Health and Emissions
While many improvements are being made to residential wood combustion technologies, older, less efficient units are still in widespread use. According to some estimates, more than three quarters of all wood stoves currently in use in the United States were made before 1991, when the Environmental Protection Agency's (EPA) current combustion standards went into effect. These older units release significantly more harmful pollutants into the air.
Outdoor wood boilers (OWBs), which have so far avoided Federal regulation, release four to 12 times more emissions than wood stoves and 10 to 20 times more emissions than EPA-certified wood stoves (see * below for an official definition of outdoor wood boilers). The significant environmental and health impacts of OWBs result from excess smoke caused by frequent on-off cycling, oxygen-deprived burning conditions, and low smoke stacks. And, because of their large fireboxes and the fact that they are situated outside, they are prone to abuse, with users commonly burning wet wood and leaves and even garbage, animal carcasses, old asphalt roofing tiles, and other extremely harmful materials.
The New York State Department of Health web site has information related to OWBs, including for residents considering buying these units, and for anyone affected by a neighbors OWB smoke.
Fireplaces, pellet stoves, and wood-burning cook stoves, like OWBs, are not currently regulated and there is a wide range of how polluting and inefficient they are. Along with new source performance standards (NSPS) being worked on by the EPA to tighten emissions standards for wood stoves, they are currently taking another look at whether to regulate these other types of combustion equipment, with a decision and, possibly, some standards expected by 2011.
Fine particulate matter
Wood combustion is a major contributor to indoor and outdoor air pollution, mainly in the form of fine particulate matter. Also known as PM2.5, fine particulate matter is smaller than 2.5 micrometers in size. Its small size allows the pollutants to bypass the primary airway filters and penetrate into the deep lungs. Short-term exposure to PM2.5 leads to coughing, sneezing, runny nose, heavy breathing, and irritation in the eyes, nose, throat, and lungs, and can have serious health effects in people with asthma, heart disease, or other underlying health issues. Long-term exposure can lead to asthma, chronic bronchitis, reduced lung function, increased cancer risk, reduced immune function, and heart disease, and has adverse effects on the physical development of young children.
Modified from www.burningissues.org/compemmis-part-sources.htm, Mary J. Rozenberg, Burning Issues/ Clean Air Revival, Inc., 12/1/98
Among the multitude of uncombusted particles created when wood is burned, polycyclic aromatic hydrocarbons (PAH) are among the most harmful. This dangerous mixture of particles is known to cause high rates of birth defects, lower birth weights, difficulty reproducing, and weakened immune system. Both the U.S. Department of Health and Human Services and the International Agency for Research on Cancer deem PAH a probable human carcinogen.
Another uncombusted pollutant, carbon monoxide (CO), is a toxic gas capable of causing exhaustion, chest pains, and nausea in low concentrations. High concentrations of CO lead to headaches, angina, impaired vision and coordination, mental disorder, and can be deadly.
Benzene, even in low amounts can, over time, disrupt the immune and reproductive systems and increase the risk of cancer and leukemia. High concentrations show similar symptoms to CO toxicity, in addition to tremors and increased heart rate.
Chlorinated dibenzo-p-dioxins (CDD) are chlorine-containing compounds present in treated wood, plastics, pesticides, and other materials that should never be burned, but often are. CDDs have serious health effects, including skin disease, changes in reproductive system, and clear alteration to blood, urine, and liver chemistry.
Another common combustion byproduct, nitrogen oxide, causes pulmonary edema, bronchoconstriction, and elevated infection rates.
Reduce your risk
The most important things you can do to reduce your risk from wood smoke are to upgrade to the most energy-efficient, lowest emitting combustion technologies available and to burn only clean, dry wood. Clearly, burning plastics, treated, painted or stained wood, or material containing glue, including cardboard and envelopes as well as wood, releases toxic chemicals and should be avoided at all costs. But even burning wood that isn't properly dried can result in greatly increased levels of harmful emissions. Visit our Best Burn Practices and Proper Maintenance pages for more information.
*The New York State Department of Environmental Conservation's definition of an outdoor wood boiler is "A fuel burning device that (a) is designed to burn wood or other fuels; (b) is specified by the manufacturer for outdoor installation or installation in structures not normally occupied by humans; and (c) is used to heat building space and/or water via the distribution, typically through pipes, of a gas or liquid (e.g., water or water/antifreeze mixture) heated in the device."