Isn’t arsenic a thing of the past? No, it’s still commonly used and you may find that it’s found in more places than you’d think.
A timber retaining wall such as this one is a common use of Copper Chrome Arsenate treated timber.
Where will i find Arsenic around my home?
The most likely place is in treated pine sleepers. The arsenic is in the preservative treatment for the timber in the form of compounds of Copper, Chromium and Arsenic. The Copper prevents fungal attack, the Arsenic prevents insect (like termite) attack on the timber and the Chromium binds these two to the timber. It certainly is effective in preventing termites and other timber pests, but that’s not the scope of this post.
What does CCA treated timber look like?
CCA treated timber must be labeled as so when being sold prior to use, so you will likely see a label to that effect. Once in situ, the timber has a greenish tinge when newly treated, this will fade over time.
This H4 treated timber is clearly labeled as treated with Copper Chrome Arsenate.
What are the risks?
Should I be worried about using CCA treated timber?
CCA treated timber is hazardous, and as such, in 2005 the Australian Pesticides and Veterinary Medicine Authority advised that timber containing CCA is not to be used for high contact structures such as playground equipment. Additionally on the 1st July 2012, new restrictions were in place which stipulates that CCA treated timbers need to be supplied to, and used by suitably qualified individuals based on the authorisation provided by a relevant state or territory law.
This wording can seem ambiguous and difficult to decipher, however, in simple terms: in our experience, at the time of writing, in NSW, Australia, CCA treated timber is readily and easily purchased from local hardware suppliers with little, if any enquiry or determination of the suitability of the material for such use. As a case in point, a client of ours purchased and built a cubby house for their children with CCA timber on the “window sill” of the cubby house. A high contact area!
A Cubby house Built with CCA treated window sills.
Is it safe for my child to play on CCA Equipment?
According to International studies, children playing on CCA treated timber play equipment contributes between 2–8 per cent of the safe daily acceptable limits set by the World Health Organisation. It also is within the safe daily acceptable limits set by the Australian Department of Health and Ageing.
What can I do to protect myself and my family?
There is much research into the effects of CCA when touched through normal use in timber structures, and the statistics and conclusions vary. However, based on the Western Australian Department of health, there are some minimum precautions that can be taken.
Wash children’s hands after using play equipment.
Put food onto plates and napkins rather than directly on a wooden picnic table.
Additionally, some research suggests there is some benefit in painting timber to limit exposure to arsenic, painting with an oil based paint or stain may reduce the exposure. The coating will need to be applied every 12-18 months.
When it comes to raised garden beds, if you’re using CCA treated timber for your vegetable garden, you may want to line the inside with plastic before adding soil and keep plants away from the edge of the garden bed. Although the preservative is designed to remain locked in the timber there could be some leeching. This will help minimise edibles absorbing preservative compounds from the timber.
This vegetable garden bed could do with some lining to minimise any preservatives from the timber entering the edible plants!