‘Burning of offcuts poisoning our air’

Burning offcuts of treated and painted timber is releasing harmful substances into the air in many New Zealand cities.

Research by GNS Sciences has found levels of substances like arsenic and lead reached up to three times the guideline for human health in winter in some inner-city areas.

The findings were important, study leader Perry Davy said, in light of recently released findings from the Otago Study, which showed lead exposure in childhood could reduce a person’s IQ and social standing later in life.

Davy said the tendency for toxin concentrations to jump during colder times suggested the burning of construction offcuts was the cause.

Wainuiomata in Lower Hutt, Christchurch and Henderson, in Auckland, had some of the highest average concentrations of lead and arsenic, while Hastings also had high concentrations.

The Ministry of Health links low lead levels in blood to impairment of children’s brain development and performance at school, while high levels can cause symptoms in any age group, including sleeping problems, diarrhoea, nausea and loss of appetite.

Acute exposure to arsenic could cause stomach pains, vomiting and diarrhoea, and extreme tiredness, while long-term exposure could cause problems ranging from damage to the heart, liver, and kidneys to several forms of cancer.

While the toxins had the potential to harm the general population, Davy said the effect could be far worse for households that were burning them.

‘‘We have no idea what the concentration might be inside the home or in the neighbourhood of someone burning this stuff.’’

This could pose a particular risk to children, whose smaller size and different metabolism made them more susceptible to the neurotoxins.

When the ash containing residual toxins was placed on gardens, Davy said it represented an added danger to those who might breath it in or eat vegetables grown in it.

Lead was removed from petrol more than 20 years ago, but Davy said many Kiwis might not realise lead and other harmful substances were still present in construction timber.

Davy’s advise was to avoid burning any timber offcuts, because it was difficult to tell if it had been treated.

The study ran for 15 years, Davy said, and the concentrations of substances had been largely consistent.

‘‘These studies show that air in New Zealand urban centres is not as clean as we would like to think.’’

Davy said councils were responsible for managing air quality and most had banned the burning of timber treated with arsenic compounds.

‘‘There is clearly more work to do in this area,’’ Davy said.