Marlborough District Council Report on Arsenic
Leaching from treated Vineyard Posts

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 500 mm 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 causal 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 carcinogene in lesser quantities
  and has been found to cause skin cancers, oesophagal 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.