SALT LAKE CITY (AP) -- Particulate pollution in Logan on Thursday was the worst environmental officials have recorded in the nation on an ordinary day in the seven years it has been measured.
Richard R. Long, director of air and radiation programs for the Environmental Protection Agency's regional office in Denver, said the only PM 2.5 readings higher than Logan's came from severe wildfires in Montana.
"It's shocking. ... Particulate matter is the one (pollutant) that kills people," he said.
The Bear River Health Department and the state Air Quality Division issued advisories that the air quality in Logan, a city of 43,000 about 70 miles north of Salt Lake City, was classified as "very unhealthy."
The air quality in Utah, Davis and Salt Lake counties, also suffering under inversions, was classified as "unhealthful," one level better than Logan's.
"Sensitive people with heart or lung disease, older adults, and children should remain indoors and keep activity levels low," according to the advisory for Cache County. "Everyone else should avoid all physical activity outdoors."
The current inversion in Logan is the first time air in Utah has ever been deemed "very unhealthy," said Grant Koford, environmental health director for the Bear River Health Department, which serves Logan and the Cache Valley. "These levels are incredibly high -- higher than we ever thought they would go."
Thursday was the eighth consecutive day of "red" mandatory bans on burning coal and wood in northern Utah.
Since Jan. 8, high atmospheric pressure has held down the cold, polluted air in valleys under a thick layer of warm air. Meanwhile, the ski resorts and mountain communities like Park City enjoy sunny skies and higher temperatures.
Forecasters do not see a possible break for the valleys until at least Monday, when there will be a 20 percent chance of snow.
Until then, the PM 2.5 count is expected to grow. At 65 micrograms of PM 2.5 per cubic meter of air, officials impose burning restrictions and urge everyone to avoid exertion outdoors.
Air monitors began to measure those levels in Logan on Monday and in Salt Lake City on Tuesday. The Utah County level has been hovering just below the "red" zone since Saturday, and Ogden has stayed at or below the "yellow" voluntary burn level since Jan. 8.
Logan's level reached 182 on Thursday afternoon. The closest reading the EPA has seen since PM 2.5 measures were implemented nationally for an ordinary day was in Fresno, Calif., on New Year's Day 2000, when it reached 160.
One reason the pollution is worse in the Cache Valley than in the more populated areas like Salt Lake and Utah valleys is that it is in basin and does not get the small amount of fresh air that Salt Lake City and Provo get off nearby lakes.
It also is colder in Cache Valley, resulting in worse incomplete fuel combustion when vehicles start up.
Cattle and other farm animals in the rural Cache Valley produce ammonia in urine and manure that helps concentrate small particles.
Logan Mayor Doug Thompson, who has asthma, said, "We can't do anything about it. We can't stop living our lives."
However, Koford said people can do something.
Beside leaving their wood stoves off, people can avoid driving and consolidate their trips whenever possible, he said.
(Copyright 2004 by The Associated Press. All Rights Reserved.)