Thanks to Matt for an interesting cross post…
CCA-treated timber is everywhere: parks, decks, jetties even in ours homes, but how safe is it when it comes to food, drink and our children’s safety? CCA-treated timber is timber preserved with Copper Chrome Arsenate (CCA) or Chromated Copper Arsenate, as it is known in some countries, like South Africa. The copper (23-25%) and arsenic (30-37%) in CCA act as fungicides and insecticides, while the chromium (38-45%) fixes the chemicals into the wood (APVMA, 2003; Greaves 2003). The chemical mixture is injected into the wood under pressure so that the wood is saturated with the chemicals.
Of greatest concern is the potential seepage of arsenic, a known human carcinogen, onto the surfaces of CCA-treated timber from where it can be dislodged onto
hands and washed off into nearby soil or surrounding water. However, there is a lack of health studies on the combined health impact of copper, chromium and arsenic.
Extensive tests have been done by the Department of Agriculture SA, United States Department of Agriculture and the Environmental Protection Agency, all of which have found it to be ‘food safe’ in the use of raised vegetable gardens. An 8 year study showed a nominal increase in arsenic being leeched into the soil, most of which were stored in root vegetables like carrots and beetroots, but in parts that are normally discarded. The Federal Drugs Administration however disagrees and says it is both unsafe for storing/growing food and or water. In the USA it has been classed as a ‘restricted risk’ product and is banned from being sold to consumers. In countries like Australia, Europe, the USA and Canada have banned its use in recreational settings, such as parks, because of the risk it poses to children.
In 2001 a study done by Sharp and Walker shared this:
‘A 4-6 year old child’s daily exposure to arsenic has been found to be 5 micrograms/l in food, 23 ug/L in water, 25 ug/L from playing on CCA-treated wood and up to 480 ug/L from playing on CCA treated playground equipment’ (p.1). Children could exceed the legally-acceptable lifetime cancer risk in 2 weeks by playing on a treated play set.
Obviously this, along with other factors have forced the hand of these first world countries, but it is still sold here in SA to consumers and contractors alike.
Let me pepper this by saying that organic arsenic is all around us, in our water, our soil etc, so we are exposed daily to these risks, but as shown above the risk CCA timber poses to added exposure is a problem.
Lining the timber or coating it does reduce the risk of leeching further, but only for a year or 2, then a new coat of sealant needs to be applied.
Why do I even raise the issue? Well as some of you know I’m looking to start a business supplying portable food gardens to end users and am at a quandary as to how to go about it and I’m trying to remain impartial and objective.
Currently the 2 largest suppliers of such products here in Cape Town use unlined CCA treated timber in their ‘organic’ food gardens (which is a misnomer as certified organic farms are prohibited from using ANY CCA timber).
Again I see the benefits in that they are long lasting and require no maintenance, but the risk, however slight, remains.
The alternative? Using untreated timber and coating it will an environmentally friendly sealant, or not at all. The downside is that if treated it will need periodic maintenance, if not the wood will eventually rot and need to be replaced, which is a costly exercise, yet environmentally friendly.
So armed with that information, as the general public, what are your feelings? If you were to purchase a said food garden would you be willing to pay 20% more to have sealed or untreated timber planter and deal with the annual maintenance with no risk of contamination or would you be happy to use the CCA timber knowing that the risk is low, but still a risk?
Understand that my focus is solely on food garden usage, not flowers, only edible goods. Pressure-treated wood does last longer as shared than untreated wood, so using it might mean fewer trees would be cut in places where contact with food/water is limited.
Click here or further in-depth reading/study in both the process and undertaken studies visit
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