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Picnic Rock Fire

Firefighters in heavy smoke

Smoke monitoring equipment

Smoke from wildland fire is a large and growing source of air pollution emanating from National Forest system lands. It contains hundreds of chemicals in the form of gases, liquids, and solids. Smoke can pose potential health, visibility, safety, and nuisance problems. Forest managers, fire managers, and air resource specialists must address these issues when and where appropriate to minimize smoke impacts to public health and welfare.

National Forest system lands contain ecosystems substantially departed from natural fire regimes, as well as spectacular scenery that can be impacted by smoke from unplanned and planned fires. Decades of aggressive wildfire suppression and other land use practices have given rise to ecosystems with unnaturally heavy fuel accumulations, proliferation of invasive exotic species, and uncharacteristic wildfires. Large wildfires produce more smoke and air pollution than planned fires (prescribed fires) or naturally ignited fires allowed to burn under pre-planned conditions for ecosystem benefit (wildland fire use fires). Nationally, the restoration of fire-adapted ecosystems to effectively lessen the likelihood of large wildfires is a high priority.

Public and Firefighter Health

The chemicals in smoke that cause the most hazard to human health are carbon monoxide, a group of gases called aldehydes, and tiny particles of solid matter that are small enough to be inhaled. Particulate matter is the main pollutant of concern as carbon monoxide, aldehydes, and the hundreds of other compounds emitted by wildland fires are found in very low concentrations at short distances away from a fire.

Coarse particles about 5 to 10 microns in diameter deposit in the upper respiratory system. Fine particles less than 2.5 microns in diameter can penetrate much deeper into the lungs. These fine particles deposit in the alveoli where the body's defense mechanisms are ineffective in removing them. People with heart or lung disease, children, and the elderly are considered sensitive to exposure to particulate matter. The effects of breathing wildland fire smoke include eye and throat irritation, shortness of breath, headaches, dizziness, and nausea.

Public exposure to smoke is a concern because eighty to ninety percent of wildland fire smoke (by mass) is within the fine particle size class (PM-2.5). Prescribed fire managers need to identify smoke-sensitive areas such as communities, hospitals, non-attainment areas for particulate matter, and highways, and use appropriate mitigation and evaluation techniques to minimize smoke impacts. Weather, climate, and air quality monitoring data can be used to help fire managers modify smoke management techniques as needed. These data can also help local health departments alert citizens about the effects of smoke and where it may travel. For more information on the health effects of smoke and deployment sites and information for satellite enhanced smoke monitoring, visit http://airnow.gov/ and http://www.satguard.com/usfs4. More protective health advisory statements for particles may eventually be developed to reflect the 2006 National Ambient Air Quality Standard for fine particulate matter. Fire managers can monitor the air quality index for particulates during prescribed burning seasons and integrate public information messages about restoration of fire-adapted ecosystems with air quality.

Wildland firefighters are exposed to smoke for various lengths of time. Those on initial attack are closer to the actual fire and breathe in a lot of smoke, but typically for short periods of time. Firefighters on project fires that take days or even months to control usually work further away from the actual fire, but for longer periods of time. Recent studies show that smoke is a greater hazard for firefighters when the wind sends smoke in their direction, when they spend long periods of time putting out smoldering stumps and logs, and when initial attack firefighters have to surround a fire quickly. Extended periods of smoke exposure in base camps may also pose hazards to firefighters. Battery-powered smoke samplers that firefighters can wear are available for fire managers. For more information regarding smoke impacts on firefighters, visit http://www.fs.fed.us/pnw/fera and http://www.treesearch.fs.fed.us/pubs/5388.

Visibility, Safety, and Nuisance

Introduction of particulate matter and certain gases into the atmosphere interferes with the ability of an observer to see landscape features. Fine particulates (PM-2.5) that are prevalent in smoke are more efficient at scattering and absorbing light and impairing visibility than coarse particulates (PM-10). Smoke can cause short-term visibility impacts by obscuring the form, contrast detail, and color of near and distant features. It poses a safety hazard when it obscures visibility on land, water, or aerial transportation routes. Smoke can also cause public nuisance and complaints about loss of visibility, odor, and soiling from ash fall-out at relatively low pollutant concentrations.

For more information on fire emissions, modeling, and monitoring, visit the regional planning organization website in your area (see home page links section), and: