Chromated copper arsenate (CCA) is a wood preservative that has been used for timber treatment since the mid-1930s. It is a mix of chromium, copper and arsenic formulated as oxides or salts, and is recognizable for the greenish tint it imparts to timber.
CCA is known by many trade names and is the world’s most widely-used wood preservative. In the past, CCA treated timber was commonly used in decking, playground equipment, fences, retaining walls, jetties and vineyards.
The main concern with CCA-treated timber is that it contains arsenic, which can be ingested (swallowed) or inhaled (when CCA-treated timber is burnt). Over time, small amounts of chemicals may leach from CCA-treated timber, but research has found that the amount of leached arsenic is less than that found in common foods.
The US and Canada jointly decided to restrict the use of CCA-treated timber in non-industrial settings after January 2004. An Australia review in 2005 resulted in the following :
CCA-treated timber should not be used to build children’s play equipment, patios, domestic decking, handrails, new garden furniture, exterior seating or picnic tables.
CCA-treated timber can be used for poles, fencing, landscaping timbers, piling and other structure foundations, residential construction, industrial and commercial construction, rural and farm use, fresh and salt water structures, signage and boat construction.
Existing structures made from CCA-treated timbers do not need to be removed and replaced until they reach the end of their functional life.