Here on the edge of nation's largest remaining wilderness, the Anchorage winter air is crystal clear. But like so many Alaskan facts startling in their magnitude, this arctic urb has one of the worst air-pollution records in the nation. The city, as well as Fairbanks, farther to the north, ranks consistently among the top-10 United States cities with carbon-monoxide pollution.
On its worst days in the past few years, Anchorage has ranked even above Los Angeles and Denver in its colorless and odorless carbon-monoxide pollution, while exceedingly clean in all other categories of air pollution.
``It's a pollutant people don't recognize, because people don't see it,'' explains George LaMore, air-quality-control officer for the Anchorage Health and Human Services Department.
Thus the importance of this winter's air-pollution alerts -- the first ever called in this city, even though scientists here have routinely documented violations of federal air-pollution standards since the mid-1970s.
Although air pollution levels have for some time reached the air-alert level and above, it was no until this year that the city installed the necessary electronic equipment to call an alert. This equipment obtains pollution readings from several areas simultaneously, allowing an alert to be issued in time to notify the population to reduce their polluting activities, and to warn those sensitive to pollution.
Funding for this equipment was slow to be appropriated, says Mr. LaMore, because carbon monoxide, although a poisonous gas, is not the kind of tangible pollution like the layers of brown L.A. smog, which fuel political crusades.
But as health department officials here explain the situation, it could drag this northern outpost into yet another area of concern much more typical to an urban center in the Lower 48. Further, though automobiles are the main cause of carbon-monoxide pollution, the very environment that makes this city desirable actually is a critical factor in concentrating the pollution.
Anchorage sits in a bowl, surrounded on three sides by mountain ranges. Winter winds here are relatively light, and temperature inversions -- frequent in the winter -- trap cold air near the earth. The air, along with the pollutants in it, remains trapped in the Anchorage bowl.
Adding to the problem, city officials say, is the ``cold start'' phenomenon: Automobiles are in their worst polluting condition when they have been sitting outside in near-zero weather. Their pollution-control systems are designed to work at high temperatures, and as car owners idle the engines to warm them up, much unburned fuel escapes into the air, says Bob Rasmussen, air-quality manager for the city's new vehicle inspection and maintenance program.
Anchorage's two air alerts this year were called when carbon-monoxide levels reached an eight-hour average of at least 15 parts per million (p.p.m.). An air warning is called at an eight-hour average of 30 p.p.m., and an air emergency is reached at 40 p.p.m. A 45-p.p.m. reading, for example, was recorded in 1975.
Half the state's 500,000 population lives in the Anchorage bowl, and there are more vehicles registered here than there are people living here. The temperature and population concentration, combined with a lack of any polluting industries, makes for a pollution situation that can be controlled only by regulation of individual vehicles, Mr. Rasmussen says. The city plans to test all vehicles under 15 years of age to be sure pollution-control devices are working, he says. About 30 percent are expected to fail the test.
Car pooling and bus service are used in the city, but health department officials expect the inspection plan to be the only realistic alternative to the carbon-monoxide problem here. They observe that waiting for a bus in temperatures of minus 30 degrees F. isn't an easy idea to promote among independent Alaskans, who typically have a car and a four-wheel-drive pickup.
``Politically this is all a terribly hot potato. People are screaming at the idea of mandatory auto inspection,'' observes Sue Ann Bowling, an assistant professor of geophysics at the University of Alaska at Fairbanks. It's a similar situation with wood-smoke pollution, she says. In Juneau, wood smoke has reached such a critical stage that Boy Scouts can't burn wood on a campfire. People there have been cited for wood-stove use in their homes, says Dr. Bowling, and when ``you start talking about inspecting people's homes around here [Fairbanks], you're likely to have a revolution on your hands.''
Extremely cold temperatures tend to make the inversion layer more shallow, explains Dr. Bowling. In Anchorage the cold-air layer where pollutants are trapped is typically about 30 vertical feet thick. In contrast Los Angeles's warm-air inversion layer, which traps pollutants, is perhaps 1,200 feet thick, she says. ``So in Fairbanks and Anchorage, 30 feet [of air] is all that we have to dilute [the pollution]. We don't put all that much more per person [in the air] than L.A., but we could still be worse'' in terms of pollution that stays, she explains.