Some people believe that wood smoke is only an issue if you have asthma or another lung disease. But wood smoke is bad for everyone, especially children. Wood smoke pollution has been linked to a wide range of health outcomes, including heart attacks and dementia.
If you are not a smoker, breathing wood smoke is one of the most damaging things you can do to your health.
If you are a smoker, breathing wood smoke can reduce your lung function even more than from smoking alone, as well as increase your risk of smoking-related diseases such as chronic bronchitis and COPD.
Wood smoke particles are mostly in the fine and ultrafine size range that are most easily inhaled and most damaging to health.
Wood Heating Is Linked to Premature Deaths
Pollution from residential wood burning is linked to premature deaths.
In Europe alone, for example, the burning of solid fuel (mostly wood) is estimated to contribute to the premature deaths of approximately 60,000 people a year (PDF).
A study centered on Nordic cities estimated that residential wood burning caused around 78 premature deaths each year in Copenhagen and 232 in Oslo.
In Armidale, Australia, a city with a population of around 24,500, it has been estimated that 14 people each year die prematurely from pollution caused by residential wood heating.
Wood Smoke vs. Traffic Pollution-Related Death Rates
A study comparing air pollution and death rates between Santiago, Chile (where most particulates are from traffic) and Temuco, Chile (where the majority is from wood burning), found evidence that residents of Temuco faced a higher risk of death (PDF) from cardiac and respiratory causes than in Santiago, even when particulate levels in the two cities were comparable.
Temuco had much higher levels of polycyclic aromatic hydrocarbons (PAHs) and other airborne toxins. Also, the size of the particles was smaller in wood-burning Temuco. “Finer particles penetrate more deeply into the respiratory system, even entering the bloodstream and thus the cardiovascular system and other organs, which could be affected by PAHs and other airborne toxins.”
Reducing Wood Smoke Lowered Death Rate
A community that reduced wood smoke pollution also lowered its death rate.
Launceston, Australia, conducted a wood smoke reduction program that encouraged residents to switch from wood stoves to electric heating. Wintertime deaths from respiratory disease dropped by 28%, and from cardiovascular disease by 20%. Year-round, for men, the reductions were 23% (respiratory), 18% (cardiovascular) and 11.4% (all deaths).
Based on a population of 100,000, the cost of cleaning up the air was less than A$21 per resident.
Wood Burning and Lung Diseases
Wood smoke increases airway irritation that leads to coughing and difficulty breathing. It damages lung epithelial cells. It aggravates asthma and can increase its severity. It can decrease lung function and lead to the development of chronic bronchitis and conditions such as chronic obstructive pulmonary disease (COPD).
More Wood Stoves, More COPD Cases?
In 2015, an article in the Canadian Medical Association Journal suggested that an increase in cases of COPD may be due to an increased use of wood stoves. Dr. Kenneth Chapman, President of the Canadian Network for Respiratory Care and a professor of medicine at the University of Toronto stated:
Tiny particulates, produced from combusting wood are dangerous, especially for people with pre-existing respiratory issues. It’s the same thing that’s harmful about tobacco smoke—minus the nicotine. There are volatile gases that you don’t want to inhale and can irritate the airway and lungs.
A study of women hospitalized with COPD in Barcelona found “a strong association between wood or charcoal smoke exposure and chronic obstructive pulmonary disease, supporting its existence not only in developing countries, but also in European countries, such as Spain.
Allergies and Altered Immune Function
Exposure to wood smoke, as well as to traffic pollution, has been linked to worsened allergic reactions. It is also associated with lower immune function. Animal studies have demonstrated that short-term, repeated exposure to wood smoke can compromise the lungs’ ability to fight off infections.
It has been shown that patients without rheumatoid arthritis who have wood smoke-induced COPD have much higher rates of an antibody associated with rheumatoid arthritis than those who have tobacco-related COPD or healthy controls. This may suggest that wood smoke is also a risk factor for triggering autoimmune diseases.
Wood Smoke and Heart Attacks
As we mention on our Particle Pollution page, exposure to fine particle pollution is linked to heart attacks.
However, there is evidence that when the particulate matter comes from wood smoke, rather than from other sources, the risk is even higher.
Raised Heart Attack Risk for Seniors
A study found that when particle pollution from residential wood burning was at its highest, the risk of heart attacks in seniors rose by 19%.
According to McGill University professor Scott Weichenthal, lead author of the study:
We noticed that the association was stronger when more of the air pollution came from wood burning. This suggests that the source of pollution matters and that all particulate air pollution is perhaps not equally harmful when it comes to cardiovascular disease.
More Symptoms in Heart Attack Survivors
A study in Germany of air pollution constituents and symptoms in heart attack survivors found evidence that compounds related to wood burning are particularly harmful.
Wood smoke also stiffens arteries and reduces heart rate variability. Reduced heart rate variability has been associated with sudden cardiac death.
Inflammation and Blood Clotting
Short-term exposure to wood smoke in healthy adults has been linked to increased levels of inflammation and effects on blood clotting. “Relatively low levels” of wood smoke exposure have also been associated with raised biomarkers in blood, breath and urine indicating effects on airways.
It has also been shown in a laboratory experiment that the free radicals in wood smoke remain chemically active forty times longer than those from cigarette smoke. (Free radicals play a major part in the development of chronic and degenerative illnesses such as cancer, autoimmune disorders, cataracts, rheumatoid arthritis, cardiovascular diseases and neurodegenerative diseases.)
Wood Burning Linked to Dementia Risk
As we note elsewhere, exposure to fine particle pollution is recognized as a risk factor in the development of dementia.
Researchers in Sweden studied a population living in an area where PM2.5 came mostly from residential wood burning. They found that those who lived in an area with a 1 µg/m3 increase in PM2.5 due to residential wood burning had a 55% higher likelihood of developing dementia compared to those who were not living in an area polluted by wood smoke. Those who had a wood stove in their home and lived in neighborhoods where wood burning was common were 74% more likely to develop dementia over the course of the study.
Damages DNA More Than Traffic Exhaust
Wood smoke has been found to produce high levels of free radicals and DNA damage, as well as to promote inflammatory and oxidative stress response gene expression in human cells. Compared to diesel exhaust particles, wood smoke particles were found to cause increased levels of DNA strand breaks in a laboratory study.
Another study similarly found that particulate matter from wood smoke “generates more DNA damage than traffic-generated (particulate matter) per unit mass in human cell lines, possibly due to the high level of polycyclic aromatic hydrocarbons” in wood smoke. According to the authors of the study:
This suggests that exposure to wood smoke particulate matter might be more hazardous than particulate matter collected from vehicle exhaust with respect to development of lung cancer.
Wood Smoke and Cancer Risk
Wood smoke contains chemicals that are listed as known and suspected carcinogens by the International Agency for Research on Cancer (IARC), as well as other chemicals that are classified as hazardous air pollutants. (For more information on chemicals in wood smoke, please see our Toxins page).
More Carcinogenic Than Cigarette Smoke
Extracts of particulate matter containing “substantial quantities of wood smoke” have been found to be 30 times more potent at inducing tumors than cigarette smoke condensate (PDF) in an animal study.
Carcinogenic Pollution Linked to Wood Burning
A study in Athens, Greece, found that residential wood burning is “a considerable source of carcinogenic PAHs in one of the most populated regions of the Mediterranean,” responsible for nearly half the annual carcinogenic potential from these compounds in the air. “This can result in a large number of excess cancer cases due to biomass burning-related high PM levels.”
The researchers involved in the study pointed out that while the analysis was done in Athens, the results were not unusual. Carcinogenic pollution from residential wood heating is a significant problem in cities throughout Europe.
Pollution from wood stoves and fireplaces has been found to be the top cancer risk in Oregon’s air. A study from Seattle found, as well, that pollution from wood burning is a primary airborne cancer risk. The situation is likely similar in other places where wood stove use is common.
Focus on Wood Heating to Lower Cancer Risk
A report in Canada found that wood smoke from residential wood heating, more than emissions from industrial sources, was “an important source of cancer-related pollutants” and recommended that, in some regions of the country, pollution reduction efforts should focus on residential wood burning for heat in order to lower cancer risk.
Lung and Throat Cancer Risk
Wood smoke is associated with the development of lung cancer. For example, in an article on the Medical Journal of Australia’s InSight+ website, respiratory physician Dr. James Markos said of breathing air polluted by wood stoves:
It is identical to the risk of lung cancer from passive smoking. So, if you live in a smoky hollow, you are playing Russian roulette with whether you might end up with lung cancer after 20 or more years.
An association has also been found with wood smoke and carcinomas of the mouth, pharynx, and larynx.
Children Absorb More Carcinogens
It has also been noted that children, who absorb more of the carcinogenic polycyclic aromatic hydrocarbons (PAHs) from wood smoke than adults due to their size and physiological differences, have a higher lifetime risk of lung cancer from inhaling wood smoke than adults.