Wellington air quality improves, but significant issues remain - report

Windy Wellington's air quality should be among the best in the world, but it has been getting worse, a new report has found.

The increased use of diesel buses in the city centre have been cited as the cause in the report.

Meanwhile, Wairarapa woodburners are causing many more times the number of acceptable high-polluting days.

The report estimates it could take decades for Masterton and Carterton to reach clean air goals.

'I think about I think about air quality all the time' - air quality

Greater Wellington Regional Council's (GWRC) Environment and Climate Committee has revealed that Wellington's air quality has improved considerably since monitoring began in 2016, but that significant issues remained.

The report stated that the region "should have some of the best urban air quality in the world" as it was bordered on three sides by coastlines exposed by constant sea breezes and strong westerlies.

It found that air pollution was of particular concern in the Golden Mile - a busy transport and retail corridor in the capital - where improvements were being reversed.

The amount of black carbon in the air on Manners Street has risen by 15 percent between 2023 and 2025.

The report cited an increase in diesel buses along the route, following higher passenger demand, as the cause.

Businesses along the Golden Mile were exposed every day.

"I think about I think about air quality all the time," Unity Books manager Susanna Andrew said.

"I bike in every morning, so I do fill my lungs up with some good air, and it's an amazing city to bike in around that waterfront.

"But when I get here into Lambton Quay [...] it's a heavy dollop of diesel fume when there's a lot of buses coming in."

Several out-of-towners walking down the Golden Mile told RNZ they could noticeably feel the air quality in the city was not as good as outside of it.

'The only safe level from air pollution is actually no air pollution'

While invisible, air quality impacts the general public's health. The report noted that 3000 premature deaths per year in the country were from human-made air pollution.

University of Otago associate professor of public health Caroline Shaw said air pollution could cause asthma, heart conditions and increase the rate of cancers, diabetes, dementia and pregnancy-related conditions.

"Basically, with the little particles of air pollution, they get into the body and there is no organ that is not affected by them."

She said the risks increased with exposure - even low levels of pollutants in the air were toxic to the body.

"The only safe level from air pollution is actually no air pollution."

GWRC chair Daran Ponter said New Zealanders tended to lose sight of the problem, especially when comparing air quality with cities around the world.

"But it is nevertheless a present and real issue in New Zealand and certainly in the Wellington CBD and something that we're obligated to tackle through the Resource Management Act - but also as part of being a good public transport provider as well."

Solutions

He suggested tackling the problem by increasing the number of electric vehicles in the city's bus fleet and possibly moving some bus routes along the harbour quays, away from the tall buildings and narrow streets of the Golden Mile where pollutants become trapped.

Committee chair and GWRC councillor Quentin Duthie pointed to the success of electrified public transport in tackling air pollution.

Since 2020 - when a quarter of diesel buses were replaced by electric ones - the concentrations of black carbon and nitrogen dioxide had declined almost by half.

"So we have a good news story in a way in Wellington."

But simply adding more electric buses was not so simple.

"As patronage of public transport continues to rise, which is a good thing and the council is limited in its ability to fund the purchase of new electric buses.

"We're having to meet that demand with more diesel buses and so those pollutants are starting to rise again in those inner city areas.

"So the best thing we can do is to continue to invest in more electrification of the bus fleet through there, which for the regional council that needs central government, that needs the government to assist with that," he said.

Tamsin Mitchell, an air quality scientist and one of the report's authors, said tackling air pollution would take collective action.

She suggested people switch to low-emission forms of heating and transport, or, even better, "actually reducing the need for us to be producing emissions in the first place".

'Make sure there's no perverse outcomes - like they're living in a cold home"

In Wairarapa, the report found Masterton and Carterton recorded more than 50 high-pollution days a year. The World Health Organisation guidelines advise no more than three days a year.

It cited woodburners as the cause of poor air quality.

Particulate matter in the air was shown to be improving slowly because of stricter wood burner standards and the uptake of heat pumps.

The report estimated it would take Masterton 20 years to meet the guidelines for particulate matter in the air.

South Wairarapa District councillor Rachel Clarke said it was important that communities learned to burn winter fuel efficiently and safely. She suggested homeowners considered insulating properties or switching wood burners to cleaner models or to electric heating.

She said the need to tackle air pollution had to be balanced with the financial burden on vulnerable people.

She said targeted support to assist a transition to cleaner home heating would help improve air quality.

Mitchell advocated for a "holistic approach" in tackling pollution from home heating, addressing socio-economic factors which informed people's choices.

"You've got to enable people to be able to change and you've got to support them in that change and you've got to make sure there's no perverse outcomes - like they're living in a cold home."