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Health Impacts


Smoke rising from a wildfire

Smoke rising from a wildfire. Photo courtesy of Andrea Holland-Sears.

The chemicals in smoke that cause the most hazard to human health are carbon monoxide, aldehydes, and tiny particles of solid matter that are small enough to be inhaled. Particulate matter is the main pollutant of concern to the public 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.

How Smoke Affects Your Health

Particulate matter is the principal pollutant of public health concern related to wildland fire smoke. Coarse particles about 5 to 10 microns in diameter (PM10) can deposit in the upper respiratory system. Fine particles less than 2.5 microns in diameter (PM 2.5) can penetrate much deeper into the lungs. Typically wildland fire events result in relatively short-term smoke exposures (hours or days). With precautions that reduce smoke exposure such as limiting outside exertion during smoke events, healthy individuals may not suffer serious long-term effects although temporary minor irritation may result when particulate matter concentrations are elevated. The effects of breathing wildland fire smoke include eye and throat irritation, shortness of breath, headaches, dizziness, and nausea.

Those who are most sensitive to exposure to particulate matter include people with heart or lung disease, children, and the elderly. For sensitive individuals smoke can aggravate lung disease leading to asthma attacks or acute bronchitis and can also increase the susceptibility to respiratory and cardiovascular illness. For more information on health effects of particulates read the EPA Partical Pollution and Your Health guide.

Wildland Firefighters and Smoke

Firefighters attacking a brush fire in Southern California

Firefighters attacking a brush fire in Southern California. Firefighter smoke exposure is a health concern. Photo courtesy of Nathan Judy.

Wildland firefighters are at risk for health concerns that include prolonged smoke inhalation. Research studies indicate that smoke exposure reaches its highest levels among firefighters maintaining fire within designated firelines and performing direct attack of spot fires that cross firelines. For these firefighters peak exposure situations can be several times greater than recommended occupational exposure limits for short-term exposures. Winds carrying smoke into firefighters’ breathing zone can exacerbate the impacts.

Extended periods of smoke exposure in base camps may also pose hazards to firefighters. Firefighters can use electronic carbon monoxide (CO) monitors to track and prevent overexposure to smoke. For more information, visit the USFS Fire and Environmental Research Teams "Effects of Smoke Exposure on Firefighters Health".


High concentrations of ozone can cause inflammation and irritation of the respiratory tract, particularly during physical activity and can aggravate asthma attacks. The resulting symptoms may include pain when taking a deep breath, coughing, throat irritation, and breathing difficulties. Exposure to ozone can damage lung tissue and increase the susceptibility of the lungs to infections, allergens, and other air pollutants. Medical studies have shown that health problems caused by ozone may continue long after exposure.

In some National Forests, particularly in the Southeast, Northeast and California, ozone concentrations have exceeded standards set by EPA to protect human health. While the Pacific Northwest and Intermountain West typically experience lower levels of ozone concentrations than other regions of the country, levels are increasing in the Colorado Plateau and Rocky Mountains regions and sometimes exceed the national standards. Learn more about the health effects of ozone.

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