The air we breathe: Our urgent problem with heating and vehicles

While there was initially a lot of concern about one type of pollution, it turned out we should have been a lot more ...

While there was initially a lot of concern about one type of pollution, it turned out we should have been a lot more concerned about another.

In part one of our 'Air We Breathe' series, Michael Daly explains the urgent problem with our air quality rules.

Coming up with rules to keep New Zealand's air clean has proven remarkably difficult, and as the process limps along, vehicle emissions are heading in the wrong direction.

Failure to come to grips with air pollution means the air in some towns too often becomes unhealthy on cold, calm nights when residents stoke up their wood and coal fires. It's also visible in the characteristic brown haze that can be seen hovering around Auckland on a polluted day.

A 2012 report prepared for several government agencies estimated 1175 people in New Zealand die prematurely each year due to air pollution from human-generated sources. There are also thought to be around 600 extra hospital admissions for respiratory and cardiac illnesses and 1.49 million restricted activity days, when people can't do what they otherwise might have done if the air wasn't polluted.

DRIVING POLLUTION

Nitrogen dioxide - used as a general proxy for air pollution from vehicles - rose an overall 17 per cent across between 2007 and 2015 across sites monitored by the NZ Transport Agency. Most of that increase was at the beginning of the period, with the rise between 2010 and 2015 down to 1 per cent.

But the averages obscure much bigger changes at specific sites. Those movements ranged from a 10 per cent decline to a 55 per cent lift over the whole period, while from 2010-2015 the range was from a 20 per cent fall to a 30 per cent gain.

Much of the monitoring done across New Zealand measures tiny particles called particulate matter, much of which comes from the burning of coal and wood for heat. The problem has been particularly highlighted in Christchurch over the years but it has been an issue in many towns and remains a problem, although gains are being made.

Particulate matter is commonly measured in two size categories - PM10 with a diameter of less than 10 microns (millionths of a metre), and PM2.5.

MOVING TARGETS

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Efforts to get on top of the problem go back well over a decade, with the Labour government introducing national environmental standards for air quality back in 2004.

Those included a standard for PM10. The intention was that by 2013 no place would have more than one day a year where PM10 levels topped 50 micrograms per cubic metre - written µg/m3 - as a 24-hour average.

Then in 2009 - several years before the PM10 standard was even due to come into force - Environment Minister Nick Smith, in what was then a National-led government, announced a review.

The review focused particularly on the PM10 standard, with concerns it was too stringent and some areas would not be able to meet the timetable.

An amendment in mid-2011 extended the target date to September 2016 for some areas. After that date, the worst offenders were also supposed to only pass the target level three times a year, with the one-day target for those places put off to September 2020.

But the indecision is not over yet. A Government review of the particulate matter standard is under way, looking at the costs of compliance and the latest science on health impacts. That work is due to be finished late this year.

SMALLER PARTICLES, BIGGER PROBLEMS 

Part of the problem with the standard was identified by Parliamentary Commissioner for the Environment Dr Jan Wright in a 2015 report.

It turns out the standard was aimed at the least important of four guidelines for particulate matter set by the World Health Organisation.

New Zealand's limit was based on short-term exposure to the larger of the particles commonly monitored, but what is most important is long-term exposure to the finer particles - PM2.5.

"The smaller airborne particles are, the greater is the risk to those who inhale them. Similarly, it has been discovered over time that the health impacts of long-term exposure to particulates are much greater at a population level than the impacts of short-term exposure," Wright said.

That qualification aside, the places that have been given until 2020 to meet the particulate standard are Ashburton, Christchurch, Hastings, Invercargill, Kaiapoi, part of Nelson, some towns in Otago, Reefton, Richmond, Rotorua, Timaru, Tokoroa and Waimate.

Some are struggling and others are looking promising. In 2016, Timaru went over the standard's PM10 limit 26 times, Kaiapoi 7, Christchurch 5, Ashburton 2, Waimate none, Alexandra 38 times, Arrowtown 32, Milton 35, Reefton 4 times, Hastings 7, Richmond 5, Rotorua 3. There's also a problem in Masterton, with a monitoring site in the east of the town recording 10 days in 2016 when the PM10 limit was exceeded, compared to one day in the west of the town.

With nitrogen dioxide, the WHO's annual guideline is 40 µg/m3 (micrograms per cubic metre). That limit was exceeded in 2015 by two monitoring sites - both in Hamilton - of the 128 sites monitored by NZTA. At the intersection of Lorne St and Ohaupo Rd in Melville, the measure was 41.4µg/m3 , and at the intersection of Greenwood st and Killarney Rd, Frankton it was 42.2.

NZTA said apart from those two sites, most of the other locations with high concentrations were in Auckland, Wellington and Christchurch. Planned projects would improve traffic flows at most of those sites.

 - Stuff

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