Monitoring and reporting on air quality

This page has information on the monitoring of air quality and access to the latest national and regional air quality data.

Latest regional airshed information

Access the latest air quality data at a national and regional level on the Land, Air, Water Aotearoa website. 

About air quality in New Zealand

Although New Zealand’s air quality is mostly good, there are times when the air in urban areas is affected by pollution. The pollutants most commonly affecting our urban air are particles called PM10 and PM2.5Air pollution can affect people’s health so National Environmental Standards for Air Quality were introduced in 2004 to set acceptable levels for air quality.

Identifying airsheds

Regional councils and unitary authorities have identified 72 areas where air quality could reach levels higher than the national air quality standards. These areas are called airsheds.

Airsheds have been identified based on councils knowledge of existing air quality data and the location of significant sources and factors that affect the spread of pollution (such as local geography and weather). These airsheds have been published in the New Zealand Gazette.

All but one of the 72 airsheds were gazetted because of known or potential concerns about levels of smoke and soot (PM10) at certain times of the year. The remaining airshed at Marsden Point in Northland has the potential to breach the sulphur dioxide and PM10 standard.

Gazetted airsheds include areas where the PM10 standard is regularly breached each year, and a smaller number that have the potential to breach the standard unless carefully managed.

Councils have taken a number of approaches to defining airsheds in their region. An airshed may be based on one of the following:

  • urban areas where pollution levels may be high
  • a portion of the region covering more than one urban area
  • an area with separate, but similar, urban areas grouped together.

In most cases, airsheds are towns or cities, though in some areas they may include a number of towns – for example, the Otago 1 airshed combines Alexandra, Arrowtown, Clyde and Cromwell.  

The path towards complying with the PM10 standard

The PM10 standard sets a maximum concentration of 50 micrograms per cubic metre (50µg/m3) over a 24 hour period. Levels above the standard, when concentrations are unacceptably high, are known as exceedances. The PM10 standard permits only one exceedance in a 12 month period.

Councils managing airsheds that breach the standard must plan for how to improve air quality to meet the timeframes that apply to the airshed based on the NES.

Monitoring air quality in airsheds

To track air quality in airsheds councils carry out monitoring. Monitoring is carried out where pollution levels are highest in an airshed. It is impractical to measure air quality everywhere as the air quality standards require sophisticated scientific equipment and round-the-clock monitoring.

To comply with the air quality standards many councils have had to upgrade monitoring equipment. Equipment that typically measured one day in three has been replaced by fully automated equipment that monitors continuously.

PM10 in the urban air

PM10 is ‘particulate matter’ that is smaller than 10 micrometers across – small enough to enter the tiniest passage of people’s respiratory systems. Some PM10, such as sea salts and dust, occur naturally and some is produced when people burn fuels such as coal, wood, oil, petrol and diesel. The main sources in the urban environment are home heating and vehicles, as well as some industrial processes.

The level of PM10 in the air depends on how much pollution is being produced (the emissions). However, other factors like the weather and local geography have a big effect. For example, windy conditions help move pollution away but features such as valleys can cause pollution to linger.

Temperature inversions which occur during cold, calm conditions can trap in pollution causing levels to be high. Years where there have been a lot of temperature inversions often have worse air quality than colder windier years even though people may have used their wood burners more often, and produced more PM10 in the colder year. 

It is important to remember these effects when trying to assess improvements in air quality.