Fires, car fumes blight air quality

Warming our homes in winter with wood and coal, and the fumes we pump from our cars, remain the biggest threats to New Zealand’s air quality.

But a new report shows pollution levels have been dropping in many areas.

The latest stocktake report by the Ministry for the Environment and Stats NZ showed that while some problems persisted, progress has been made and levels of some pollutants were declining.

“The report shows that using wood and coal burners to heat homes in winter continues to cause issues in some places,” Government Statistician Liz MacPherson said.

“This remains the largest single cause of human-generated poor air quality in New Zealand.”

While air quality was good in most places and at most times of the year, in cooler months, emissions from home heating could raise levels of human-made source of particles suspended in the air, or particulate matter (PM), above standards and guidelines.

The national emissions inventory indicates burning wood and coal for home heating was the biggest single source in 2015, making up one quarter of PM10 (particles less than 10 micrometres) and 33 per cent of PM2.5 (particles less than 2.5 micrometres).

Data from monitoring sites indicate air quality is poorer in autumn and winter when temperatures were cooler.

From 2007 to 2016, 79 per cent of instances when PM10 and PM2.5 were higher than guidelines occurred during winter.

However, monthly average PM10 Evidence is increasing that ultrafine particulate matter — that smaller than 0.1 micrometres — is a threat to good health.

The tiny material comes from car exhausts, home heating and forest fires.

It gets deposited in people’s lungs, and the small size means they enter the bloodstream and move around the body causing cellular and genetic damage.

Little is known because longterm studies on health effects are not yet available.

Ammonia, from intense farming,

concentrations between 2007 and 2016 have seen increasing trends in 17 of 39 monitoring areas, or “airsheds”, in winter, when home-heating emissions were at their highest.

Arsenic levels in our air also is another threat identified in the report.

International research shows that excess nitrogen as ammonia can acidify soil and cause changes in biodiversity by creating nutrient imbalances that favour one species over another, often favouring exotic species over natives.

Because soils in New Zealand tend to be naturally low in nitrogen, even small increases have the potential to harm biodiversity and ecosystems.

Yet another potential issue was

peaked in winter when people burn treated wood for home heating.

“The report also shows vehicle emissions as a leading cause of poor air quality in some places,” McPherson said. sulphur dioxide emissions from a growing number of ships visiting the country.

Studies in Auckland had found that sulphur dioxide concentrations were higher near the waterfront and are highest when the wind comes from the direction of the port.

Tracer studies that could “fingerprint” emissions from shipping by measuring nickel and vanadium, which were predominantly associated with shipping emissions, found the highest levels near the water.

Vehicle emissions contributed to poor air quality in places, particularly for nitrogen dioxide pollution, which could cause serious health problems.

While data indicated vehicles were the single biggest source of human- generated nitrogen oxides in 2015, at 39 per cent, it also showed a slightly decreasing trend in Auckland, Bay of Plenty, Hamilton, Northland, and Wellington between 2004 and 2016.

MacPherson called this a “welcome sign”, and something that had led to a slight health improvement.

International studies show that air pollution can affect people’s health in many ways.

Effects included shortness of breath and coughing, heart attack, stroke, diabetes and premature death.

New Zealand-specific studies on the health impacts were limited, but modelled data provides information on the changes over time.

In 2016, modelled data estimated the number of premature adult deaths per 100,000 people from exposure to PM10 in New Zealand was 8 per cent lower than in 2006.

The number of days per 100,000 people when people were not able to go about their regular daily activities was 12 per cent lower.

But relative improvements in air pollution effects appeared to be largely due to more people living in areas with lower PM10, such as Auckland, rather than a drop in PM10.

“The overall news is good, but we [have] specific issues to address,” said the Ministry for the Environment’s deputy secretary, Amanda Moran.

“Technology changes, for example improved wood burners or electric vehicles, will help but we also need to change our behaviours, like getting out of our cars and being careful what we burn.

“We need to ensure the National Environmental Standard that covers this area remains fit for purpose and that all areas of government policymaking, such as transport policy or urban planning, take air quality issues into account.”