The Soviets are complaining again about the smog here. They ask, not unreasonably, how anyone can run a marathon during the 1984 Olympics while breathing southern California's brown atmospheric soup.

In a way, such talk is encouraging. The Soviets already wear Levi's and collect Elvis Presley records. When they begin to complain about Los Angeles smog, you know they are almost ready to adopt the American way of life.

Many other U.S. cities have seen their air thicken in this century, but popular mythology insists that Los Angeles be considered the birthplace of air pollution.

Generally arrogant about our sunny weather, those of us who live here have often ignored the problem. Spanish explorer Juan Rodriguez Cabrillo dubbed the area bahia de los fumos (bay of the smokes) more than 400 years ago, when he saw the brownish haze from Indian fires hanging over the coast. But as late as 1943 the Los Angeles Times still seemed perplexed by the byproduct of automobile and factory fumes reacting to sunlight and trapped beneath a curious upper layer of warm air. "City Hunting for Source of Gas Attack," said a Times headline that year.

The recurrent jokes about Los Angeles smog, heard even in Moscow, ignore older pollution pits such as 19th-century London or early 20th-century Pittsburgh (where Los Angeles historian John D. Weaver says the term "smog" originated). They also overlook how much this city's air has changed.

I can remember vividly my first week of college here, upon first arriving in the Los Angeles smog belt. After a set of tennis, my throat felt as if I had swallowed the ball. Natives gave me the usual advice: ignore it. After a month, I had developed a tolerance for ozone and hydrocarbons. After two months, I was enjoying them, like a Fiji Islander invigorated by annual typhoons. I would sit on a bench and watch the yellow-brown mist twist in lovely patterns above my head.

Nineteen years later, I live again not far from that smog belt campus. But the old thrills are gone. Two decades of lead-free gasoline, catalytic converters and smokestack scrubbers (and two years of unusually cool weather) have robbed the air of much of its flavor.

According to Bill Sessa, communications adviser to the State Air Resources Board, carbon monoxide and lead levels have dropped in the last eight years. The familiar haze still visits us, but less often. In 1967 Los Angeles had five third-stage (most serious) smog alerts. Last year we had none.

The Los Angeles Olympic organizing committee, quick to cite these facts, has nonetheless arranged to ease the fears of fresh air enthusiasts from the Soviet Union and elsewhere. Olympic committee spokesman Amy Collis-Quinn said marathon runners next year will stride off in the early morning, before any brown clouds can gather.

Soviet diplomats may still make a fuss about whatever unfamiliar odors hit them as they step off the plane. Myths die hard. But the killer smogs are gone and our brown haze seems likely to fade, if not as quickly as it does elsewhere.

This is nice for those of us with aging lungs, but there is one thing I will always miss: the sunsets. Late afternoon was a romantic time in my freshman year. We would sit and watch the western skies light up with the golds, oranges and pinks filtered by the wonders of 20th-century chemistry. It was better than a Walt Disney movie, a form of modern art they will never be able to appreciate in the Kremlin.