And where the principal, as a safety measure, might soon ask everyone to run in the halls - and not outside. Wintertime air pollution occasionally upends life at Greenville Elementary School.

"It's horrible," said Principal Joel L. Allred, recalling the 20 indoor-recess days in the 2004-05 school year. "It was truly horrible. It was hard on the students. It was hard on the teachers."

Today, the federal government institutes tough new air pollution standards, and while possible sanctions won't be in place for years, Logan already is having to cope with air that reaches unhealthy levels for students at Greenville Elementary and other residents.

State air regulators say it's almost certain that Logan will join about 11 other communities in violating the new regulations for fine-particle pollution. Running afoul of the limits could eventually mean restrictions on transportation funding and businesses. "I'm not sure the standards are as important as the effect on health," says Ed Redd, medical director of the Bear River Health Department. "That's the overriding, long-term goal here." Called PM 2.5, short for particulate matter 2.5 microns or smaller, the microscopic particles are emitted from cars, trucks, industry and coal-fired electric plants. During temperature inversions in northern Utah's valleys, the particles stew in the icy wintertime air with gas fumes and other noxious chemicals and produce pollution that has been proven to harm health.

PM 2.5 particles are so small, they evade the body's natural defenses, such as sneezing and coughing. They bury deep in the lungs, causing heart and lung problems, particularly in the young, the old and vigorous exercisers.

Under the U.S. Environmental Protection Agency's former standard, which all of Utah meets, a violation occurs when daily high-pollution readings over three years are 65 micrograms of PM 2.5 per cubic meter of air or above. Under the new standards, 35 micrograms is the limit, and urban areas of northern Utah from Logan through Juab County will violate that limit, based on readings from 2003-5.

The EPA says the tougher control would prevent 17,000 premature deaths nationwide each year and "yield additional health benefits" of between $9 billion and $75 billion per year.

Of 17 monitors in this region, air quality at a dozen exceeded the new standard over the past three years.

Today's effective date for the new PM 2.5 standard, and a few other changes to the federal fine-particle law, already have started legal wrangling that probably will last for years. One reason is that, even though the new standard is tougher than the old one, some key groups insist the new standard does not go far enough. The EPA's own science advisory panel pressed for a lower standard. So did environmentalists and health groups, including the American Lung Association.

Alice McKeown, air analyst for the Sierra Club in Washington, says scientists have shown in thousands of studies that PM 2.5 is dangerous. Her group was one of many that pushed for a lower standard of 25 micrograms of PM 2.5 per cubic meter of air.

"We're happy that a step is being taken," she says, "but we think it should have been a much bigger step to make sure the air is safe for everyone."

Cheryl Heying, planning manager for Utah's air-quality office, says she won't be surprised to see the regulations tangled up in court, given the fights prompted by the first PM 2.5 regulation, announced nearly a decade ago but still more than a year away from actually being implemented.

"This is going to be a tough standard," she says, "a really tough standard."

Utah's plans for reducing PM 2.5 are not due at the EPA for seven years. With the easy pollution-reducing fixes already in use, no one is sure what the state will have to do to bring PM 2.5 under the limits that begin today.

Meanwhile, the state is looking at grants for retrofitting its diesel vehicles and school buses with updated technology.

Then, there's Logan, Utah's hot spot for PM 2.5. In 2004 it had some of the highest readings ever measured in the nation.

The local health department has rallied citizens to limit the use of wood- and coal-burning stoves, businesses to close drive-up windows on bad air days and everyone to share rides, use mass transit and minimize driving on bad high-pollution winter days.

The Greenville Elementary community is committed to tackling the problem, too.

The parents of half the school's 500 students volunteered their children for breathing tests every school day for two months this winter. Utah State University students will test students before and after midday recess to measure the pollution's impact. USU researchers plan to continue to monitor air quality both inside and outside the school.

Allred is prepared to make the call each day on whether to bring recess indoors. On the bad air days, he'll crowd hundreds of energy-stoked students in the gym.

Given how stressful those gym days have been in the past, he wonders if it might even be safer to have them run off steam in the halls during recess. Parents, he says, want to be sure their children are safe and secure - even if it is from breathing the air outside.

"They are concerned. They want their kids to be protected."

fahys@sltrib.com

Inversion effect

Geography plays an important - and confounding - role in Utah's pollution problem. Because of the mountains surrounding much of northern Utah's populated areas, warm, upper layers of air trap cold, polluted air below. The pollution can build for weeks at a time, until low pressure, wind, rain or snow comes along to scrub the pollution out of the valleys.