Fires no place for treated wood

All right folks, it's time to 'fess up. No names mentioned, but you know who you are.

Those of you burning treated timber in your home fires have been spewing toxic fumes into Nelson's air. And Nelson City and Tasman District councils want you to stop.

In case you haven't heard, CCA-treated timber contains chrome, copper and arsenic. When the timber is burnt, most of the arsenic goes up the chimney and into the atmosphere attached to minute particles.

The rest of the arsenic is left in the ash, along with the residual chrome and copper, and is, according to Institute of Geological and Nuclear Science Wellington-based scientist Perry Davy, "not what you would want to be putting on your garden".

Dr Davy's findings of spikes in atmospheric inorganic arsenic during the winter of 2009 at Tahunanui monitoring sites were drawn from air quality monitoring work commissioned by the Nelson City Council.

The Tahunanui monitoring is part of the council's programme to understand, manage and improve air quality in the region. To meet new national standards in 2008, the council introduced its air quality plan, aimed at making a 70 per cent reduction in superfine particulate emissions, 80 per cent of which was identified as originating from domestic fires and wood burners.

Suspecting people were burning treated timber on their fires, Dr Davy looked at arsenic levels in three locations around the country already being monitored by GNS for air quality – Auckland, Wainuiomata and Tahunanui – and found dramatic increases in levels during winter in all three, consistent with the main fire-burning period.

In the Tahunanui case, he found levels of arsenic around 40 times greater in winter (spiking many times from May to September during 2009) than during January of the same year when levels were almost nothing.

Dr Davy's findings were presented to a national air quality working group in November last year and are being published later this year.

While average arsenic concentrations found at Tahunanui were below that of the Ministry for the Environment's ambient air quality guidelines, the spikes of winter 2009 went well above it many times during that period. As ministry spokesman Peter Fitzjohn explains: "The ministry's ambient air quality guidelines provide the minimum requirements outdoor air quality should meet in order to protect human health and the environment." They are not legal requirements, he adds.

Dr Davy highlighted the "potential for acute effects given the winter peaks" in arsenic levels, but also pointed out the potential for chronic effects "due to repeated winter-time exposures".

Among disturbing effects of arsenic on human health listed on the Environment Ministry website, it also notes "human inhalation studies have reported that inorganic arsenic exposure is strongly associated with lung cancer".

While CCA-treated timber is a prohibited fuel under the Nelson air quality plan, it clearly hasn't stopped people from burning it, the council's monitoring co-ordinator, Paul Sheldon, says.

"At any building site you wind up with a mountain of this stuff and you can either pay to dispose of it or burn it. Clearly, some people are taking the latter option."

While it makes it virtually impossible to police, the option left to reduce the arsenic emissions is for councils to educate people to stop burning treated timber, he adds.

Although some building sites offer roadside bins of free offcuts, Tasman District Council environmental education officer Rob Francis said when their staff checked such bins, most did not have much in the way of CCA-treated timber in them. Which tends to point the finger at the homeowner doing a renovation, or people who have access to treated offcuts from building sites.

But treated timber is not the only cause of particulate pollution. The city council has also targeted older burners it considers are inefficient because of their design; and people burning wet wood. The programme to require the removal and replacement of older burners across the most pollution-prone parts of the city concludes next January.

Meanwhile, the council's plan also bans burning wet wood (with more than 25 per cent moisture content), but policing such a policy is difficult, concedes Nelson City Council's team leader of environmental services, Richard Frizzell. Both Nelson City and Tasman District councils have started an educational "good wood" scheme, listing suppliers who follow council requirements and promote quality firewood.

Paul MacLennan, of A Miller and Sons, is a seasoned supplier in the good wood scheme and says changing the burning rules and emission limits changed the whole dynamics of his business.

"A lot of people are buying their wood earlier. Sales in December and January are two times more than six years ago."

While he readily admits he was less than happy when the new regulations were introduced and the potential for loss of business, he now concedes it has spread his supply season and helped hugely with cashflow.

His only challenge now is meeting demand, given wider timber industry changes which have seen douglas fir double in price on the export market in the last year. "It means we just have to look harder [for good firewood]."

What most people don't realise though, he adds, is that the new, low-emission wood burners need not only dry, seasoned wood to burn well, but also soft (conifer) wood, not hard woods, to burn cleanly and efficiently.

And, rather than blaming wood quality on emissions, Mr MacLennan says it is a fire management one.

Mr Frizzell agrees it is important to get people to manage their burners correctly and reducing operator error is part of the overall air quality education strategy.

While there has been some opposition to the phase-out of old fires, he says faced with the huge task the council had to reduce emissions – most of which came from domestic fires – there were few options. "If we can control the burners going in then we can concentrate on getting the wood right." Hence the good wood scheme.

According to air quality monitoring in the city, it looks like the plan is working.

Mr Frizzell says last year was Nelson's best yet for staying within the national allowable air particulate limits. "Last year we had seven exceedences. Before that, our worst level ever was 81 times [in a year]."

He is optimistic the air quality will continue to improve as all old burners are phased out by January next year and people will come to appreciate the improvement.

Watch this space.