BILLINGS — The replacement of 1,200 wood stoves in Libby with newer, more efficient models has improved air quality, leading to associated health improvements for children in the northwest Montana town, according to a new study.
Airborne particulate pollution in Libby dropped 30 percent over the course of the four-year study. The decline was associated with fewer reports of childhood wheeze, a condition commonly linked to asthma.
Other health conditions showed less or no improvement. But study author and University of Montana epidemiologist Curtis Noonan said the results underscored the potential benefits of upgrading stoves in rural towns where residents have few home heating options.
With no natural gas service in Libby — and plenty of cheap firewood readily available in the surrounding forests — it's unlikely the community is going to move away from wood burning as a major residential heating source, Noonan and others said.
"It's a problem throughout this region of the country and the Northwest and parts of the Northeast," Noonan said. "There are certainly a lot of rural areas like Libby that might have seasonal air quality problems that we just don't have a strong handle on."
Wood smoke is just one pollution problem facing Libby, where hundreds of people have died and an estimated 1,750 have been sickened by asbestos from a nearby vermiculite mine.
A local health official said the stove replacement program could directly benefit asbestos victims by reducing their overall health risks. That includes less air pollution that can aggravate respiratory problems like asbestosis.
"They are already struggling for oxygen," said Kathi Hooper, director of the Health Department in Lincoln County, which includes Libby. "The feedback we've received is that not only is the air visibly cleaner and it smells cleaner and the snow is not turning gray, but people are having an easier time breathing."
The $2 million program to upgrade wood stoves in the Libby area beginning in 2005 was paid for by government sources and donations from the Hearth Patio and Barbecue Association, which represents wood stove manufacturers.
As the air cleaned in Libby, Noonan said there was a drop of about 27 percent in reports of childhood wheeze. That was tracked through surveys of parents, and the decrease was attributed to less smoke pollution in Libby's ambient air.
Results for indoor pollution were mixed. Particulate levels dropped on average by 53 percent in the 21 homes that were monitored, Noonan said. But the change varied greatly, with some homes even showing an increase in particulate pollution concentrations during the four year study.
No health differences were seen between children from homes with wood stoves and children from homes with other types of heating.
School absence reports showed fewer illness-related absences among older students as pollution dropped. Absence rates were higher among students in grades 1 through 4.
Noonan added that Libby offered the "perfect lab" to study wood smoke pollution because the community has both high emissions from wood stoves and frequent cold temperature inversions. Inversions — common in many mountain communities — can trap smoke-filled cold air beneath a warmer layer of air above, preventing pollution from dissipating into the atmosphere.
Wood stoves are used in an estimated 10 million homes across the U.S., according to the federal Environmental Protection Agency. Up to 80 percent of those stoves are older, inefficient conventional stoves.
Several other communities in Montana have been grappling with wood smoke pollution, including Butte-Silver Bow, Lewis and Clark and Missoula counties, said Eric Merchant with the Montana Department of Environmental Quality.
Merchant said the benefits of upgrading wood stoves were demonstrated in Libby, but don't tell the whole story. He said alerts put out by the health department also have helped, including calls to stop burning wood when pollution levels approach levels that could violate federal clean air standards.
"Even if you run the cleanest stoves, if you have a two-week-long inversion they are still going to put out wood smoke," Merchant said.
The Libby study was funded by the Health Effects Institute, a Boston-based organization that examines whether pollution regulations translate into improved air quality. In the case of Libby, the town was out of compliance with national ambient air quality standards when the stove change-out began. It has since come into compliance.
"It sends a clear signal that removing wood stoves could have a measurable improvement in air quality and also in terms of health," said Health Effects Institute vice president Robert O'Keefe.