Chromated copper arsenate (CCA) is a pesticide containing chromium, copper, and arsenic used to treat lumber. CCA protects wood against termites, fungi, and other pests that can degrade wood products or threaten their integrity.
Chromated arsenicals have been used as wood preservative pesticides since the 1940s. In December 2003, CCA manufacturers stopped producing products for residential use.
The EPA (Environmental Protection Agency) does not require removing treated wood and soil. Use this Q&A to learn about CCA disposal and other valuable information.
Arsenic-treated wood results from a chemical process that treats wood with a pesticide/preservative called chromated copper arsenate (CCA). The chemical helps prevent rotting in lumber designed for outdoor use. CCA contained arsenic, chromium, and copper and was widely used for residential purposes in the United States from the 1970s until the U.S. Environmental Protection Agency (EPA) phased it out in 2003.
No – it’s not a good idea to burn 20-year-old treated wood. The smoke and ash could be toxic. In Mississippi, you may dispose of treated lumber in a lined landfill. See more from the MS Dept. of Environmental Quality (MDEQ).
Read the tag. Look for it on the end of the lumber. It may smell like oil or chemicals. Because of the chemicals, the lumber might be a tad larger than regular-sized wood. Color can help you tell if it’s treated; it may be greenish, brown, tan, or olive. Use a swipe test. Find a kit here.
A treated 4×4 will last 20 to 25 years in the ground if soil and climate conditions are favorable. That number could increase to 40 to 75 years if you set the treated 4×4 in a cement ring rather than burying it in soil.
Avoid harsh cleaning products in CCA-treated wood, such as bleach, sodium hydroxide, percarbonate, oxalic acid, and citric acid. Never cut, sand, or power wash old-treated lumber. To reduce potential exposure to chemical residues, apply an oil- or water-based penetrating coating (stain or sealant).
Each piece of pressure-treated wood should carry a tag affixed to the end. The tag’s information helps guide how the lumber’s used.
UC1 – Interior Dry. For treated wood products used in interior construction that are dry and will not contact the ground or exterior weather. A common hazard is deterioration from insects such as termites.
UC2 – Interior Damp. For treated wood products used in interior construction, it may be subject to some moisture but not in contact with the ground. Common deterioration hazards include decay, fungi, and insects.
UC3A – Exterior above ground. Treated wood products used in exterior construction that are coated may be exposed to the full effects of the weather and not in contact with the ground. Common deterioration hazards include decay, fungi, and insects. Application examples: Siding, trim, porches, and fascia.
UC3B – Exterior above ground. For uncoated treated wood products used in exterior construction and not in contact with the ground. Common hazards include decay fungi, insects, and prolonged weather exposure. Application examples: Decking, joists, walkways, and railings.
UC4A – Ground contact. For treated wood products used in construction that contact the ground, freshwater, and are for general use. Common hazards include decay, fungi, and insects. Application examples: Fence posts, structural lumber and timber, utility posts, and deck posts.
UC4B – Ground contact. For treated wood products used in construction that contact the ground for heavy-duty use, such as in severe environments with a high potential for deterioration. Common deterioration hazards include decay fungi, insects, and biodeterioration from saltwater. Application examples: Wood foundations, utility poles, piers, and docks.
UC4C – Ground contact. For treated wood products used in construction that contact the ground for extreme-duty use, such as very severe environments with a high potential for deterioration in critical structural components. Common deterioration hazards include decay fungi, insects, ongoing exposure to weather, and severe biodeterioration from saltwater.
UC5A – Marine use. Treated wood products used near or in salt and brackish northern coastal water are used in marine construction. Common deterioration hazards include marine wood-boring organisms, salt kill, and tidal water. Application examples: pilings, bulkheads, and piers.
UC5B – Marine use. For treated wood products used in marine construction near or in salt and brackish central coastal waters. Common deterioration hazards include marine wood-boring organisms, salt kill, and tidal water. Application examples: pilings, bulkheads, and piers.
UC5C – Marine use. For treated wood products used in marine construction near or in salt and brackish waters on the southern coast and Gulf Coast. Common deterioration hazards include marine wood-boring organisms, salt kill, and tidal water. Application examples: pilings, bulkheads, and piers.
UCFA – Interior fire protection. For treated wood products used in interior construction, fire-protected and not in contact with the ground or exposed to exterior weather. The common hazards of deterioration are fire. Application examples: roof trusses, joists, and paneling.
UCFB – Exterior fire protection. For treated wood products used in interior construction, fire-protected and is not in contact with the ground but may be exposed to full effects of weather. The common hazard is fire-related deterioration. Application examples: vertical exterior walls, roof surfaces, and other drainage system surfaces.