Up on the Missoula City-County Health Department’s roof, five air-quality monitoring machines hum away on a cold, clear Dec. 19 morning. There’s no inversion stagnating the valley’s air today, which is especially good news given that new Environmental Protection Agency (EPA) pollution standards governing fine particulate matter went into effect Dec. 18. For the first time in 14 years, Missoula’s air is expected to fall short of the standards, which were stiffened following research suggesting that fine airborne particulate—2.5 micrometers in diameter and smaller, compared to the 60- to 80-micrometer diameter of human hair—has health impacts at lower concentrations than previously thought, says Jan Scher Lainsbury, health department air quality specialist.
“As soon as we became aware of the new standards and looked at our data, we said ‘oh, this is something that needs our attention,’” Lainsbury says.
While Missoula isn’t officially violating the new standards yet, Lainsbury expects that to change. Data from 2004 to 2006 will be used to gauge compliance, and while it can’t be completed until year’s end, preliminary analysis shows Missoula’s air has slightly more fine particulate pollution than new standards permit. While EPA limits for annual pollution—with which Missoula already complies—haven’t changed, the new daily limits were cut nearly in half, from 65 units to 35 units.
Lainsbury expects Missoula’s daily average to end up at about 36 units, due largely to a handful of winter days when air quality is particularly poor.
In November, the health department began studying Missoula’s sources of fine particulate pollution to update and improve upon a decade-old study that found nearly half of fine particulates resulted from transportation, with substantial additional amounts coming from wood burning and industry.
Once that study and the analysis of Missoula data are done, Lainsbury says, the state will likely recommend that EPA declare Missoula a “non-attainment area,” which designation would require Missoula to develop an improvement plan, though it’s too early to say what such a plan might entail.
“This community has made huge strides [toward improving air quality] over the years,” says Lainsbury, “but we have a little more work to do.”