ORC’s Scientist – Air Quality, Sarah Harrison says “Concentrations of particulate matter, an air pollutant measured by ORC, vary year to year and many Otago towns have the geography and climate that allows pollution to build up, rather than disperse.”

“Exceedances of the national air quality standards are generally due to a combination of emissions, the environment they are emitted into, and the local weather situation on the day.”

Due to large-scale climate cycles such as the phases of El Nino and La Nina, some winters are “worse” than others, creating more opportunities for pollution to build up, whether that be lower temperatures, lower wind speeds or a combination of both. 

These episodes occur on average every few years and can last from one to two years, Ms Harrison says, 
“We also see more instances of natural inversions layers throughout winter where the weather can act like a blanket, trapping pollution close to the ground. Normally, warm air rises and takes pollution with it, but in winter, cold air gets stuck under the warmer air, holding the pollution near where people breathe,” Ms Harrison says.

Air quality is generally worse in winter due to an increase in the use of fireplaces for home heating. In addition, cars give off more pollution because they take longer to warm up in the colder weather.
 
“The majority of emissions in winter come from fireplaces for home heating. We know this because of the extreme seasonal patterns we see in the data each year.

These breaches of ambient air quality were all publicly reported in the ODT, as required under the National Environmental Standards for Air Quality (NESAQ, 2004).

The NESAQ requires ORC to measure particulate matter emitted into the air with a diameter of 10 micrometres or less (PM¹⁰). That is about a fifth of the width of a human hair.

PM10 includes solid or liquid particles from vehicle, industry, and home heating emissions such as wood fires, as well as from natural sources.

To understand our air quality in relation to the NESAQ, ORC undertake a continuous air quality monitoring programme. This winter we found there were 37 breaches of national air quality standards - 11 in Alexandra, 25 in Arrowtown and one in Mosgiel.

The NESAQ for 24-hour PM¹⁰ is 50 micrograms per cubic metre of air (µg/m³). Below is a graph that shows the number of times in the last in the last five years when PM¹⁰ has gone beyond this limit.

ORC continually monitors these areas, and often conducts further research in other parts of Otago that helps determine where PM hotspots are and how these concentrations could be reduced. This includes completing low-cost sensor monitoring in Milton earlier this year with the team from NIWA. Additional temporary monitoring was also undertaken in Wanaka and Queenstown to support data from ORC’s new monitoring sites in these areas.

“An increase in air quality studies, monitoring sites, and upgrades of instruments will all help to better monitor the finer PM^2.5 and focus on combustion-related sources of particulate matter such as home heating and traffic,” Ms Harrison says.

Monitoring data can be found on the Otago air quality page on the LAWA (Land Air Water Aotearoa) website.

Regional Plan: Air and Air Quality Strategy review

ORC is currently refreshing its approach to managing air quality. This includes updating its Air Quality Strategy, which provides the overview of how ORC is working to improve air quality, and reviewing its current Regional Plan: Air, which provides the regulations to manage and improve air quality.

Staff from ORC’s Policy and Planning Team and Strategy Team have mapped the process for developing the revised Plan and Strategy and presented to council at last Wednesday’s Council meeting.

This timeline sees the draft Strategy and draft Plan being ready for Council endorsement prior to public notification of the Plan and public consultation on the Strategy in the second half of 2025.

At last Wednesday’s Council meeting, Councillors approved the establishment of a Councillor Reference Group to oversee the process of updating the Plan and the Strategy. The team working on the Strategy and the Plan will work with this Councillor Reference Group to provide updates on progress and ensure information provided to Council is tailored to support efficient decision making, thereby maximising the value of full Council meetings and workshops.

Air quality engagement (Jul-Aug 2024)

While Otago has made progress in improving air quality in recent years, science shows we need to rethink how air-related activities are carried out.

Through ORC’s monitoring and research, it has a very good understanding of what is affecting air quality and what could be done about it.

These air quality issues and suggested approaches to improve local air quality were shared with communities across Otago for their feedback at a series of drop-in sessions between 29 July and 22 August.

People were encouraged to give their feedback in a survey as well as share some information around their burning habits. More than 550 responses were received online and in-person.

The update of the Air Quality Strategy and Regional Plan: Air includes considering whether more rigorous rules are needed to improve air quality in the region’s urban areas and scoping several approaches for council to consider.

This will be publicly available and, along with Council’s feedback on it, will inform the development of a refreshed approach to air quality management.

Burn Dry Breathe Easy

Ms Harrison has said in the past “We have some of the worst ambient air particulate matter (PM) concentrations in the country. PM, like other air pollutants, is very dangerous to our health and responsible for large numbers of premature deaths as well as respiratory and cardiovascular disease.

“It is for reasons like these that ORC’s annual Burn Dry, Breathe Easy campaign in the lead up to winter is so important,” she says.

A warm home is vital in cold Otago winters, and burning wood or coal has been one of the cheapest ways to keep out the chill. Unfortunately, all fuels and burners are not created equal, and the fuels and burner technology people use have a huge influence on air quality.

There are a number of things we can all be doing things to help reduce the current levels of particulate matter including replacing older wood burners, open fires, and multi-fuel burners with ultra-low emission burners, or better yet, looking into alternative heating such as pellet burners or heat pumps.