CCA is a mixture of copper, chromium and arsenic that is injected into soft woods to prevent fungal decay and termites. Until recently wood treated with arsenic was commonly used for decking, fencing, poles and most outdoor uses of timber.
Wood dust from any timber including CCA treated timber may cause skin irritation and breathing difficulties. It may aggravate asthma, eye infections or affect wearing of contact lenses.
Exposure to any air borne wood dust over long periods of time has been associated with the development of nasal cancer. Arsenic and wood dust are classified by the International Agency for Research on Cancer (IARC) as confirmed human carcinogens.
CCA can be recognised by the green tinge it leaves on the wood but it is not always easy to detect once it's weathered or painted.
CCA leaches from timber due to weather and rain, and if the timber is used for domestic purposes its CCA constituents can contaminate the skin. Those working with It (cutting, sanding) can breathe the CCA constituents with wood dust, Increasing the hazard and cancer risk. In Australia, one authority (Australian Pesticides & Vetinerary Medicines Association) has recommended that CCA treated timber not be permitted for use in garden furniture, picnic tables, domestic decking/patio, handrails, exterior seating and children's play equipment, though another authority (enHealth Council) has disagreed with this recommendation.
If CCA timber is used domestically outdoors where it is in contact with skin, or if dust is inhaled through working with the timber, over time the exposure rate is greater and the risks of developing health effects are increased.
Alternative wood preservatives are available that don't contain CCA. LOSP (Light Organic Solvent Preservative) are solvents and preservatives, such as linseed and kerosene, which can be used instead of CCA. If you have CCA timber already in place you can use a sealant or paint to prevent picking up the components from skin contact with CCA timber, but this coating then needs to be maintained regularly like other coated timbers around the house.
