Health effects of wood smoke

Burning wood adds harmful fine particles and toxics to the air. “The fine particles (or particulate matter (PM)) in wood smoke can trigger asthma attacks in a manner similar to diesel exhaust or secondhand cigarette smoke,” said  Laura Oatman, environmental research scientist from the Minnesota Department of Health (MDH).

Wood smoke contains a hazardous mixture of chemical substances such as carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), dioxin, and inhalable particulate matter (PM). Some of the VOCs are irritating, toxic, and/or cancer causing. One of the biggest human health threats from smoke, indoors or outdoors, comes from PM. Wood smoke PM is composed of wood tars, gases, soot, and ashes. Toxic air pollutants are another potentially important component of wood smoke. A group of air toxics known as polycyclic aromatic hydrocarbons or PAHs include potential carcinogens such as benzo(a)pyrene. The chemical makeup and total amounts of these pollutants depend on how the wood is burned. Conditions that burn wood most completely produce the most usable energy and less of these harmful chemicals. In general, more energy efficient wood burning appliances produce less of these hazardous chemicals. 

Where does particulate matter go?*

* PM10= particulate matter sized at 10 microns; PM 2.5 = partculate matter sized at 2.5 microns.

Most of the particulate matter in wood smoke is smaller than 2.5 microns in diameter.  These are called “fine particles” or PM2.5.  Their small size allows them to go deep into the lungs.  Some of the toxic chemicals from wood smoke combine with the fine particles and are also carried deeper into the lungs.
 
Fine particles can trigger respiratory problems such as asthma attacks and even heart problems. Fine particles are considered especially dangerous for young children with developing lungs, the elderly, and people of all ages who have asthma, bronchitis, other respiratory problems, and cardiovascular disease.

Most of Minnesota’s air quality alerts are caused by fine particles.  Most of the fine particles in outdoor air come from fossil fuel combustion, such as traffic and coal fired power plants.  Poorly controlled wood or other biomass burning, such as forest fires, open burning or inefficient residential wood burning also contributes to fine particles in the air.  Being closer to those sources, especially those emitting pollution near the ground, increases our exposure to those sources of fine particles.  

How big is particle pollution?

Image source: U.S. EPA, Office of Research and Development

Breathing air containing wood smoke can

• Irritate eyes, lungs, throat and sinuses
• Reduce lung function, especially in young children
• Increase severity of existing lung diseases such as asthma, emphysema, pneumonia and bronchitis
• Increase risks of heart attacks

Long term exposure to wood smoke may lead to

• Chronic obstructive lung disease
• Chronic bronchitis
• Increased risks of cancer
• Cardiovascular disease

Smoke from backyard recreational fires also releases harmful air pollution that can penetrate indoors to neighboring homes through intake vents and windows. 

High levels of pollutants leaking from stoves and fireplaces have been measured in some homes with wood burning appliances.  The Environmental Protection Agency (EPA) says the average wood-burning fireplace creates roughly 4,000 times more fine particles than a natural gas furnace.  EPA certifies wood stoves and qualifies fireplaces to provide consumers opportunities to purchase more efficient, cleaner, and safer wood burning products–that also use less wood.  Read more on the Burn Wise (U.S. EPA) web site.

The MPCA strongly encourages those who choose to burn wood to be a good neighbor by building only small hot fires with dry, seasoned wood. It’s also important to properly maintain your stove and chimney.

Always be considerate of family members and neighbors who may have asthma, lung or heart problems. 

For information on best burning methods and a list of what NOT to burn go to Wood Burning Best Practices.

Resources

• Health effects of wood smoke (U.S. EPA)
• Air Quality - Particles and Your Health
• Forest Fire Smoke
• Carbon Monoxide Poisoning in Your Home
• What is Particulate Matter? American Lung Association
• Wood-fired Hydronic Heaters
• Health Effects of Wood Smoke
• Outdoor Wood-Fired Boilers
• National Ambient Air Quality Standards (U.S. EPA)
• Open Burning
• Trash and Wood Burning
• Think Twice About That Outdoor Fire!
• Air Quality Primer for British Columbia Physicians
• Health Effects from Burn Barrels and Backyard Garbage Burning