(Click on Blue Highlights to go to further information)
All burning creates harmful by-products of combustion, resulting in air pollution. Materials on the low end of the energy scale such as wood and charcoal create the most pollution. Other recreational solid fuel sources are incense, candles, wax logs, charcoal grills and tobacco. Sources on the high end of the energy scale or ladder, such as natural gas and propane burn very cleanly resulting in very little air pollution. (Caution: though small in amount, these combustion by-products are also dangerous and need to be completely vented from living spaces!) The basic components of wood smoke pollutants are:
Particulates: PM10, PM2.5, Nanoparticulate: Tiny particles suspended in the air that are too small to be filtered out, and thus become embedded deep within the lungs. The most injurious are particles classified as PM2.5. They are 2.5 microns in diameter or less. Wood smoke PM2.5 contains creosote, soot, and ash. Most smoke particles average less than one micron (one millionth of a meter), allowing them to remain airborne for 3 weeks. The particles are efficient vehicles for transporting toxic gases, bacteria and viruses deep into the lungs where they pass into the blood stream. Inhalation of PM25 causes coughing, irritation and permanent scarring and damage to the lungs resulting in decreased lung function and increases in respiratory illness. It contributes to cancer, heart disease and changes in DNA leading to autoimmune disease. It causes sudden, premature death. These effects become significant at averages less than 40 micrograms per cubic meter. Smoke from just one fireplace burning has been found to cause particulate levels to exceed 200 ug/m3 in the outdoor air surrounding the neighboring property. These particles are so small that they filter into your home even with all the doors and windows closed.
Carcinogens: Polycyclic Aromatic Hydrocarbons (PAH): Residential wood burning is the source of 50% of airborne Polynuclear Organic Material (POM) in the U.S. POMs contain a group of compounds (PAHs) which include many Class A carcinogens, the most carcinogenic materials known to exist. Air pollution measurements in a residential neighborhood on Christmas Day (the most wood smoke polluted day) showed early morning background levels of PAHs of 20ng/m3. The level increased as wood burning began, peaking at over 2000 ng/m3. The U.S. EPA estimates the cancer risk from wood smoke is twelve times greater than that from equal amounts of tobacco smoke. Wood burning also creates dioxins.
Carbon Monoxide :An odorless gas resulting from all burning but produced in large amounts when burning takes place with reduced oxygen, such as in wood stoves. Even small amounts in the air reduce the body's ability to transport oxygen, constrict muscles and blood vessels, stress the heart, and result in feeling cold, fatigued and nauseated. High CO levels are found indoors where wood is burned.
Respiratory Irritants and Toxins: There are over 100 different chemicals and compound groups in emissions from burning wood. In addition to those noted above there are chemicals known to be toxic such as formaldehyde, propionaldehyde, acetaldehyde, isobutyraldehyde, phenol, cresols. Nitrogen dioxide which is released impairs the respiratory system and reduces its ability to fight infection. This combines with the organic compounds to form ozone which makes breathing difficult. High levels of Volatile Organic Compounds are found in the emissions of lawn equipment, charcoal grills and many personal care and cleaning products.
"With the exception of some very low California readings, all measurements of wood ash with fallout-cesium exceeded - some by 100 times or more - the levels of radioactive cesium that may be released from nuclear plants (about 100 picocuries per kilogram of sludge). Wood ash-cesium levels were especially high in the Northeast" [Science News, 1991]