CCA lumber is wood that has been pressure-treated with chromated copper arsenate, a chemical preservative containing chromium, copper, and arsenic. It was the standard for outdoor residential wood projects like decks, fences, and playsets for decades, but manufacturers voluntarily stopped producing it for homeowner use in December 2003 due to concerns about arsenic exposure. CCA-treated wood is still manufactured today for specific industrial and agricultural applications.
What CCA Treatment Contains
The most common formulation, known as CCA Type C, is made up of 47.5% chromic acid, 18.5% cupric oxide, and 34% arsenic pentoxide. Each ingredient serves a distinct purpose. The copper acts as a fungicide, preventing the wood from rotting. The arsenic works as an insecticide, making the wood toxic to termites and other wood-boring insects. The chromium binds the copper and arsenic to the wood fibers so they don’t wash out immediately.
During pressure treatment, the wood is placed in a sealed chamber and the CCA solution is forced deep into the grain under high pressure. This process leaves copper, chromium, and arsenic concentrations in the wood ranging from 1,000 to 5,000 milligrams per kilogram. The result is wood with a distinctive greenish tint that resists decay for decades, even in direct ground contact or wet conditions.
Why CCA Was Phased Out for Residential Use
Despite its effectiveness, CCA lumber poses a real exposure risk. Arsenic gradually migrates to the wood’s surface over time, where it can transfer to skin on contact. Testing by the Connecticut Agricultural Experiment Station found that new CCA lumber from retail yards had an average of 40 micrograms of arsenic per 100 square centimeters of surface. Older playground equipment tested lower, averaging about 8.8 micrograms per 100 square centimeters, but utility poles that had weathered for years averaged 105 micrograms, showing that leaching patterns vary widely.
Soil contamination is the other major concern. Beneath CCA-treated decks, arsenic levels in soil ranged from 3 to 350 milligrams per kilogram, with an average of 76 mg/kg. For comparison, control soil samples from areas without treated wood averaged just 4 mg/kg of arsenic. Copper and chromium levels beneath decks were similarly elevated, running roughly four times higher than background levels.
These findings drove the EPA to negotiate a voluntary phase-out with manufacturers. As of 2004, CCA-treated wood could no longer be sold for residential projects like decks, playsets, picnic tables, or landscaping timbers.
Where CCA Lumber Is Still Used
CCA treatment didn’t disappear entirely. It remains approved for commercial and industrial applications where durability in harsh conditions outweighs the exposure concerns that matter most in residential settings. You’ll still find CCA-treated wood in utility poles, highway guardrail posts, marine pilings, and agricultural fence posts. Permanent wood foundations and building poles can also be treated with CCA at specific concentrations under the American Wood Protection Association’s standards.
For the residential projects CCA once dominated, alternative preservatives have taken over. The most common replacements use copper combined with organic compounds rather than arsenic or chromium. These alternatives still give the wood a greenish or brownish color and provide strong rot and insect resistance, but without the arsenic exposure risk.
If You Already Have CCA-Treated Wood
Millions of decks, fences, and structures built before 2004 still contain CCA-treated lumber, and there was never a requirement to remove them. If you have an older deck or fence that has that characteristic green-gray look of pressure-treated wood, it’s likely CCA-treated. The wood itself remains structurally sound for a long time, often 20 to 40 years or more.
Applying a penetrating sealant or stain can reduce the amount of arsenic that reaches the surface. Oil-based penetrating stains are generally more effective than film-forming coatings like paint, which can crack and peel. Reapplying every one to two years helps maintain a barrier between the chemicals and anyone touching the wood. Washing your hands after contact with the wood, especially before eating, is a simple step that meaningfully reduces exposure.
Sanding CCA wood creates toxic dust, so if you’re refinishing an older deck, wear a respirator rated for particulates and work in a well-ventilated area. Collect the sawdust rather than letting it blow into the yard.
How to Dispose of CCA Wood Safely
The single most important rule: never burn CCA-treated wood. Burning releases arsenic and chromium into the smoke and concentrates them in the ash, creating a far more dangerous exposure than the intact wood ever would. A single tablespoon of ash from burned CCA wood can contain a lethal dose of arsenic.
Chipping or composting CCA wood is also prohibited because it releases the chemicals into soil. The proper disposal method is sending it to a landfill, but state and local regulations vary on how this should be handled. Some areas require CCA wood to go to lined landfills or hazardous waste facilities rather than standard municipal dumps. Checking with your local waste authority before hauling old CCA lumber to the curb saves you a potential fine and keeps the chemicals contained.
How to Tell if Wood Is CCA-Treated
CCA-treated wood typically has a greenish tint when new, fading to a silvery gray as it weathers over the years. Many pieces carry an end tag or ink stamp from the treatment facility listing the preservative type and the retention level. If you’re looking at an older structure with no visible tags, the age is your best clue: pressure-treated wood installed before 2004 in a residential setting was almost certainly CCA. Wood installed after that date most likely uses one of the copper-based alternatives.
For a definitive answer, inexpensive arsenic test kits designed for wood surfaces are available online and at some hardware stores. You swab the wood and the kit indicates whether arsenic is present. This can be useful if you’re buying a home with an older deck or planning renovations that would involve cutting into the wood.