In 2003, the United States Environmental Protection Agency and the lumber industry agreed to discontinue the use of CCA-treated wood in most residential construction.
As a result of this decision, CCA-treated wood can no longer be used to construct residential structures such as playground equipment, decks, picnic tables, landscaping features, fences, patios, and walkways.
Nevertheless, CCA remains a popular and economical option to make perishable timbers, such as plantation-grown pine, viable for applications like poles, piling, retaining structures, etc.
The composition of CCA products is usually described in terms of the mass percentages of chromium trioxide or "chromic acid" CrO3, arsenic pentoxide As2O5, and copper(II) oxide CuO.
[5] However it has a long list of negative health effects, especially in inorganic form, by contact or by ingestion, and was designated a human carcinogen by the U.S. Environmental Protection Agency (EPA) in 1986 (even though its actual risk remains unclear).
[3] Regulatory action was motivated in the 1990s by studies suggesting that CCA could pose a risk to children in playgrounds built with CCA-treated timber.
[7][8][9] Machining (sawing, sanding, drilling) CCA-treated wood also exposes construction workers and amateur carpenters to chronic and acute health risks via inhalation.
[3] CCA treated wood has relatively low toxicity, and animals would need to ingest unlikely amounts (28 g daily for a month, for an adult horse) in order to become poisoned.
[12] The amount and rate of arsenic leaching varies considerably depending on numerous factors, such as local climate, acidity of rain and soil, age of the wood product, and how much CCA was applied.
Sawdust and other residues left over by construction may be a much more significant source of arsenic pollution to soil and environment than leaching from the final timber structure.
[4] Acute and chronic arsenicism have been reported to result from inhalation of smoke from burning of CCA-treated wood, such as in the use of scrap timber as fuel for industrial or domestic fires.