Kiwi homes are being wrapped with plywood containing an arsenic treatment banned in several overseas countries because of toxicity concerns. Sources: Stuff.co.nz, Fairfax NZ News
Bracing plywood treated with the preservative copper chromium arsenic (CCA) is increasingly being used for residential repairs and rebuilds in Canterbury.
Both arsenic and chromium compounds pose a potential health hazard in certain conditions. Public health concerns about CCA arose 10 years ago when arsenic was found to leach from the treated timber, often used for decks, framing and playground equipment.
Plywood bracing products have appeared on the market since then becoming more popular after leaky homes concerns and are now in common use.
CAA is either banned or has restrictions placed upon its use in the United States, Canada, and several European Union countries including France, Spain, Italy, Germany the United Kingdom and Ireland. Japan, Indonesia, Vietnam and Australia have placed restrictions on its use.
CCA has pesticide and anti-fungal properties and New Zealand is one of the world’s biggest users of CCA treated timber products. The preservative process allows wider use of pinus radiata, which is a perishable fast-growing softwood not naturally resistant to insects and fungi.
Dr Meriel Watts, who has a PhD in pesticide risk assessment and policy, said CCA-treated timber products posed an “unacceptable risk for public health”, particularly for young children.
Watts, scientist co-ordinator for Pesticide Action Network NZ, said arsenic from the preservative could leach into soils or water, while offcuts were often burned through ignorance, creating a “serious health risk”.
In Australia, dangerous levels of toxins have been measured when homes containing CCA burned in bushfires. Kevin Hing, director of the New Zealand Timber Preservative Council, which represents the timber treatment industry, said CCA had been used for years with no recorded cases of illness or death in New Zealand.
Touching the treated timber led to low levels of arsenic exposure. He warned the treated timber should never be burned, must be disposed of in hazardous waste landfills, and precautions should be taken when cutting it.
New Zealand’s official hazard protection agency, the Environmental Protection Authority, said this week it keeps CCA “under review”, but cannot ban the preservative without reassessing it. It also cannot control how the substance is used.
A report by the agency in 2003 concluded that despite its known toxicity, there was insufficient evidence for a ban. However, the report noted large gaps in knowledge and evidence about health risks. It urged schools to avoid or at least seal any timber treated with CCA, and advised workers using it to wear masks, gloves, and protective clothing.
One senior figure in the Canterbury construction industry, speaking on condition of anonymity, said the sealant properties of some forms of the plywood created dangerously unhealthy homes, trapping toxins and moisture inside.
“[Timber] workers have to handle it with gloves and full body suits, and we are wrapping our houses with it,” he said. “Why on earth are we using these products?”
Plywoods made in New Zealand that can contain CCA include Ecoply and Shadowclad, both made by Carter Holt Harvey, and J-Ply, made by Juken NZ.
Residential uses include wall lining, external cladding, and moisture sealing.
Some plywood products treated with alternative preservative methods are available in New Zealand but they are more expensive.
In 2003 a report from Australia’s University of Wollongong concluded: “…it would be prudent public health policy to reduce human exposure to arsenic from all sources wherever feasible.”
Building and Construction Minister Maurice Williamson’s office referred questions to the Ministry of Business, Innovation and Employment, which said the 2003 review had considered existing legal limits for the amount of CCA in timber were safe.
The ministry was not aware anything has changed since that assessment, and noted that there were alternative timber treatments in New Zealand without chromium or arsenic. When told of the issue, Labour Party building and construction spokesman Shane Jones expressed concern and promised to raise the matter with Building and Housing Minister Maurice Williamson.
House builders around Christchurch seem to use few precautions working with treated timber.
“We use it all day. I know about the treatment but I don’t take many precautions,” said foreman James Lewis, busy building units on a Wigram site.
Workers on the site are using more than one timber product treated with CCA. Dust from skillsaws floats around them and out into the neighbourhood, which is full of family homes.
The product wrapping contains health recommendations but the guys say the precautions are impractical onsite. Gloves get hot and sweaty and make it hard to pick things up safely, and constant hand washing when they use the products all day slows things down.
Builder Dan Robinson on the same site said he was worried about all the timber products he knew contained chemicals that if handled incorrectly could potentially be a health hazard.
He thought they were not a good idea in houses in case of fire but was surprised to hear some contained arsenic. “I thought it [the timber] was eco-friendly. They bring up so much information about safety on the building site, but not about this.”
