Air quality: Many NZ towns exceed WHO guideline for key pollutant

Key air quality thresholds continue to be breached across New Zealand, a fresh snapshot shows, despite the picture having gradually improved over the last two decades. Photo / Warren Buckland

Key air quality thresholds continue to be breached across New Zealand, a fresh snapshot shows, despite the picture having gradually improved over the last two decades.

Data just published by the collaborative project Land, Air, Water Aotearoa (Lawa) found 18 sites around the country failed national standards for one human-made pollutant last year – while just five of 32 met new international guidelines for another.

While air quality is considered good in most places at most times of the year, pollution rates often spike over the colder months – especially when weather conditions and local landscapes enable smoke to build up over our towns and cities.

Burning treated wood or coal for home heating was especially known to raise levels of harmful particulate matter, or PM.

When breathed in, particles less than 10 micrometres in diameter (PM10) could deposit in the upper airways and cause irritation, while even smaller ones (PM2.5) could lodge deep in lungs and reach the bloodstream.

The data released today showed that 18 out of 60 monitored sites didn’t meet the New Zealand National Environmental Standard for daily average PM10 concentrations in 2022.

And of 32 sites monitored for levels of PM2.5, just five met daily and annual average non-regulatory guidelines recently set by the World Health Organisation (WHO).

The towns where most of those PM10 and PM2.5 breaches occurred last year were Arrowtown, Waimate, Timaru, Geraldine, Ashburton, Christchurch, Kaiapoi, Rangiora, Blenheim, Richmond, Nelson, Masterton, Taihape, Hastings, Taupo, Gisborne, Te Kuiti, Tokoroa, Rotorua and Hamilton.

But overall, monitoring indicated that air pollution had been improving since national standards were introduced in 2005.

“Air quality in New Zealand is generally showing an improving trend where there is sufficient data from regional and unitary council monitoring available,” Waikato Regional Council senior environmental chemist Dr Jonathan Caldwell said.

Of the 44 monitoring sites where a 10-year trend could be determined, two thirds showed improving air quality, around 30 per cent had indetermined trends, and just a fraction showed rates getting worse.

That picture was similarly highlighted in the Government’s latest major stocktake on air quality trends, which also pointed out levels in most places were still above the WHO guidelines.

Today the LAWA Air Quality topic has been updated with fresh insights on New Zealand's air quality.🎉

You'll find info about air quality and trends for places across the country, as well as real-time monitoring data, resources + tips to reduce pollution.https://t.co/I8DF3ptues

— LAWA (@LAWA_nz) June 21, 2023

Cardwell said some people might be surprised to see that air quality in their town appeared comparably worse under those new guidelines.

But, he added, it was important to note these didn’t necessarily mean an increase in pollution.

Rather, the guidelines had been changed to reflect our improved understanding of the health effects from breathing polluted air.

“We now know that even lower levels of pollutants, can have adverse effects on our health and wellbeing and these findings emphasise the need for collective efforts and research to better understand air pollution and ways of further reducing it across the country,” Caldwell said.

For instance, the recent Health and Air Pollution in New Zealand (HAPINZ) study found that nitrogen dioxide (NO2) from motor vehicles accounted for over half the health and social costs associated with air pollution.

Earlier this year, researchers used HAPINZ data to show PM2.5 and NO2 were quietly contributing to thousands of premature deaths here every year.

In 2016 – the most recent year for which suitable population, health, and air quality data was available – the pollutants were linked to an estimated 13,155 hospitalisations and 3317 premature deaths.

University of Auckland aerosol chemist Dr Joel Rindelaub told the Herald at the time how New Zealand lagged other countries in strictly regulating PM2.5 levels – something China had been doing since 2013.

“Over 3300 premature deaths per year are related to air pollution in Aotearoa New Zealand, that’s more than melanoma, diabetes, colon cancer, and road accidents combined,” he said.

“Without a serious effort to address the causes of air pollution... these trends are likely to continue.”

Local councils were currently required to monitor local air quality and remain responsible for improving it when PM10 levels are breached.

While they weren’t mandated to report on PM2.5 levels, many did, and the Ministry for the Environment was considering how best to include the measure in future regulations as part of ongoing resource management reforms.