Treated lumber is wood infused with chemical preservatives to protect it from rot, fungi, and insects, making it suitable for outdoor use like decking and fencing. Burning treated lumber is dangerous and must be avoided because the high heat converts these chemicals into toxic smoke and ash. This process poses severe health risks and contaminates the environment.
The Toxic Chemicals Released During Combustion
Treated lumber contains heavy metals and organic compounds released into the air when heated. Older pressure-treated wood often contains Chromated Copper Arsenate (CCA), a preservative blend of chromium, copper, and arsenic. Although CCA is no longer used for most residential applications, it remains in many existing structures and is highly hazardous if burned. When CCA-treated wood is combusted, the heavy metals are not destroyed; arsenic vaporizes, and chromium and copper become concentrated in the resulting ash.
Newer residential lumber uses copper-based alternatives such as Alkaline Copper Quaternary (ACQ) and Copper Azole (CA). These treatments still contain high levels of copper, which releases toxic fumes and particulate matter upon burning. Industrial-grade treated wood, such as railroad ties or utility poles, may contain oil-based preservatives like creosote or pentachlorophenol (penta). Burning these materials releases polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs), which are known carcinogens.
Immediate and Long-Term Health Effects of Exposure
Exposure to the smoke from burning treated wood causes a range of immediate health issues. Inhaling the concentrated chemical fumes may lead to symptoms like severe respiratory irritation, intense headaches, and nausea. The microscopic particulate matter (PM2.5) in the smoke penetrates deep into the lungs, exacerbating existing conditions like asthma or chronic obstructive pulmonary disease (COPD).
Chronic or repeated exposure to heavy metals in the smoke and ash presents serious long-term health risks. Arsenic and chromium inhalation are associated with an increased risk of various cancers, particularly lung cancer. Neurological damage and skin lesions are also potential consequences of prolonged exposure to these toxins. Children and pets are particularly susceptible to exposure because they absorb toxins more readily due to their smaller body mass and often play near settled toxic ash residues.
How to Identify Treated Lumber
Visual and olfactory cues help identify treated wood before it is accidentally burned. Freshly treated lumber often has a distinct greenish or brownish tint due to the copper compounds used in preservation. Older treated wood may weather to gray or tan, but a fresh cut often reveals the tell-tale green hue beneath the surface. A strong chemical or slightly oily odor is another indicator that wood has been treated with preservatives like creosote or ACQ.
The most reliable method is checking for manufacturer stamps or tags, typically found on the end grain of the board. These stamps use abbreviations like “ACQ,” “CCA,” or “CA” to indicate the preservative used. They may also include phrases like “Ground Contact” or “EPA Registered.” Additionally, small, evenly spaced incisions or slits on the wood’s surface are marks left by the pressure process used to force chemicals deep into the wood fibers.
Safe and Legal Disposal Methods
Treated wood must never be disposed of with regular household waste or yard debris. State and local regulations often prohibit the open burning of treated lumber due to the high toxicity of the resulting smoke and ash. Burning treated wood is hazardous to health and can also lead to significant fines.
The proper disposal process requires taking the material to a designated facility equipped to handle chemically treated waste. Contact your local waste management authority or public works department for specific guidance. In many jurisdictions, treated wood waste must be taken to landfills authorized to accept construction and demolition debris containing preservatives. If the wood is still structurally sound, salvaging and reusing it for another appropriate outdoor project is the best option to keep the material out of the waste stream entirely.