Otago region

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 PM₁₀and 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, PM₁₀peaks 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.

PM monitoring history at towns in this region

Annual average
Highest daily average
Exeedance

Showing:

PM₁₀

Guideline

Concentration

% of guideline

What is this showing me?

The graph shows the annual average and highest daily average PM₁₀ concentrations, and number of exceedance days for the year selected. These are shown against air quality guidelines of 20 µg/m³ for annual averages and 50 µg/m³ for daily averages. The World Health Organisation published new guidelines in September 2021 of 15 µg/m³ for annual averages and 45 µg/m³ for daily averages. Values above the guidelines can be a cause for concern as exposure to high PM₁₀ values can cause short and long term health effects. The trends in the table below indicate whether the PM₁₀ concentrations have been improving, showing no measurable change, or declining over the previous 10-years. (For towns that have more than one monitoring site, a representative site is shown).

Data table PM₁₀