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Air Quality

Clean air is vital for supporting a healthy population and environment. Monitoring shows that for most of the year air quality in Otago is very good, with values within the National Environmental Standards for clean air.

During winter months however, temperatures drop and home-heating emissions increase. Coupled with cold and calm weather conditions this leads to poor air quality, particularly in areas of Central Otago.

Otago Regional Council operates a State of the Environment air quality monitoring network throughout the region. Over the past ten years monitoring has focused on airborne particulates less than 10 micrometres across, called PM10.

Recognising the challenges of improving air quality, the council has phased in emission limit rules for domestic heating appliances in Central Otago. The council operates a Clean Heat Clean Air programme to assist residents with switching their old, non-compliant wood burner to a new, approved clean heating appliance. Since it began in 2004, this subsidy has improved over a thousand homes to date.

Long-term trends show air quality is gradually improving in parts of the region (Alexandra, Arrowtown and Clyde), although in other areas it may be declining (Mosgiel and Cromwell).  Not all trends are shown in the table below, as it only shows sites that have been monitored for 10 years.

Otago also has some of the strongest temperature inversion layers in the country. An inversion layer occurs during cold, clear nights when the ground gets colder and cools the air close to it. The warmer air above acts like a lid, trapping the cold, dense air beneath it. This layer can also trap PM10 and with little wind to help disperse the air, the particulates can concentrate and lead to poor air quality. 

Otago Regional Council's Air Quality Strategy can be found here.

Regional Summary
PM10at towns in this region

The most significant air pollutant in New Zealand are small airborne particles in our air (known as particulate matter). Particulate pollutants are of most concern in New Zealand because of their high concentrations in some of our towns. Exposure to high levels of airborne particle pollutants has the potential to cause respiratory and cardiovascular issues. View a factsheet on why air quality is important here.

In some Central Otago towns, PM10 peaks in winter during mornings and evenings when it is coldest and wind is slow. The main source of PM10 is from the burning of solid fuel (i.e. wood) to heat homes. The calm, still conditions of Otago's inland towns mean there is often little ventilation to disperse air pollutants. We are experiencing technical issues with the display of Milton data - these are displaying incorrectly for 2022.  You can find daily data in the downloadable air quality dataset on the download data page, or in the graphs on the Milton site page.


PM monitoring history at towns in this region

  • Annual average
  • Highest daily average
  • Exceedance

What is this showing me?

The graph enables you to view the annual average and highest daily average concentrations of PM10 and number of exceedance days for the year selected. The results are compared to the relevant air quality standard or guideline (denoted by the red horizontal line). See this factsheet for more information about the PM10 measurements, and the standards and guidelines used to report on. 

Values above the standard or guideline shown can be a cause for concern as short- or long-term exposure to high PM10 can have health impacts.  See this factsheet about why air quality is important and factors that influence air quality. 

The trends in the table below indicate whether the PM10 concentrations have been improving, showing no measurable change, or declining over the 10-years prior to the year selected. (For towns that have more than one monitoring site, a representative site is shown).

Data table PM10
Towns 10-year Trend annual average (µg/m³) Highest daily average (µg/m³) 2nd highest daily average (µg/m³) Number of exceedances
Towns 14