environment

Why polluted air will keep killing us

If we want air pollution to stop killing hundreds of Kiwis prematurely each year, our cities need reconfiguring. David Williams reports

The pandemic-enforced lockdown reduced transport-related air pollution, as people traded the car commute for walks and bike rides around their neighbourhoods.

Quieter suburbs have also celebrated the return of bird-song, while clearer waters are rippling with the unusual sight of fish. Streets seemed safer, communities closer-knit.

But like the battle against Covid-19, the war against dirty air isn’t won. In fact, pollution is already climbing towards previous levels – exceeding it in some cases. Nature might be showing us the way, but we appear to be ignoring it, at our peril.

“From a health point of view, a temporary reduction like this doesn’t really mean big health gains,” says Dr Caroline Shaw, a senior lecturer in environmental health at University of Otago, Wellington. “In fact, probably it doesn’t mean a lot of health gain in general because most of the health impacts from air pollution are from long-term exposure.”

If traffic emissions reach previous levels that doesn’t bode well for the fight for climate change, either. To limit global warming to 1.5 degrees Celsius it’s estimated it’ll take a 7.6 percent reduction in greenhouse gas emissions every year between now and 2030.

Some areas of Auckland have experienced an impressive drop in air pollution. Photo: B O'Rourke

Air pollution dropped about three-quarters during the lockdown, to air quality levels that NIWA scientist Ian Longley predicts will take another 15 to 20 years to experience.

(Pollution comprises an invisible and complex mix of gases and miniscule airborne particles, including nitrogen dioxide and particulate matter of varying sizes, known as PM10 and PM2.5. When breathed into the lungs over years they can lead to health problems such as respiratory illness, heart attacks, lung cancer, and strokes.)

Transport emissions are worst in our biggest city, Auckland. Winter air pollution in Christchurch mainly comes from home heating, while Wellington only has pockets of comparatively poor vehicle-related pollution.

Auckland has high concentrations of black carbon, a diesel-related pollutant, which can be two or three times higher than similar sized cities in Europe and North America, and its air pollution-related health costs are $466 million a year.

Studies suggest Auckland’s dirty air results in more than 300 premature deaths a year, and increases hospital admissions for acute respiratory disorders. (Those people are also more vulnerable to the effects of Covid-19.)

Auckland’s air quality improvements during lockdown, therefore, are the most important in the country – for health, and for the country’s future climate policies.

Auckland Council’s assessment of the level four lockdown period shows levels of traffic-associated nitrogen dioxide, which is averaged over a 24-hour period, dropped across eight monitoring sites. The biggest drops were seen at Takapuna (58 percent), and Henderson (57 percent), while a central city site in Queen St declined 33 percent.

                                                                                                                                      Source: Auckland Council

The drop was immediate but levelled off after the first few days. Further declines were experienced in week three. Auckland Council said windy weather after Easter diluted nitrogen dioxide but increased particulate in some places because of dust and sea salt.

Particulate matter comes from various sources, including chimney smoke. Over the level four lockdown, Patumahoe, actually had increased PM10 (8.7 percent). Double digit declines occurred at five sites, with the biggest, 32 percent, at Pakuranga.

                                                                                                                                      Source: Auckland Council

On top of the drop in nitrogen dioxide at Queen St, PM10 and PM2.5 also dropped by more than 10 percent.

Concentrations of pollutants increased at all Auckland sites once level three kicked in.

After its big drop in nitrogen dioxide (NO2), Henderson rebounded with a 108 percent increase. The central city site in Queen St, had the biggest rise in particulates, 41 percent in PM10 and 33 percent in PM2.5.

                                                                                                                                      Source: Auckland Council

Traffic-related NO2 stayed below previous norms. At Takapuna it was 53 percent of the usual level.

Reflecting its varied sources, particulates, in some places, rose to above or near normal levels – “possibly due to wet and windy weather”. Patumahoe was up 119 percent.

                                                                                                                                      Source: Auckland Council

Shaw, of Otago University, says the lockdown reductions in air pollution were so short-lived she doesn’t expect to see any noticeable improvement in long-term health data.

One reason is our baseline levels of air pollution aren’t that high compared with some cities in Europe, China and India. “You might expect to see a short term reduction in mortality if there was a big reduction in the air pollution [in those places], but not in New Zealand.”

However, any long-term reduction on this country’s previous air pollution levels – including below recommended limits – would lead to health improvements, she says, as the relationship between pollution and health is reasonably linear. “The lower you can get your transport-related air pollution, the better.”

Simon Kingham is a professor of human geography at University of Canterbury, and chief science adviser to the Ministry of Transport. He says there’s a chance that, in the short term, congestion will rise in some places, like Christchurch, where public transport isn’t operating at full capacity.

Because of those issues, the Ministry of Transport and the Transport Agency are considering ways to encourage people to walk and cycle more, Kingham says. That might mean staff working from home one day a week – “if you can reduce the number of desks, you can actually reduce your footprint, and that actually saves you money.”

There’s also investigation into the United Kingdom’s cycle to work scheme, which offers tax breaks.

“We do not have serious policy about reducing carbon emissions in the transport sector.” – Caroline Shaw

Already there are signs of the Government working with councils on getting people out of their cars, which feeds into a feeling that some people, post-Covid-19, want their cities to change for good. (It’s not always easy to keep physically distant on public transport, as opposed to walking and cycling.)

Last month, Associate Minister of Transport Julie Anne Genter announced money would be made available to councils to expand footpaths and create temporary cycleways to ensure physical distancing.

In Dunedin, $40,000 was spent painting 450 coloured circles on the main street to encourage physical distancing, which coincided with a speed limit cut to 10km/h. Some city councils, like Wellington, have big ambitions for transport, but, in Auckland’s case, it wants to spend big on projects that don’t fulfil emission reduction targets.

University of Canterbury’s Kingham says not all people can work from home, and walking and cycling won’t suit everyone. “But if you can get 10 percent or 20 percent just to make some of these changes you actually achieve pretty big gains.”

The pandemic has led to worldwide lockdowns of huge swathes of humanity, to prevent a health catastrophe. Governments across the world, including our own, are unleashing billions to rebuild their struggling economies.

Behind all of this, however, is a harder-to-stop and more serious catastrophe – climate change.

(There’s somewhat of a crises crossover, actually. This country’s transport-related greenhouse gas emissions, which have just temporarily dropped, have surged since we signed the Kyoto Protocol climate agreement and now make up half of our annual energy emissions. Kingham says our overall greenhouse gas emissions aren’t expected to drop by much, if at all.)

This country needs to make huge cuts in vehicle emissions to honour our commitments to the Paris Agreement – which aims to keep global warming to below 2 degrees Celsius on pre-industrial levels – and to not undermine the recently passed carbon zero legislation,

Shaw, of University of Otago, says to achieve our emission-reducing goals councils need to start being bolder.

“We have a transport carbon emissions crisis,” she says. “We do not have serious policy about reducing carbon emissions in the transport sector. Our councils need to take this opportunity to start talking about a different vision for our transport futures in cities.”

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