Copper chrome arsenate (CCA) wood preservative was the dominant treatment for structural timber in the UK from the 1950s through to 2004 — used in garden decking, play equipment, fence posts, agricultural buildings, telegraph poles, and structural framing. CCA impregnates wood under high pressure and fixes biocidal compounds deep into the timber matrix to prevent rot and insect damage. The arsenic in CCA is inorganic arsenic — a confirmed Group 1 human carcinogen. Children who played on CCA-treated timber playground equipment were found in US and UK studies to have measurable arsenic on their hands from surface residue, and the US EPA banned CCA for most residential uses in 2003 precisely because of child playground exposure. In the UK, CCA was banned for residential use in 2004 but extensive legacy material remains in gardens and play areas.
Where it's found
Pre-2004 garden decking in UK properties — green-tinged timber is a visual indicator but not definitive (copper-based preservatives give a characteristic green tint). Children's playground equipment and climbing frames constructed before 2004. Garden fence posts and railway sleepers treated before 2004. Allotment raised beds made from old timber. Agricultural outbuildings and farm structures. Telegraph poles (still in use, access should not occur). Structural timber in buildings constructed with CCA-treated components. All legacy CCA timber continues to leach arsenic, chromium, and copper onto its surface for many years after installation.
Routes of exposure
Dermal contact with CCA timber surface is the primary children's exposure route — hands contact the surface, arsenic compounds dissolve in perspiration, and hand-to-mouth ingestion follows. Studies of children playing on CCA playground equipment consistently detect arsenic on their hands above background levels. Adults handling CCA timber during renovation, replacement, or disposal receive dermal and inhalation exposure from cutting, sanding, and sawing (which generates arsenic-containing dust). Burning CCA timber — a significant problem when old garden structures are dismantled and the timber used as firewood — generates highly toxic arsenical smoke.
Health concerns
Inorganic arsenic is a confirmed human carcinogen (IARC Group 1) — it is causally associated with cancers of the skin, lung, bladder, kidney, and liver. Arsenic causes DNA damage through multiple mechanisms including oxidative stress, inhibition of DNA repair, and epigenetic dysregulation. Chromium VI from CCA is also a Group 1 carcinogen. Chronic low-level arsenic exposure from CCA playground equipment has been associated in some studies with elevated urinary arsenic metabolites in children, though the health implications of these measured exposures remain debated. The most acute hazard is cutting or burning CCA timber without respiratory protection, which generates concentrated arsenical aerosol.
Evidence
Inorganic arsenic carcinogenicity is established (IARC Group 1). CCA timber leaching arsenic and causing detectable hand arsenic in children playing on treated equipment is documented in peer-reviewed studies. The US EPA's 2003 ban on residential CCA use was explicitly based on children's arsenic exposure from playground equipment. UK regulatory restriction followed in 2004. The health consequences for children who played on CCA equipment before these bans are a matter of ongoing epidemiological interest but are difficult to quantify given the long latency of arsenic-related cancers.
Who's most at risk
Young children who play on or near pre-2004 CCA-treated timber structures — their hand-to-mouth behaviour and time-on-surface maximise ingestion exposure. Adults who cut, sand, or burn CCA timber without appropriate protection. People who renovate old garden decking or demolish CCA-treated garden structures. Anyone who grows food in raised beds made from old CCA-treated timber.
Regulatory status
RegulationCCA was banned for residential use under EU Biocidal Products Directive (2003) and UK equivalent, implemented from 2004. The ban applies to new treatment; existing legacy material is not required to be removed. Burning CCA timber is illegal under waste burning regulations in the UK. Alternative preservatives (ACQ — alkaline copper quaternary; copper azole; boron compounds) are used for new timber. Building regulations do not specifically require declaration of CCA in existing structures. Disposal of CCA timber requires treatment as hazardous waste at licensed facilities.
How to reduce your exposure
Replace CCA-treated playground equipment with equipment made from alternative-treated or naturally durable timber (larch, oak, sweet chestnut). Never burn CCA timber — the only compliant disposal method is licensed hazardous waste facility. Do not grow edible vegetables in raised beds made from old CCA-treated timber — arsenic leaches into surrounding soil and is taken up by root vegetables. If CCA decking or structures must be maintained rather than replaced immediately, seal the surface with a non-penetrating paint or stain to reduce surface residue transfer. Wash children's hands after playing on or near any pre-2004 timber structures.
The nutrition connection
The carcinogenic mechanism of inorganic arsenic involves oxidative DNA damage, making antioxidant nutrition relevant. Selenium is particularly important: selenoproteins including glutathione peroxidase and thioredoxin reductase protect against arsenic-induced oxidative stress, and selenium and arsenic have competing metabolic pathways — selenium supplementation reduces arsenic toxicity in animal models. Folate supports arsenic methylation (a detoxification process) and DNA repair. Zinc is required for DNA repair enzymes including poly(ADP-ribose) polymerase. A diet rich in allium vegetables (garlic, onions) provides sulphur compounds that support arsenic methylation and excretion.