Copper chrome arsenic (CCA) treated timber

Copper chrome arsenate (CCA) treated timber is wood that has been treated with a preservative containing copper, chromium and arsenic. The treatment prolongs the life of the wood, which is why CCA-treated timber has commonly been used in decking, playground equipment, fences, retaining walls, jetties and similar outdoor structures.

The CCA process was first developed in 1933 and is used worldwide. Concerns have since been raised about the potential health risks of CCA-treated timber.

How the preservation process works#

Copper and arsenic in the preservative protect the wood from insect and fungal attack. Chromium (chrome) “locks” the copper and arsenic into the timber and reduces the risk of the chemicals leaching out. The process gives the treated wood a green tint.

Arsenic#

The main concern with CCA-treated timber is that it contains arsenic, which can be ingested (swallowed) or inhaled (when the timber is burnt). Over time, small amounts of the chemicals may leach from the timber, but research has found that the amount of leached arsenic is less than that found in common foods.

Because people are exposed to naturally occurring arsenic in soil, water and food, the human body can tolerate small amounts of arsenic.

Concerns and recommendations#

Although the chemicals are fixed within the dry wood, concerns have been expressed internationally about the potential for harm, as small amounts of arsenic can leach from the surface of the timber. Regulators in a number of countries have decided to restrict the use of CCA-treated timber in non-industrial settings, and safety reviews have been carried out internationally.

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.

It can be used for poles, fencing, landscaping timbers, piling and other structural 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 timber do not need to be removed and replaced until they reach the end of their functional life. These recommendations are precautionary, as there is no evidence that CCA-treated timber is harmful when handled or used properly.

How to reduce risk in your home workshop#

Limit your possible exposure to the chemicals as a precaution. When using CCA-treated timber at home, you should:

• select the correct timber for the job, as timbers are treated to different levels according to their intended end use
• observe any warning labels on the timber
• cover existing skin injuries such as cuts, wounds or abrasions before you work with it
• wear a dust mask labelled either P1 or P2 to avoid inhaling sawdust (P2 masks are sometimes called N95 masks)
• wear eye goggles, gloves and appropriate clothing to prevent splinters
• keep food and drinks away from sawdust or treated wood surfaces
• wash your hands and face after working with the wood, and before eating, drinking or any other hand-to-mouth activity
• avoid sawing or sanding the wood in confined spaces, and work outdoors whenever possible
• clean sawdust from personal protective equipment (PPE) before using it again
• clean your workshop or garage thoroughly and don’t leave sawdust lying about
• reseal cut surfaces with a timber preservative
• use stainless steel or hot-dip galvanised plates, bolts and nails

Playground equipment#

It has been suggested that children could ingest tiny amounts of arsenic from their hands after playing on CCA-treated timber play equipment, or from swallowing the soil surrounding it. However, there is insufficient evidence to demonstrate that CCA-treated timber poses a health risk. The timber has been in use for many years and no cases of adverse health effects have been reported in children playing on or near such equipment.

Precautions to reduce children’s exposure include:

• don’t allow food to come into contact with CCA-treated timber play equipment
• make sure children wash their hands after playing outside and before eating or drinking

There is no need to remove existing CCA-treated timber play equipment from your backyard. It is unknown whether painting or sealing the equipment is helpful. If you are planning to build play equipment, ask staff at your local hardware store about other treated timber products.

CCA-treated timber and fire#

Do not burn CCA-treated timber in fireplaces, barbecues, wood stoves or any wood fire. If treated timber is burnt, for example in a wildfire, the ash can contain up to 10 per cent (by weight) of arsenic, chromium and copper. Swallowing only a few grams of this ash can be harmful.

Symptoms can include nausea, vomiting, diarrhoea and a “pins and needles” feeling in the skin. Keep children and pets away from CCA-treated ash until it is removed, and see a doctor if you or anyone in your family shows signs of having eaten it.

Ash from CCA-treated timber can be double-bagged, sealed and taken directly to landfill. When removing it, wear protective gloves, disposable overalls and a P1 or P2 face mask (P2 masks are sometimes called N95 masks) to minimise exposure to dust. Do not bury CCA-treated timber ash, and check with your local waste authority for advice or requirements.

Reducing risk and disposal#

Suggestions to reduce risk include:

• wash your work clothes separately after cutting or sanding CCA-treated timber
• don’t use CCA-treated timber for kitchen cutting boards, countertops or food containers
• never burn CCA-treated timber in fireplaces, wood stoves or any wood fire
• don’t use CCA-treated timber sawdust in mulch, compost or animal feed
• don’t leave CCA-treated timber where others may take it for firewood, for example by leaving it out at the roadside

Small amounts of CCA-treated timber offcuts can be placed in your regular rubbish bin. Timber from larger household building or demolition jobs can be disposed of at approved landfill sites. Contact your local waste authority for further information.

Alternative timber treatments#

Be guided by the relevant timber associations, but generally speaking it may not be advisable to use CCA-treated timber for animal cages if the animal likes to chew on wood, such as bird cages. Don’t use CCA-treated timber to build fish ponds.

Arsenic-free alternative timber treatment products are available and registered for use. These control a similar range of pests to CCA treatments. Ask your local hardware store about alternatives suitable for your intended project.

Key points#

• CCA treatment prolongs the life of the wood.
• Concerns have been raised about the potential health risks of CCA-treated timber.
• Chromium (chrome) “locks” the copper and arsenic into the timber and reduces the risk of the chemicals leaching out.
• Wear eye goggles, gloves and appropriate clothing to prevent splinters.
• There is insufficient evidence to demonstrate that CCA-treated timber poses a health risk.

Where to get help#