New Zealand's air quality has been described as an "environmental good news story" by Government's environmental watchdog.

Commissioner Jan Wright today released her analysis of the first State of the Environment report to be jointly written by the Government Statistician and the Ministry for the Environment.

Environmental monitoring reports on air, climate, freshwater, oceans and land will become mandatory under a law change later this year, and Dr Wright will be tasked with providing independent commentary on each report.

In her first piece of commentary on the health of New Zealand's air, she wrote: "Overall, air quality in New Zealand is a good news story."

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This could be expected in a windy, maritime country with a small population, she said. But market trends and changes by central and local government had also contributed to cleaner air across the country.

Airborne particles created by home fires or car emissions and associated with health problems such as respiratory illness had reduced by 75 per cent in Auckland in the last 50 years, and similar progress had been made in other towns and cities.

This improvement was mostly credited to the shift from heating homes with coal or wood to heating homes with electricity or more efficient burners.

Other important changes were stricter emissions standards for new vehicles, the retrofitting of insulation in homes, and the greater availability of natural gas.

Dr Wright said she worried more about an environmental issue if its effects built up over time and its impacts were not only increasing but accelerating.

"When I apply these criteria to air pollution, it does not look like an important issue," she said.

But she noted that the inhalation of air-borne particles had real health impacts and remained a serious public health issue.

Some towns, in particular in the South Island, exceeded the World Health Organisation (WHO) guidelines for long-term exposure to PM10 (very small airborne particles, 10 micrometres or less in diameter) Timaru, Invercargill, Alexandra, Ashburton, and Gore and others had higher concentrations of particulate matter when the wind died down and temperature inversions trapped the particles closer to the ground.

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Dr Wright made several recommendations for monitoring air quality. She wanted the State of the Environment reports to make clearer conclusions on environmental indicators and to clearly identify which locations were worst-affected.

The commissioner also wanted the national standard for air quality to be reviewed.
At present, councils set limits on air pollution based on short-term exposure to PM10 - contrary to WHO guidelines which state that the most important factor to measure is long-term exposure to ultra-fine particles known as PM2.5.