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Arsenic Concentration in Air

Air monitoring work by GNS Science has found that atmospheric concentrations of arsenic, a known carcinogen, are above national and international guidelines in a number of New Zealand urban centres.

Studies by GNS Science air particulate researchers suggest that sufficient quantities of timber treated with copper-chromearsenic are being burnt to potentially cause acute or chronic illness in sections of the population. The highest average concentrations of arsenic detected so far were at Wainuiomata in Lower Hutt, Henderson in Auckland and Hastings. Other centres showing elevated levels for briefer periods were at Nelson, Masterton, and other Auckland locations.

Most of the arsenic data was obtained from multivariate PM10 source apportionment studies using ion beam analysis (IBA) to determine elemental concentrations. Councils commissioned GNS Science air particulate research team for the analysis and interpretation reports.
“These findings show that air in New Zealand urban centres is not as clean as we would like to think,” said study leader Perry Davy of GNS Science, “In fact some of the winter measurements are more like the air we expect to encounter in polluted overseas cities.”

The main source of the elevated levels is the burning of treated timber in domestic fires and, consequently, the highest atmospheric levels are occurring in winter. In some cases, atmospheric concentrations have reached twice the upper guideline for human health. The most likely source of the treated timber is off-cuts from renovations and demolitions. The peaks don’t always correspond with the coldest weather, suggesting some of the burning is opportunistic. A further issue was the disposal of domestic fire ash that contained residual arsenic, copper and chromium. When ash is placed on gardens, it represents an additional exposure pathway through the consumption of vegetables grown in contaminated soils.

Councils are responsible for the management of air quality and most councils ban the burning of CCA-treated timber. Several councils have embarked on enforcement and community education programmes, but these results show there is more work to do in this area. Dr Davy said his team hoped to continue the analysis to show long-term trends, particularly the impact of education and enforcement programmes designed to reduce air pollution.

Figure: Arsenic concentrations in Nelson, NZ

Figure: Arsenic concentrations at the St. Vincent Street site, Nelson, New Zealand

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Figure: Arsenic concentrations at the St. Vincent Street site, Nelson, New Zealand