 90 percent by the end of the decade. This is not just big industrial plants; thousands of neighborhood businesses such as dry cleaners, gas stations and paint refinishers will be affected as well.

- Auto tailpipe emissions must be reduced 30 to 60 percent by 1998. Alternative fuels must be phased in for fleet vehicles. Some 300,000 private alternative fuel cars will be introduced in California.

- The oil industry must provide cleaner blends of gasoline in cities with the worst pollution problems.

- Use of chlorofluorocarbons in spray cans and mechanical equipment must be phased out by 2000 to protect the earth's ozone layer.

- Coal-fired electric power plants must reduce sulfur dioxide emissions by a total of 10 million tons a year by the year 2001 to reduce acid rain. This will particularly affect such plants in the Midwest and could also open up new markets for Utah low-sulfur coal, although this is a touchy issue in areas where high-sulfur coal is mined.

All in all, the measure is perhaps the toughest anti-pollution legislation anywhere. But even its advocates admit it will be costly. Let's hope it will be effective and worthwhile at the same time. Cleaner air at the expense of a choked and stifled economy would be too big a price to pay.