Health Hazards of Smoke Spring 2001
Fire Storm 2000
The 2000 fire season ranked as one of the worst in the past 50 years. With thousands of fires and over 7 million acres burned, the season strained human and physical resources to the limit. Army, Marine, and National Guard units, as well as firefighting personnel from Canada, Mexico, Australia, and New Zealand assisted firefighters. With the fires came a pall of smoke that blanketed large areas of the Mountain West. While the smoke from the 1988 Yellowstone fires may have been more concentrated, it was isolated and didn't last as long. The smoke from the year 2000 fires in Montana and Idaho accumulated in mountain valleys, affecting the lives and health of thousands of residents.
Satellite view of Western Montana during
a typical day in August 2000.
Air quality is determined by measuring the amount of small particles in the air. Particles smaller than 10 microns affect air quality, visibility, and health. Montana and Idaho annually average 19 to 24 µg/m3 (micrograms of particulate per cubic meter of air), well below the U.S. Environmental Protection Agency (EPA) PM10 standard of 50 µg/m3. During August 2000, smoke covered large portions of Montana and Idaho. In Missoula, MT, where the City/County Health Department regularly monitors air quality, 1-hour PM10 levels peaked at 550 µg/m3. Twenty-four hour PM10 levels frequently averaged above 100 µg/m3 and several exceeded 200 µg/m3.
Air pollution alerts were common. The EPA 24-hour air quality standard is 150 µg/m3 (Missoula calls a stage 1 alert when the PM10 exceeds 80 µg/m3). Missoula calls stage 3 alerts when the 24-hour levels approach 300 µg/m3. Because much of the smoke was coming from the Bitterroot Valley south of Missoula, smoke levels in the valley were usually higher than those recorded in Missoula (figure 1).
Figure 1—Hourly PM10 comparison between Stevensville
and Missoula, August 9, 2000. From: Missoula City/County
Department of Environmental Health.
In the Bitterroot Valley, 8-hour averages were higher than 300 µg/m³ five times and one 1-hour concentration approached 1,000 µg/m3. A monitor at the Valley Complex fire camp in the southern part of the Bitterroot Valley recorded some 24-hour PM10concentrations greater than 100 µg/m3. At times the smoke was deep enough to cover the peaks of the Bitterroot Mountains, which rise 6,000 feet above the valley floor.
Salmon, ID, south of the Bitterroot Valley, experienced high levels of smoke exposure from the extensive fires in the area. According to the Idaho Department of Environmental Quality, 24-hour PM10 levels measured near the local school in late August exceeded 200 µg/m3 on several occasions. Hourly levels of particulate smaller than 2.5 µm (PM2.5) exceeded 175 µg/m3 on one occasion with several readings over 100 µg/m3. Hourly PM2.5 levels inside the school exceeded 100 µg/m3 for 1 hour with several readings over 50 µg/m3.
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