Every morning as he pilots his 1966 Volkswagen to work here, Jim Chandler must leave his suburban mountain home and head down into what he refers to with a wince as "that awful brown cloud."

"When I moved here 12 years ago and was a lineman for a power company, you could climb a pole in the morning and see every building in the city sparkling in the sun," Chandler said. "Now all I see in the morning is a polluted cloud."

Denver, which once boasted air so clean that doctors around the country sent their asthmatic patients here for releif, now what one senior state official describled recently as "a poison cloud" hanging overhead.

During the fall and winter months, when the pollution is most severe, Denver is neck-and-neck with Los Angeles as the American city most poluted with carbon monoxide, nitrogen oxides, hydorcarbons and particulate matter. If Denver had Los Angeles's humidity, the Colorado official said, its pollution would be twice as bad.

Chandler, who left his lineman's job some time ago to become a physician, now heads the department of emergency medicine at the University of Colorado Medical Center here. This past winter he and two colleagues made a disturbing discovery.

The three began keeping tabs on the relationship between the patients coming into their emergency room - the city's third busiest - and the air-pollution level. During a 92-day period they discovered an apparent correlation between people complaining of chest pains and shortness of breath and peaks in the city's carbon monoxide-levels.

They reported their findings to the American Association for the Advancement of Science at the group's February meeting here and are planning an expanded study on the relationship. "Our numbers indicate a trend," said Chandler, "and it's enough to make us concerned."

To experts who have studied ths problem, Denver's brown cloud - a reference that nearly everyone here immediatley understands - is no surprise. Similar polluted clouds have been forming in recent years over unexpected places such as Vail and Aspen, Colo., Albuquerque Las Vegas and Phoenix.

"These were the places you need to head for to get away from that sort of thing," said Frank Covington, director of the Environmental Protection Agency's Air and Hazardous Material Section in San Francisco. "Now they're finding clean air is becoming a rather scarce commodity wherever vehicular traffic has sharply increased."

The 1.2 million people who live in Denver and its suburbs have a love affair with the automobile that surpresses even that of Los Angeles residents. Denver's nearly 1 million cars and trucks make it the heaviest vehicle - using city in the nation for its size and the city with the lowest number of riders per vehicle.

"We know where the problem lies," said Joseph Palumba, technical secretary for the Colorado Air Pollution Control Board. "The only improvements in our air are going to follow improvements in our air are going to follow improvements inauto emissions."

To some extent that may be happening. EPA officials said federal emission restrictions have cut auto pollution 80 per cent below 1970 levels. Full federal standards, scheduled to be enforced by 1978, appear likely to be pushed back under President Carter's energy program. But Colorado and other states where auto pollution is bad are moving slowly to enact their own emission standards. California is the only state with such standards now in effect.

Observers here believe the Colorado liegislature, which has voted down a state emission-control standard on two occasions, will pass a watered-down version this year.

But even with a new law, Colorado Air Pollution Control Board members predict that only mandatory gas rationing or radical engine redesign to lower emissions could cut vehicle pollution to acceptable levels.

According to federal clean air experts, the West is particularly vulterable to auto pollution because of its sprawling cities and lack of mass transit, causing a dependence on the automobile that is likely to get worse, particularly in the so-called Sun Bolt, where growth projections are the heaviest. One auto industry study last year showed that eight of the nine cities with the highest [WORD ILLEGIBLE] are in the Sun Belt.

The same areas also are undergoing some of the worst vehicle-produced increases in smog In the Denver the situation has reached the point where the brown cloud often bloocks out the city's spectacular Rocky Mountain backdrop. The legislature is deciding whethre to spend $100,000 to renew smog-damaged gold leaf on the capitol dome and state maintenance officials complain of a never-ending war aginst a brown tinge that discolors the marble on state buildings.

"I've never experienced Los Angeles smog," said Dick Dillon, who flies a traffic helicopter for radio station KIMN here, "but this stuff, is browner and just looks dirtier."

One problems is the city's altitude - 5,280 feet. Studies have shown that Denver has 17 per cent less oxygen in its air than is found at sea level. The low oxygen level causes poor engine combustion and leads to excessive pollution. Carbon monoxide emissions post the most serious problems, according to Dr. John C. Cobb, a university medical center researcher.

In a report delivered to the AAAS in February, Cobb noted that a nation-wide test of blood samples taken in various cities showed carbon monixide levels in the blood were highest in Denver. Other researchers have discovered that Denver's heart-attack death-goes up significantly on days when carbon monoxide levels are high.

Vehicle air pollution also has caused an ozone problem. The sun, which is more intense in the "Mile High City" than it is at sea level, converts more hydrocarbons and nitrogen oxides of the pollution into the colorless, odorless and tasteless gas than it does in other cities. Ozone aggravates attacks of such respiratory diseases as asthma. Ironically, the National Asthma Center was built here because of Denver's altitude and dry climate.

"People used to come out here for their health," said Denver EPA official Charles Stevens. "Now they go somewhere else because it just isn't healthy hereanymore."