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Denver’s ‘Brown Cloud’ Is Back

February 12, 1993

DENVER (AP) _ Like a horror movie sequel, the Mile High City’s dreaded ″brown cloud″ is back.

The air pollution, which often smells like a stockyard, has blanketed metropolitan Denver more often this winter than in the six previous years.

On a single day in January, the worst air pollution in five years hung over the city, obscuring the lower levels of buildings and the Rocky Mountain foothills, said Laura Bishard, administrative officer of Clean Air Colorado.

The main culprit isn’t vehicle exhaust or fireplace emissions - it’s the weather, particularly inversion layers that trap pollutants, she said. Inversion occurs when warm air forms a cap above cool, stable air.

Ken Lloyd, executive director of the Regional Air Quality Council, said an inversion effect is like ″putting a lid on a box and pumping all this pollution into the box.″

Denver has been fighting air pollution problems for more than two decades, and was on the cutting edge nationally with its mandatory oxygenated fuel program, which went into effect about six years ago.

In recent years, the city has concentrated on meeting federal standards for carbon monoxide and fine particulates, and a state standard for visibility, Bishard said.

Carbon monoxide, an invisible gas that can cause lung and heart problems, is created by internal combustion engines, which pose special problems at Denver’s mile-high altitude where fuels burn incompletely.

Fine particulates are comprised of sand put on icy streets that vehicles grind into tiny fragments, some woodburning emissions, fireplace soot and agricultural dust.

Since December, the city has topped federal standards five times for carbon monoxide and four times for fine particulates, Lloyd said. By comparison, the city violated the fine particulate standard once in the previous six years and the carbon monoxide standard an average of five times in the past three years.

″We have the exact same programs in place that we had last year,″ Bishard said, blaming weather conditions for the sudden change.

Dr. Lee Newman, a lung specialist at National Jewish Hospital in Denver, said the bad air has taken a toll on respiratory patients.

″This has been an unusual year in terms of the number of people we’re seeing who are experiencing more aggravation,″ he said, adding that asthma and emphysema patients have been particularly hard-hit.

A winter program to fight air pollution was established in metropolitan Denver in 1986. It sets up procedures for implementing mandatory woodburning bans and voluntary restrictions for driving on days when pollution is too high.

In addition, most motorists in nine counties are required to use oxygenated fuels from Nov. 1 to April 30.

With a forecast of an increase in vehicle miles from today’s estimate of 37 million miles a day to 70 million miles a day by 2010, air pollution control officials are developing new proposals.

One plan is to improve vehicle inspection and maintenance. Denver officials also are implementing plans this month to intensify the street-sweeping program and to cut street sanding by 30 percent.

But the public also has a role, Bishard said.

″We need to come to terms with the fact that the auto is the heaviest contributor to our air pollution program. Without a mandatory program, the best we can do is voluntary and when you have a voluntary program in effect, it’s up to people to participate,″ she said.

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