Air Pollution and Public Health in Utah
Wood Smoke and Your Health
What is Wood Smoke? | Health Effects | What You Can Do | Sources of Wood Smoke
In recent decades, the rising cost of fossil fuels, the desire to use renewable energy sources, and the availability of new technologies has led to increases in the use of wood in North America. In developing nations, wood and other biomass fuels can be the major energy source used for household heating and cooking (Naeher et al., 2007).
Although wood is a natural product and has been used as a fuel for millennia, burning wood releases smoke that can impact your health, the health of those around you, and contribute to local air pollution.
Wood smoke is a complex and variable mixture of gases, chemicals, and solid particles (EPA 2013n; Naeher et al., 2007). These include:
- Particulate matter (PM)
- PM2.5: Particles with a diameter smaller than 2.5 micrometers (µm, or microns)
- PM10: Particles with a diameter between 2.5 µm and 10 µm
- Carbon monoxide
- Nitrogen oxides
- Sulfur oxides
- Volatile organic compounds (VOCs)
- Respiratory irritants
- Compounds that can cause cancer (phenols, cresols, acrolein, benzene, formaldehyde, polycyclic aromatic hydrocarbons [PAHs], etc.)
The exact composition of wood smoke can change, sometimes rapidly, based a variety of factors (Naeher et al., 2007):
- Time
- Type of wood being burned
- Moisture content of the wood
- Type of stove or fireplace
- Temperature of the fire and outside air
- Exposure of the smoke to sunlight
Older or poorly maintained wood stoves may not completely burn the wood, increasing the amount of smoke (and thus pollutants) released. Some newer wood stoves use either a catalytic chamber or an insulated secondary combustion chamber to reduce pollution by more completely burning exhaust vapors. Pellet stoves use pellets of compressed wood or other biomass material for fuel. They are typically more efficient and release less pollution than conventional wood stoves (EPA, 1994; EPA, 1996). However, if operated incorrectly, even the most modern wood stoves and fireplaces can produce higher amounts of smoke.
For more information on different wood stove types, visit the EPA's Burn Wise Program
Smoke from a prescribed burn obscures the mountains east of Mount Timpanogos in October of 2014
Health Effects of Wood Smoke | Top
Particulate Matter
PM2.5 is typically the wood smoke component of primary concern, although smoke contains a large number of compounds that can be harmful to your health (Naeher et al., 2007; Washington, 2012). In general, the size of the particles is directly linked to their potential for causing health problems.
- Smaller particles like PM2.5 are most dangerous as they can easily get deep into the lungs (EPA, 2013i).
- They can enter the circulatory system or remain embedded for long periods.
Stagnant air conditions during the temperature inversions common in the winter along the Wasatch Front can concentrate wood smoke and other air pollutants close to ground, increasing the likelihood of health problems.
Populations sensitive to particulate matter air pollution (EPA, 2013i; UDOH, 2014a)
- People with preexisting heart conditions, including:
- Heart failure
- Coronary artery disease (also called coronary heart disease or ischemic heart disease)
- People with preexisting lung conditions, including:
- Older adults, who may have undiagnosed heart or lung conditions
- Children, whose hearts and lungs are still developing
Symptoms of PM exposure
- Irritated eyes, nose, and throat
- Coughing
- A feeling of tightness in the chest
- Shortness of breath
- Fatigue
- Decreased ability to breathe deeply or vigorously
- Increased susceptibility to respiratory infections
- Aggravation of existing conditions like asthma and chronic bronchitis
- Increased risks of chest pain, irregular heartbeat, and heart attacks, particularly in people with pre-existing heart disease
For more information on particulate matter
Carbon Monoxide
Carbon monoxide is a colorless, odorless, and tasteless gas found in both indoor and outdoor air. It is formed when carbon-based fuel, including wood, is not burned completely (ATSDR, 2012b). A poorly vented and maintained wood stove or fireplace can allow dangerous levels of carbon monoxide to build up in the home. Installing and maintaining at least one carbon monoxide detector in your home can prevent and alert you if this occurs.
Populations sensitive to carbon monoxide(ATSDR, 2012b)
- People with preexisting heart conditions, including:
- Heart failure
- Coronary artery disease (also called coronary heart disease or ischemic heart disease)
- People with preexisting lung conditions, including:
- Older adults, who may have undiagnosed heart or lung conditions
- Children, whose hearts and lungs are still developing
People may be more vulnerable to carbon monoxide during physical exertion when more oxygen is needed.
Symptoms of carbon monoxide exposure
- Headache
- Nausea
- Vomiting
- Dizziness
- Blurred vision
- Confusion
- Difficulty breathing
When you breathe air with carbon monoxide, it rapidly enters all parts of the body, including the blood, brain, heart, and muscles. At high levels, exposure to carbon monoxide can be fatal.
During pregnancy, breathing high levels of CO can cause miscarriage and other adverse birth outcomes. Breathing lower levels may harm the mental development of the child (ATSDR, 2012a; EPA, 2013m).
For more information on carbon monoxide
Health Effects Research
The majority of human studies on the effects of wood smoke have been on wildland firefighters and people in developing countries who use wood for cooking and eating (Naeher et al., 2007); both groups typically have wood smoke exposures that are many times higher than those for most people in developed nations, including Utahns. Additionally, it can be difficult to distinguish the risks due to wood smoke from the risks due to other sources of particle pollution. Nevertheless, the majority of the evidence indicates that wood smoke can be hazardous to human health (EPA, 1994; EPA, 2007; EPA, 2013n; Health Canada, 2014; Naeher et al., 2007; Washington, 2012; Zelikoff et al., 2002). Furthermore, particles from wood smoke appear to cause the same type and severity of health problems as other types of particulate matter; there is little evidence that it should be treated separately from other sources of the same type of pollution (Naeher et al, 2007).
Some studies have shown only limited associations between exposure to wood smoke and health problems. A recent study examined the link between the use of wood stoves and fireplaces and breast cancer in Long Island, NY. While women who burned synthetic logs (which may also contain wood) had a higher rate of breast cancer, burning just wood showed no link (White et al., 2014). In a different study, wood stove use during the first year of life was associated with total days of cough among infants in Connecticut and Virginia; fireplace use was not associated with any respiratory symptom. However, both wood stove and fireplace use was intermittent during the study period (Triche et al., 2002).
What You Can Do | Top
Reduce your exposure
- Use the Air Quality Index to monitor the particulate matter levels in your area.
- When PM levels are high, reduce the amount of time spent on high exertion activities, or substitute a less strenuous activity (e.g., taking a walk instead of jogging).
- Plan outdoor activities for days with lower PM levels and spend less time near areas likely to have higher PM levels, such as near busy roads.
- Keep your indoor PM levels low by not using particle sources like wood stoves and fireplaces on bad air days.
- Install and maintain a carbon monoxide detector in your home if you use a wood stove or fireplace. It can alert you before dangerous levels accumulate. Remember that most smoke detectors do not sense carbon monoxide!
Reduce wood smoke
- Follow the Air Quality Action Forecast. On potential bad air days with voluntary or mandatory action alerts, reduce or avoid burning wood and other solid fuels.
- Burn only dry wood that has been well seasoned (under 20% moisture is best). Dry wood burns hotter with less smoke.
- Keep your fire hot and don't add too much wood. Dampering down a wood stove or adding too much wood cuts off the air, which creates more smoke and wastes wood.
- Make sure your wood stove or fireplace is properly installed, properly vented, and well maintained. Poor ventilation and maintenance can lead to hazardous levels of carbon monoxide and particulate matter in your home.
- Consider upgrading old, less-efficient wood stoves and fireplaces with cleaner and more fuel-efficient EPA-certified models. Visit EPA's Burn Wise Program webpage for more information.
Sources of Wood Smoke | Top
The majority of wood smoke in Utah is the result of residential wood burning in stoves and fireplaces. Wildfires and prescribed burns can be a sporadic but significant source of wood smoke. While not the major source of particulate matter pollution in Utah, wood smoke still contributes to local air quality. Based on data from EPA's National Emissions Inventory, smoke from residential wood burning comprised approximately 5.4% of primary PM2.5 pollution (Figure 1) and 1.2% of primary PM10 pollution (Figure 2) along the Wasatch Front in 2014 (EPA, 2014d; EPA, 2014e).
Figure 1: Sources of primary PM2.5 particulate matter
It is important to note that these data reflect source contributions to primary particles, which are released directly from a source as a particle (e.g., dust from a road or soot from a wood fire). By contrast, secondary particles are formed in complex reactions involving other atmospheric pollutants, such as nitrogen dioxide, sulfur dioxide, and VOCs. Most of the PM2.5 pollution in Utah is from secondary particles, which are not reflected in these graphs (UDAQ, 2014h). Dust (mostly from unpaved roads and construction) is the largest source of primary particles, while motor vehicle exhaust is the largest overall contributor to particle pollution when including both primary and secondary particles.
Figure 2: Sources of primary PM10 particulate matter
The charts above are based on data from EPA's National Emissions Inventory from 2014 for Utah counties in and near the Wasatch Front. An emissions inventory is a database that lists, by source, the amount of air pollutants discharged into the atmosphere of a community during a given time period. The methods used to calculate the emissions inventory may include continuous monitoring to measure actual emissions, extrapolating the results from short-term source emissions tests, and combining published emission factors with known activity levels (EPA, 2014l).
