Chromated Copper Arsenate (CCA) Treated Wood
Introduction
This document provides an update of current information available on Chromated Copper Arsenate (CCA) used as a preservative for wood. Health Canada’s Pest Management Regulatory Agency (PMRA) and the United States Environmental Protection Agency (U.S. EPA) continue to work together towards completing the re-evaluation of CCA. The re-evaluation is expected to be completed in late 2003, at which time this fact sheet will be updated to reflect the conclusions of the re-evaluation.
What is CCA and where is it used?
CCA is a water-borne preservative containing arsenic, chromium and copper. It is used for the long-term protection of wood against attack by fungi, insects and marine borers. Applying wood preservatives extends the productive life of wood, and helps reduce demand for forest resources. CCA-treated wood is used primarily for structures intended for outdoor settings and is commonly used in residential construction such as playground structures, fences, gazebos and decks. It is also used for industrial uses such as utility and construction poles, marine timbers and pilings.
How is wood treated with CCA?
Wood is treated in commercial plants by trained workers, using pressure to force the preservative solution into the wood. Prior to the wood being treated, small cuts are made into its surface to improve the penetration of the preservative solution. The wood is stacked and loaded into a sealed chamber, where the wood’s natural moisture is removed by vacuum. The chamber is then pressurized, forcing the CCA preservative solution into the wood. A vacuum is then used to extract any excess solution. The wood is removed from the chamber and left to dry naturally or an accelerated chemical fixation process is used, during which time the wood preservative binds to the wood.
How much longer will CCA-treated wood be available for use? Why?
In response to ongoing changes in the residential treated wood market, the wood treatment industry in Canada is making a voluntary transition away from the use of CCA to treat wood for use in residential applications by the end of 2003. Remaining stocks of wood treated with CCA before December 31, 2003 can continue to be sold and used for residential applications. Existing structures built from CCA-treated wood are not affected by this action.
CCA will still be available to treat wood for industrial uses.
Are there alternatives to CCA-treated wood?
Naturally decay-resistant woods such as cedar and redwood are available. Depending on the application, non-wood alternatives such as plastics, metal, concrete, composite materials and outdoor fabrics can also be used.
Where the use of treated wood is preferred, currently registered alternative products include ammoniacal copper quat (ACQ) (ammonia-based with DDAC), alkaline copper quat (ACQ) (amine-based with ADBAC), ammoniacal copper citrate, and copper azole. Talk to your wood retailer about the availability of these alternatives.
Does CCA-treated wood present health risks?
To date, Health Canada and the U.S. EPA have not concluded that CCA-treated wood poses any unreasonable risk to the public or the environment. Nevertheless, arsenic is a known human carcinogen and so Health Canada believes that any reduction in the levels of potential exposure to arsenic is desirable.
As indicated previously, Health Canada’s Pest Management Regulatory Agency (PMRA) and the U.S. EPA are actively co-operating to re-evaluate the potential human health and environmental risks of CCA. Current risk assessment methods are being employed in this re-evaluation, which include consideration of workers’ exposure and a special focus on sensitive sub-populations such as children who may come in contact with treated wood. Completion of the re-evaluation is targeted for late 2003.
Recently, the U.S. Consumer Product Safety Commission (CPSC) released a risk assessment of CCA-treated wood on playground structures. This assessment concluded that children playing on playground equipment built with CCA-treated wood may have a slightly increased risk of developing cancer. However, at this time, no further action has been recommended by the CPSC. For further updates, visit the CPSC Web site.
The PMRA and U.S. EPA re-evaluation of CCA-treated wood is expected to be completed in late 2003. This involves a rigorous and complex scientific assessment that considers all relevant information, including the CPSC report, uses the most advanced methods available, and will be the most comprehensive risk assessment available for determining the potential risks to children posed by arsenic exposure from CCA-treated wood. This approach taken by the PMRA and U.S. EPA is based on recommendations from a 2001 meeting of the Scientific Advisory Panel (SAP). The SAP comprises researchers/academics who have expertise in the specific area of interest.
The regulatory agencies are also continuing to investigate the effectiveness of coatings in reducing any potential risk associated with CCA-treated wood.
How can I tell if my deck has been constructed with CCA-treated wood?
Freshly treated wood, if not coated, has a greenish tint which fades over time. As a practical matter, CCA has been the principal chemical used to treat wood for decks and other outdoor uses around the home. Generally, if your deck has not been constructed with redwood or cedar, then the deck was probably constructed from CCA-treated wood. Alternatively, if you know who constructed the deck, you may want to contact them and ask.
Wood treated with the new copper-based wood preservatives will look the same as CCA-treated wood. Whenever using and handling any treated wood, it is good practice to follow the same precautions as recommended for CCA-treated wood.
Does arsenic leach out of treated wood?
Scientific studies suggest that arsenic, over time, slowly leaches from CCA-treated wood products. The amount and rate at which arsenic leaches depends on many factors including (but not exclusively) the species of wood, amount of rain, the pH of the rain and soil in contact with the wood, and the age of the structure. In general, the concentration of arsenic in soil leached from treated wood decreases rapidly within a short distance from the treated wood. Small amounts of arsenic may also be dislodged from the surface of wood.
Is it safe for children to play on structures made with CCA-treated wood?
As part of its re-evaluation of CCA, the PMRA is conducting a thorough scientific assessment of risks to children playing on CCA-treated wood, which takes into account any special sensitivities they may have and unique behaviours, such as hand-to-mouth transfer. As mentioned earlier, this re-evaluation will be complete in late 2003.
As always, parents should manage risks to their children and follow basic good hygiene practices such as washing hands thoroughly after activities involving contact with various surfaces/materials including treated wood, animals and soil, especially prior to eating and drinking.
Do I need to remove my existing structures built from CCA-treated wood?
At present, the PMRA has not concluded that CCA-treated wood poses any unreasonable risk to public health or the environment and is therefore not recommending removal of existing structures. Concerned citizens may want to take extra precautions, however, by applying a coating to exposed surfaces on a regular basis (see below for more information on coating structures).
What types of coatings are most effective?
If consumers have concerns about existing CCA-treated wood structures on their property (e.g., decks or fences), they may consider applying a coating to the wood. While available data are very limited, some studies suggest that applying certain penetrating coatings (e.g., oil-based, semi-transparent stains) on a regular basis (e.g., once a year or every other year depending upon wear and weathering) may reduce the migration of wood preservative chemicals from CCA-treated wood.
In selecting a finish, consumers should be aware that, in some cases, “film-forming” or nonpenetrating stains (e.g., latex semitransparent, latex opaque, and oil-based opaque stains) on outdoor surfaces such as decks and fences are not recommended, as subsequent peeling and flaking may ultimately have an impact on durability as well as exposure to the preservatives in the wood. Talk with your local hardware store about available coatings. The use of deck washes or bleaches on CCA-treated wood is also not recommended, as it is likely to accelerate leaching.
Food contact surfaces/picnic tables
Do not put food in direct contact with CCA-treated wood. When eating at picnic tables, ensure that food is consumed from plates and not directly from the surface of the table or consider using a plastic table cloth as a barrier.
What precautions should I take when working with CCA-treated wood?
Basic precautions to be taken when working with CCA-treated wood are:
- Only purchase CCA-treated wood that is visibly clean and free of surface residues of the preservative; this wood may contain dislodgeable toxic chemicals.
- Wear gloves and long sleeves when handling treated wood.
- Wear a dust mask, eye protection, gloves and long sleeves when sawing, sanding, shaping or otherwise machining treated wood to avoid skin contact with or inhalation of sawdust.
- Saw, sand and machine CCA-treated wood outdoors.
- Wash hands and other exposed skin after contact, and before eating, drinking or smoking.
- Wash clothes before re-wearing. Wash separately from other clothing.
- After construction, all end-cuts, sawdust and construction debris should be cleaned up and disposed of in accordance with local regulations.
What should I do if I suspect poisoning from working with treated wood?
Unless you are exposed to burning treated wood which creates an inhalation hazard, it is unlikely that working with treated wood would result in enough exposure to cause symptoms (See precautions above). However, if you do suspect poisoning, you should seek medical attention.
Can CCA-treated wood be used in direct contact with drinking water?
No. The use of CCA-treated wood in direct contact with drinking water is unacceptable.
Can sawdust or ‘chipped’ wood from CCA-treated wood be composted or used for mulch?
No. Do not compost or mulch sawdust or remnants from CCA-treated wood.
Can I burn CCA-treated wood?
No. Burning CCA-treated wood is unacceptable. Burning this wood concentrates and releases the preservative chemicals in the ash and smoke of a fire.
Additional information on the proper handling and disposal of preservative-treated wood products can be found at www.ccasafetyinfo.ca.
What are the environmental hazards or concerns associated with CCA?
The environmental hazards of CCA-treated wood are related to the high toxicity of copper, chromium and arsenic to non-target organisms in freshwater and marine environments. The potential risk depends on the exposure, i.e., the amount of CCA being leached from treated wood into the aquatic ecosystem, directly or indirectly.
In general, small ground-based structures made from CCA-treated wood that is properly treated and fixed are unlikely to cause any environmental hazard. There are some data that indicate some sealants can reduce surface dislodgeability and leachability of the preservative chemicals. These data are being considered as part of the CCA re-evaluation. The environmental risk of CCA-treated wood coming into contact with freshwater and marine environments (including wetlands) is greater than in terrestrial environments and possible restrictions on aquatic use are currently being assessed.
Other Sources of Information
 Canadian CCA Consumer Awarness Program
Environment Canada and Health Canada have cooperated with the wood treatment industry to develop a comprehensive labelling and bilingual public information/education program which includes a Consumer Information Sheet, a toll-free number for consumer information (1-866-679-0957), a Web site (www.ccasafetyinfo.ca) and a program to tag individual pieces of lumber, bundles of lumber and bins and racks with information.
Wood Preservation Sector (Environment Canada)
This website provides information about the Strategic Options Process (SOP) for managing potentially toxic environmental contaminants that are used within the Canadian wood preservation industry. The site also provides an update on the progress that has been achieved by all stakeholders (e.g., wood preservation manufacturing and treatment sector, federal and provincial governments, public interest groups and academia) involved in implementing the recommendations developed from the SOP.
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