Wood burning smoke is a source of indoor and outdoor pollution that can worsen allergic conditions and asthma. Wood burning smoke sources include wood stoves, fireplaces, forest fires and agricultural fires.

There are more than 11 million wood burning units in American homes, according to the Asthma and Allergy Foundation of America. Wood smoke produces gases and particles in the air that can irritate the respiratory tract and trigger allergic cascades and asthma attacks. This can result in a number of symptoms, including coughing, wheezing and difficulty breathing.

Reducing exposure to smoke from wood stoves, fireplaces, forest fires and agricultural fires is important for people with allergies and asthma. This may mean eliminating indoor wood smoke sources and avoiding exposure to seasonal fires outdoors. Should symptoms occur they may be treated by physician prescribed allergy and asthma medications.

Wood burning smoke is a source of particulate pollution both indoors and outdoors. Wood burning smoke can worsen asthma and exacerbate allergic conditions. It is not usually a threat to people without asthma, allergies or other respiratory conditions.

Wood burning smoke can come from wood stoves, fireplaces, forest fires or agricultural fires. Wood stoves and fireplaces are the primary source of wood smoke pollution indoors, though large smoky forest fires can affect indoor areas in some regions. Forest and agricultural fires are the primary source of wood smoke pollution outdoors.

Wood smoke is made up of a complex mixture of gases (carbon monoxide, nitrogen dioxide and carbon dioxide, among others) and fine particles produced when wood and other organic matter burns. The health threat from smoke comes from these gases and fine particles. The microscopic particles can get into the eyes and respiratory system. Wood smoke exposure can depress immune system activity and cause damage to the cells that protect and cleanse the airways.

The seasonality of exposure to wood burning smoke varies with the source. Wood stoves and fireplaces are used inside and tend to be used during colder months. Forest and agricultural fires tend to occur in the spring and summer months.

The health effects of wood smoke can lead to the worsening of allergy and asthma symptoms. Wood stoves and tobacco smoke are the primary indoor pollutants linked to the development and aggravation of respiratory conditions. In addition to the particles released, combustion always produces water vapor. Water vapor can result in high humidity and wet surfaces. These conditions encourage the growth of other indoor allergens such as dust mites and molds.

Wood smoke can make it more difficult for people to breathe deeply or vigorously, and create coughing, wheezing, chest tightness, irritated sinuses, stinging eyes, runny nose and shortness of breath.

People with respiratory conditions are not the only population affected by wood burning smoke. Children may be more susceptible to smoke because their respiratory systems are still developing. Children breathe more air per pound of body weight than adults, and tend to be more active indoors and outdoors. Research has shown that children who grow up in wood burning households have a significantly higher chance of developing asthma. The elderly and people with preexisting heart conditions are also more susceptible.

Wood smoke produces particles and a variety of gases, all of which may impact allergic conditions and asthma. These substances include:

• Particle pollution. Occurs when tiny particles enter the air from power plant emissions, wood burning and other sources. People can easily inhale these microscopic particles, which then penetrate the body’s defense system. These particles are particularly harmful because they are small enough to settle inside lung tissue, and may pass through the lungs into the bloodstream. Particle pollution has been linked to increased rates of asthma, heart attacks, strokes and lung cancer, as well as reduced life expectancy.
  
  
• Carbon dioxide. A colorless, odorless gas that can deprive the body’s tissues of oxygen. It is commonly generated by wood stoves, cooking and heating systems.
  
  
• Carbon monoxide. An odorless gas that reduces the oxygen–carrying capability of blood. It is the byproduct of indoor fuel–burning appliances such as gas stoves, fireplaces, wood stoves and unvented kerosene or gas space heaters. In high doses, carbon monoxide is lethal. Children are more susceptible to the effects of carbon monoxide exposure.
  
  
• Nitrogen dioxide. An odorless gas that causes bronchial hyperresponsiveness (an exaggerated airway response). It is the byproduct of many of the same products that create carbon monoxide, including indoor fuel–burning appliances such as gas stoves, fireplaces, wood stoves and unvented kerosene or gas space heaters. Children and people with asthma may be more susceptible to the effects of nitrogen dioxide.
  
  
• Formaldehyde. Substance capable of acting as a respiratory irritant.
  
  
• Benzopyrene. Substance capable of causing cancer when inhaled in large amounts.

Many people find that exposure to wood burning smoke triggers or worsens symptoms of other respiratory ailments. These include:

• Asthma. A chronic inflammation of the body’s bronchial (airway) tissues that afflicts millions of people in the United States. People with asthma experience shortness of breath, chest tightness, coughing and wheezing. These symptoms intensify during an asthma attack, which occurs when exposure to allergens or other stimuli further inflame the airways.
  

  

• Allergies.  An allergic cascade is the immune system’s attempt to defend the body from a perceived threat that, in most people, is harmless. During this process, a foreign substance comes into contact with the body and triggers an immune system response that includes symptoms such as itchy eyes, runny nose and sneezing.
  
  

  
  

• Chronic obstructive pulmonary disease (COPD). Respiratory condition that shares one major feature with asthma: airflow limitation. However, whereas asthma is almost always reversible, COPD is usually difficult to treat. COPD causes permanent damage to the air sacs (alveoli) and smaller bronchial tubes of the lungs, and tends to become progressively worse over time.
  
  
• Chronic bronchitis. An inflammation of the lower airway of the respiratory system usually related to smoking or other environmental irritants. The condition is characterized by a moist cough and an overproduction of mucus. Symptoms of chronic bronchitis usually reoccur until the cause of the condition (e.g., cigarette smoke, occupational irritants) is identified and removed.
  
  
• Emphysema. A condition in which the air sacs in the lungs (alveoli) are damaged, interfering with the normal exchange of oxygen and carbon dioxide. People with emphysema experience shortness of breath, a nagging cough (often with mucus) and a gradually worsening ability to exhale.
  
  
• Pneumonia. An infection or inflammation of the lungs that results in the lungs’ air sacs becoming filled with fluid. Pneumonia is caused when bacteria, viruses or other organisms enter the respiratory system and are not attacked effectively by the immune system.

Wood burning smoke is known to exacerbate serious health problems, including asthma, heart attacks, lung cancer, chronic bronchitis, and allergies. Exposure to wood burning smoke may trigger:

• Coughing
• Airway irritation
• Burning eyes
• Rapid, shallow or painful breathing
• Chest discomfort
• Asthma or allergy flare-ups
• Shortness of breath
• Wheezing
• Headaches
• Nausea
• Dizziness
• Sneezing or stuffy nose

To date, there is no standard approach to diagnosing and treating wood smoke–related illnesses. A physician is likely to conduct a complete physical examination and compile a patient medical history and list of symptoms. Diagnosis and care will be targeted toward the underlying condition that the smoke aggravates, such as asthma or a particular allergy.

For people affected by wood burning smoke, steps can be taken to reduce exposure to indoor and outdoor smoke pollutants. Should symptoms occur despite these efforts, physician prescribed allergy or asthma medications can be used.

Those affected by wood burning smoke should make a habit of checking the air quality index, a daily measurement of air–quality levels reported by the U.S. Environmental Protection Agency (EPA). Checking air quality is particularly important if there are regional forest fires. Five major pollutants are tracked:

• Ground–level ozone
• Particle pollution (particulate matter)
• Carbon monoxide
• Sulfur dioxide
• Nitrogen dioxide

Air quality for each pollutant is scored on a scale of 0 to 100, with scores representing a level ranging from “good” to “hazardous.” Anything above 100 is considered unhealthy for asthmatics and allergy sufferers. Air quality is also rated as good, medium, unhealthy for certain groups (such as asthmatics), unhealthy, very unhealthy and hazardous.

Those sensitive to wood smoke should take the following precautions when outdoor air quality is poor:

• Limit time outdoors
• Reduce activity level
• Eliminate using wood stoves and fireplaces indoors

People affected by wood burning smoke should avoid burning wood in their homes. Instead a less polluting heating alternative, such as gas-burning appliances, should be used.

Those who are unwilling or unable to use an alternative can reduce their exposure to harmful emissions by following certain steps. These include:

• Use the cleanest technology available. If wood stoves are used, all wood stoves should be EPA certified and professionally installed. These stoves will emit less pollution.
  
  
• Do not use a malfunctioning wood stove or fireplace. Visible smoke or a constant smoky odor indoors is a sign that the wood stove or fireplace is not working properly. Smoke and soot are signs that pollutants are being released indoors.
  
  
• Maintain the wood stove and fireplace. Wood stoves, chimneys and vents should be professionally inspected and cleaned once a year. This can prevent the buildup of creosote (an oily, black tar that can cause toxic emissions).
  
  
• Use smaller pieces of wood instead of one big piece. Smaller pieces burn more efficiently.
  
  
• Use densified fuel logs. According to the EPA, more expensive, manufactured densified fuel logs can reduce emission by 20 to 30 percent. However, the availability of these logs may be limited in some areas.
  
  
• Use wood alternatives. Wood burning fireplaces can reduce emissions by using decorative gas log inserts.
  
  
• Use seasoned hardwoods (e.g., elm, maple, oak) instead of softwoods (e.g., pine, fir, cedar) in wood stoves and fireplaces. Hardwoods may burn hotter and deposit less creosote in chimneys and pipes. However, while many experts recommend this practice, there is currently no laboratory research that conclusively demonstrates the advantage of using hardwoods over softwoods.
  
  
• Do not use green (unseasoned) or wet wood because they produce more moisture, smoke and creosote.
  
  
• Never burn scrap–wood or stained, painted or treated wood as they could release toxic pollutants like arsenic or lead.
  
  
• Never burn plastic, charcoal or colored papers as they also release pollutants.
  
  
• Keep windows open. Windows can be kept open for ventilation while a wood–burning stove or fireplace is used. However, this may not be a good idea if outdoor pollen levels are high.
  
  
• Purchase carbon monoxide detectors. Carbon monoxide detectors are available that will sound an alarm if dangerous levels of carbon monoxide accumulate indoors.

Additional steps for reducing exposure include:

• Try to limit exercise or other strenuous outdoor activities when there are forest fires burning in the region. Exercise involves deep inhalation, which brings pollutants more deeply into the lungs. Also, people exercising tend to breathe through the mouth, where incoming air is not filtered as effectively as it is when breathing through the nose.
  
  
• Reduce particle pollution in the home by not smoking, venting all gas or other combustion appliances directly to the outdoors and not burning wood in the stove or fireplace.
  
  
• Use HEPA filters to capture airborne particles and common allergens in the home. These filters should be regularly maintained to get optimal air quality.
  

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• When a forest or agricultural fire is burning outdoors, avoid using anything that burns including wood stoves, fireplaces and candles indoors. When outdoor air quality is poor it is important to avoid compromising indoor air quality. Vacuuming stirs up particles already indoors and should be avoided at these times as well.

It is unknown whether burning wood may release pollen. People with pollen allergies should avoid burning any wood that releases pollen to which they are allergic. For example, a person with a cedar pollen allergy should not burn cedar in their wood stove or fireplace. This person should also avoid exposure to smoke during a forest fire if cedar trees are present in the area.

Since 1992 the Environmental Protection Agency (EPA) has certified all wood stoves for use indoors to ensure that emissions are not harmful. However, the standards under which the stoves are actually used by consumers do not always match those of the certification process. The EPA standard for wood stove emission certification requires that a successful coal bed preparation be used to produce low burn rates. Failure to use this method can result in significant differences in indoor emissions. However, there is no way to monitor home emissions or ensure that proper preparation methods are used in the home. People using indoor wood burning stoves are encouraged to use the techniques recommended by the EPA.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to wood burning smoke:

1. Do my symptoms indicate a sensitivity to wood burning smoke?
   
   
2. What are my treatment options?
   
   
3. What should I do when symptoms develop following exposure to wood smoke?
   
   
4. How can I lower my exposure to wood burning smoke?
   
   
5. Where can I find the daily air quality level for my area?
   
   
6. Are some types of wood better for me to use than others?
   
   
7. Are manufactured densified fuel logs a safer option for me?
   
   
8. I have a fireplace in my home. Are my children more likely to have respiratory problems?