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This report prepared for the Council by HortResearch has raised a number of concerns regarding the use of treated posts, (Copper, Chromium, Arsenic treatment), as trellising support. The report was commissioned by the Council following the detection of abnormal levels of arsenic in groundwater in some areas of Marlborough.
In summary the findings are that:
- Overseas studies have found that over time arsenic from treated posts leaches into the soil.
- Arsenic leachate has been found leaching from posts in Marlborough. In some cases it was found up to 500mm from the posts and further beneath the post.
- Some 25% of the tests exceeded health guideline levels.
- So far, evidence has yet to determine the amount of leachate as a casual agent in death. The Environmental Protection Agency of the United States Government has been moved to ban all treated timber in house construction, playgrounds etc.
- Arsenic apart from being a deadly poison is also a carcinogen in lesser quantities and has been found to cause skin cancers, oesophageal cancer and lung cancer.
- With the rise and fall of the water table in the Marlborough region and the fact that posts are dipping in and out of the groundwater it is reasonable to assume leaching of arsenic into that water.
The issue of CCA treatment and the resultant leaching could be eliminated by the use of posts made of concrete, steel or untreated woods. Or treated posts could be coated to inhibit or slow leaching.
A full copy of the report can be obtained from the Marlborough
District Council. The complete report contains a summary
of findings, methodology and the scientific data.
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