Ten years of measures have kept the Treasure Valley’s air quality under federal limits.

Experts say a change in the weather or a return to rapid growth could bring federal sanctions that would limit highway construction or new business development. But so far unprecedented actions taken by the state and local communities have kept the Valley in control of its own destiny.

The Obama administration’s stricter standard for soot, announced earlier this month, probably won’t require new actions to keep the Treasure Valley under the limits.

Smoke from wildfires last summer could push the area over the new annual standard. The U.S. Environmental Protection Agency figures “exceptional events” such as lightning-caused fires into its calculations, however, and that likely will keep the Treasure Valley in what the EPA calls “attainment,” or meeting the federal air standards, said Bruce Louks, Idaho Department of Environmental Quality air quality monitoring manager.

“So far what we’re doing is working,” said Louks.

The new soot standard is set at 12 micrograms per cubic meter of air, down from 15, calculated over three years. The Treasure Valley soot levels averaged 7.4 micrograms per meter from 2009 through 2011.

Soot is known formally as pm 2.5, which stands for particles 2.5 microns or smaller. Those microscopic particles are breathed most deeply into people’s lungs and can lead to heart attacks, strokes and asthma attacks.

A human hair is about 70 microns in diameter.

THREE POLLUTANTS DOMINATE

These pollutants have driven the local effort to control air pollution going back into the 1980s.

- Soot: Woodstoves accounted for much of the particle pollution until local and state officials put in place rules that reduced emissions, especially during inversions that trapped air in the winter.

The Valley barely missed exceeding the three-year standard in 2007 for the pollutants, which come directly from sources such as automobiles and burning wood. Since then, soot levels have dropped, due in part to fewer inversions and fewer miles driven during the recession.

- Carbon monoxide: From 1978 to 2003, the Valley was pushed into nonattainment for the odorless, colorless gas produced by burning fossil fuels. It interferes with the ability of blood to carry oxygen to organs and tissue, slowing reflexes, causing confusion and reducing the ability to learn.

Federal tailpipe emission limits required all cars to reduce carbon monoxide beginning in the mid-1970s. As older cars disappeared, the carbon monoxide problem in the Treasure Valley dissipated.

- Ozone: Just as soon as that problem disappeared, a tougher, more complex problem arose. Ozone is a form of oxygen that can aggravate existing respiratory and cardiac conditions and cause permanent damage to the lungs.

Ozone forms when nitrogen oxide, emitted primarily from cars, mixes with volatile organic chemicals in the atmosphere and is “cooked” by sunlight. The chemicals come from a wide variety of sources, fumes from gas stations and tank farms.

STATE STEPS IN

In 2008, the Treasure Valley barely avoided exceeding the federal ozone standards. The Idaho Legislature and Gov. Butch Otter approved a law that required auto testing in Ada — which already required tests in all but Kuna — and Canyon counties.

“The majority of people recognized that something needed to happen,” said Toni Hardesty, then Idaho Department of Environmental Quality Director and now executive director of the Idaho Nature Conservancy.

After a long fight, Canyon County joined Ada in 2010 in an auto-testing program that forced the worst-polluting cars to be cleaned up. It made the Treasure Valley the only region in the country to implement auto testing without federal requirements.

Since then, the Treasure Valley has stayed below the federal eight-hour ozone standard. The Obama administration delayed lowering the limit in 2011. DEQ’s Louks expect the tougher standards to come back soon, which again would place the Valley close to exceeding the federal standard.

If that happens, it could mean restrictions for industry, small business and road-builders that would last at least 20 years. DEQ would have to write an air quality management plan for getting back into attainment.

If the state’s plan is rejected by the EPA, or environmentalists win a challenge in court as they did in 1999 here, EPA would have veto power over federally funded road and transportation projects.

MASS TRANSIT COULD BE NEEDED EVENTUALLY

In the long run, vehicle testing and other steps that have worked won’t be enough, according to models by Community Planning Association of Southwest Idaho, the regional organization known as COMPASS.

Growth will overwhelm the benefits of testing and having cleaner automobiles unless people get out of their cars, said Matt Stoll, COMPASS executive director. That means communities will need better mass transit systems.

Lack of money stands in the way, Stoll said. The Idaho Legislature has been unwilling to approve local option taxing authority.

“Regardless of ozone, mass transit is needed for the Valley as we continue to grow and gas prices go up,” Stoll said.

Rocky Barker: 377-6484