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Air Pollution Effects from 2001 Wildfires

Smoke from three large wildfires in Placer County this past summer had a severe air quality impact on residents and travelers in numerous communities throughout the Sierra Nevada including the State of Nevada. While air quality is poor at times during the summer months due to increased ground level ozone pollution, dense smoke from wildfires exacerbated the problem for five weeks. High-pressure coupled with hot temperatures lead to air quality so poor, at times, from smoke and ozone (O3 ), air districts officials issued health advisories for sensitive individuals or health alerts for the population as a whole.

The first wildfire, the Gap Fire, in the Blue Canyon area, began on August 12 th and was contained on August 20 th after burning 2462 acres of forestland. Smoke from the dense vegetation burning drifted northwest towards Nevada County and beyond, forcing the closure of Interstate 80 for several days. Air districts in Placer, Nevada, El Dorado Counties and Washoe County, Nevada, monitored the air with various types of equipment and provided timely air quality health advisories/alerts.

Air monitoring equipment located in Grass Valley and Truckee (Nevada County), Auburn, Colfax and Lincoln (Placer County), South Lake Tahoe (El Dorado County), and Washoe County (Nevada) is operated year round. Particulate Matter 10 microns (ug/m3) in size and smaller and ozone (O3 ) are monitored. For most sites, PM-10 data is collected once every six days for a 24-hour period while other sites use equipment that continuously monitors for PM-10 and O3.

PM-10 and O3 pollutants raise concern since breathing polluted air can have both short term and permanent long-term health effects. The smaller particulate matter can get past the protective filters of the throat and lodge deep in the lungs. The PM-10 health based standard for California (CA) is 50 ug/m3 and the federal is 150 ug/m3 . For perspective a hair follicle is 60 microns. Ozone is a strong irritant that can cause airway constriction, forcing the respiratory system to work harder to provide oxygen. The federal health based standard for O3 is 0.12 parts per million.

During the Gap Fire while smoke was dense at times air quality data showed that the measured level of smoke was between 25 ug/m3 to 37 ug/m3 (Grass Valley), below state and federal health standard levels. However, ground level ozone increased and local health officials issued three health advisories and on August 17 th , a health alert was issued when the federal standard was exceeded. On the same day in the Lincoln area (Placer County), PM-10 was measured at 128 ug/m3, well above the CA standard. Although the PM-10 standards were not exceeded in Nevada County, air district officials issued a health advisory for intermittent dense smoke in the area.

As the air cleared from the Gap Fire, a second wildfire, the Ponderosa Fire, started on August 17 th . By the time it was contained on August 23 rd , it had burned 2780 acres. Smoke from the American River Canyon moved into the greater Colfax/Weimar and Nevada County areas. Air quality data collected from both Placer and Nevada Counties showed that there were no instances where the PM-10 standards were exceeded. PM-10 data measured from 7 ug/m3 to 37 ug/m3. The ozone standard was also not exceeded.

With mop up still occurring on the Ponderosa Fire, the third and largest wildfire began on August 25 th . The Star fire started on the Eldorado National Forest and quickly spread onto the Tahoe National Forest. By the time the fire was contained on September 13 th , it had grown to 16,761 acres and smoke affected many Sierra Nevada communities, extending to the Reno/Sparks area. Ash fall out was reported in Truckee, Lake Tahoe and the Reno areas. Satellite imagery showed the smoke plume moving generally east. As the fire grew more widespread, air quality was affected.

Smoke added to the usual seasonal deterioration of air quality and prompted air district officials in the region, including the Washoe County Health Department (Nevada) to issue numerous health advisories. Concerned citizens in Placer County called to find out where they could go to get out of the smoke. Tourists cut back on their outdoor activities in the Lake Tahoe area to minimize their exposure to smoke. School officials kept children inside during recess and lunchtime and many after-school sports programs were canceled in an effort to protect students' health. Air quality officials stated "If you smell smoke, or see smoke around you, consider restricting your outside activities." Additionally, during this time six health advisories and on August 28 th , one health alert was issued when the federal ground level ozone federal standard was exceeded.

Air quality data during the wildfire ranged from good to unhealthy from both smoke and ground level ozone. While air quality varied daily, with little smoke on some days, the greatest health impact occurred on August 29 th . The following table shows the highest readings for each air-monitoring site in the region.

Air Monitoring Location

Highest Reading

CA Standards Exceeded

Federal Standards Exceeded

Auburn (Placer Co.)

112 ug/m 3



Colfax (Placer Co.)

112 ug/m 3



Lincoln (Placer Co.)

60 ug/m 3



Grass Valley (Nevada Co.)

72 ug/m 3



Truckee (Nevada Co.)

66 ug/m 3



South Lake Tahoe (Eldorado Co.)

31 ug/m 3



Cave Rock (Washoe Co., NV)

55 ug/m 3



Reno, (Washoe Co., NV)

88 ug/m 3



South Reno, (Washoe Co., NV)

144 ug/m 3



Incline Village (Washoe Co., NV)

136 ug/m 3



Further review of air quality for the region showed three more exceedances of the CA PM-10 standards. Although there were some days exceeding the CA standards, the dense smoke in the region lead to poor visibility for many days and caused an annoyance/nuisance.

After evaluating the air quality data following each fire, air quality professionals did not find a correlation between the amount of fuel consumed and the daily smoke impacts. On days with lesser smoke impacts, the weather played a role in dispersing smoke, thus reducing its impact. Under the best of conditions, some smoke from a wildfire may affect one's health. However during August and September of this past summer, smoke impacts in the region combined with poor air quality from increased ozone levels affected those living, playing and traveling here. Air district officials provided information to the public to protect themselves, while individuals had the final decision how to protect their health while continuing to go about their daily lives.

This article was originally written for the October/December 2001 edition of California Forests, the newsletter of the California Forestry Association. Author, Ann Mayo Hobbs, has been an air-quality specialist since 1987 and the burn program manager with the Placer County Air Pollution Control District since 1992. Ms. Hobbs has a B.S. degree in Conservation of Natural Resources from the U.C. Berkeley.