KEY POINTS:
Despite the clean, green image, scientists say the air quality of New Zealand cities leaves much to be desired.
Winter's onset is expected to worsen air quality considerably, with log burners becoming bigger culprits than car exhaust emissions.
"There are places in our country, even small towns, where we have horrendous air pollution problems," said Dr Andreas Markwitz, team leader of GNS Science's air pollution study programme.
Analysis by the National Isotope Centre has revealed worrying levels of fine particulates - the noxious by-products of inefficient fuel burning that can aggravate or cause respiratory problems.
Ministry for the Environment standards stipulate that fine particulate emissions should not exceed 50 micrograms per cubic metre of air over a 24-hour period, in line with World Health Organisation (WHO) standards. Councils are allowed to breach the threshold once a year.
Last year, Christchurch breached the threshold 32 times between May and September, with the highest reading 183 micrograms - nearly four times the limit. The number of breaches has, however, been steadily reducing over the past five years.
Wellington, meanwhile, recorded only three breaches last year, all in Masterton. Fine particulate matter was the only pollutant that approached limits set in the national standard.
Auckland recorded six breaches last year - five over winter.
Councils have until 2013 before harsher penalties come into force.
Another WHO standard stipulates that fine particulate emissions should not exceed an average of 20 micrograms per cubic metre of air a year.
In Auckland, the figure varied between 18 and 23 micrograms between monitoring sites in 2005.
Dr Markwitz said that in less populated areas, one-off breaches were recorded between three and five times a year.
At a conference on air pollution in Manila recently, the doctor was surprised that particulate levels in New Zealand cities were worse than in their Asian counterparts.
Bandung in Indonesia (population 2.5 million) had around 10 to 30 per cent better air quality.
"While the air in Manila might be a little worse, we in Auckland should have super cleaner air.
"What you can see across Asia, except in a couple of countries, is a strong effort to improve air quality. So even in Manila, in five years' time, smog is probably not going to be as big an issue as in Auckland.
"In principle, we're still on an increasing slope. We're not on a downward trend."
Auckland Regional Council's manager of air quality Kevin Mahon says domestic fires contribute 64 per cent of fine particulate emissions in winter, while the region's 750,000 vehicles contribute 27 per cent.
"While it's not the biggest contributor across the whole year - motor vehicles are - it is a large secondary source."
Mr Mahon said the WHO's review of medical studies had concluded that the long-term effect of exposure to high levels of fine particulates was 10 to 15 times worse than one-off exposures.
"For a city that is relatively small, in international terms, we are more polluted than we should be,or than we need to be."
Particles less than 2.5 micrometres can travel into the bloodstream without being filtered by the lungs.
"The big impact actually is the reduced activity days. For those people with asthma and bronchitis, or respiratory illness, they're the ones that get the initial impacts, and they're the ones who find that they're not well enough to go to school or to work."
Mr Mahon said that in Auckland, a few thousand people lost a combined estimate of 750,000 days a year from being unwell from air pollution.
He said data from the GNS programme and the regional council's own work would help to improve air quality.
