Timber with a green-grey hue treated with copper chromium arsenic (CCA) is a common sight in New Zealand. But how many people are aware that it泭, is associated with health risks and is a toxic waste complicating the transition to a circular bioeconomy?
Other countries, including泭, the泭泭and the EU, have stopped or restricted the use of CCA, moved to safer alternatives and established viable end-of-life disposal options.
The ingredients of CCA are the heavy metals copper, chromium and arsenic. They dont decompose and cant be destroyed like organic compounds by incineration.
The heavy metals泭, polluting soil and water. When CCA-treated timber is burned, most arsenic becomes volatile and pollutes the air, while chromium and copper contaminate the ash.
The World Health Organization (WHO) lists arsenic among the top ten chemicals of泭. It is a confirmed carcinogen. Chromium and copper are not without health risks either.
Banned or restricted elsewhere
In the early 2000s, the US Environmental Protection Agency and the timber industry agreed to泭. This was driven by concerns about human exposure to arsenic from playground equipment, decks, picnic tables and other uses.
Most other developed countries followed with similar restrictions. CCA is泭泭as a wood preservative in the EU.
But New Zealands treated-timber market is still dominated by CCA. It is used abundantly in playgrounds and residential buildings with a high risk of human exposure. This is despite Standards New 厙ぴ勛圖having approved泭.
New Zealands Environmental Protection Authority also泭recommends泭building playgrounds from alternative materials, providing consumer information at point of sale and greater dissemination of precautionary health advice. But these recommendations have been ignored in New 厙ぴ勛圖for two decades.
Stakeholders have not adopted the泭泭developed jointly by Standards Australia and Standards New Zealand. The standard contains a consumer safety information sheet, which states CCA-treated timber cannot be used for products in direct contact with foodstuffs, garden furniture, exterior seating, childrens play equipment, patio and domestic decking and handrails.
It also details appropriate disposal and outlines precautions during handling:
avoid sawing
wear dust masks, gloves and eye protection
wash hands and face after working with CCA-treated timber.
Environmental and health risks
New Zealand泭excluded environmental risks泭from its CCA safety assessment. Yet environmental risks were leading reasons to phase out CCA overseas.
There are several domestic examples of environmental pollution by CCA.
泭in the air during winter泭exceeds New Zealands ambient air-quality guidelines. This is caused by inappropriate burning of CCA-treated timber in log fires and burn-offs by the agricultural sector.
Arsenic concentration was泭泭in slow-flowing Marlborough aquifers.
While soil contamination is localised around CCA-treated timber, these hotspots can be frequent.泭, for example, feature 500-600 posts per hectare. Land-use change for urban development will require泭significant remediation.
Improper disposal of ash from log burners in green bins causes泭. Deliberate泭泭has also been uncovered.
In a study of 35 countries, New 厙ぴ勛圖was the only one where arsenic contamination of residential indoor dust泭泭for children.
No safe disposal
CCA is also an obstacle in the泭transition to a circular bioeconomy. Reuse of timber is a well established procedure. It prioritises reuse over thermal utilisation (using it as fuel to harness its energy).
However, there is no viable reuse for CCA-treated timber waste. The problem is even bigger. CCA-treated timber泭cannot be separated from untreated timber泭in demolition waste.
In New Zealand, CCA-treated timber is to be disposed in secure landfills, forcing future generations to manage the toxic CCA泭. Burning in appropriate facilities is the only viable disposal method for CCA-treated timber it is the mandatory disposal option in Germany. However, no sizeable waste incineration plant has been commissioned in New Zealand.
A brief visit to any school, playground, picnic area, domestic garden or DIY shop demonstrates New Zealands comparatively relaxed attitude towards CCA. Government and industry state to never burn CCA-treated timber, but this is not communicated to the public effectively.
Recent advice at my local DIY stores included, yes, its standard for playground equipment and it can be burned or recycled. Preservative-treated wood is frequently sold as firewood. At my last check, three out of the top 50 firewood listings on the auction site TradeMe were泭CCA-treated timber waste.
New Zealands industry-led approach has failed. The first step to tackle the CCA liability is easy, as alternative preservatives are approved. Restricting the use of CCA-treated timber or introducing a泭product stewardship scheme泭will ensure nothing is added to New Zealands CCA legacy.
Ensuring our children do not have to inherit the existing CCA legacy is more difficult. We need to commission a suitable incineration facility.
CCA-treated timber is cheaper than safer alternatives but only if disposal costs are outsourced to future generations.
This article was originally published on泭
Disclosure statement
Clemens Altaner is Science Team Leader of the New 厙ぴ勛圖Dryland Forests Initiative (NZDFI). He has received funding from industry and government for work on naturally durable timber.
