Why does New Zealand’s air quality get worse in winter?
Air quality declines in winter primarily due to increased use of wood and coal for home heating. Smoke levels are affected by what is burned and how, weather conditions, and the geography of the surrounding landscape. During calm, cold conditions, smoke becomes trapped near the ground, especially in towns located in valleys where temperature inversions are common. This results in higher levels of particulate matter in the air.
What are particulate matter pollutants in our air?
Particulate matter (PM) are small airborne particles generated by human activities and that arise from natural sources. Common activities that lead to particles being released into our air include burning wood for home heating, vehicle exhausts (particularly diesel), road dust, and quarrying.
Natural sources include sea salt, pollen, and wind-blown soil particles including liquefaction dust.
To enable us to compare PM measurements, better understand health impacts, and manage the levels of PM in air, we commonly classify particles by their size in micrometres, i.e. PM10 and PM2.5. Read our factsheet on particulate matter.
What are the health effects of breathing polluted air?
Breathing air that is polluted with fine particles is bad for human health, with the impacts ranging from respiratory illness to high blood pressure, and in the worst cases premature death.
When breathed in, PM10 can cause irritation in the upper airways and affect the heart and lungs. PM2.5 can lodge deep into our lungs and reach the bloodstream, potentially leading to respiratory diseases, heart attacks, lung cancer, and reduced life expectancy. There are health impacts from breathing certain gases in our air too, learn more about the gases monitored by some councils and reported on LAWA.
What are the findings of the LAWA Air Quality National Picture 2025?
The LAWA Air Quality National Picture 2025 presents an overview of particle (PM) air pollution levels, trends, and sources in New Zealand towns that are monitored by regional councils and unitary authorities up to the end of 2024. The summary includes data from monitoring sites measuring particulate matter or gas pollutants.
The 2025 National Picture reveals:
- NZ has relatively good air quality, but in some parts of the country many people are exposed to relatively high levels of PM in winter produced by wood and coal burning for home heating.
- In these areas, the levels of PM can exceed air quality standards or guidelines, and this is usually associated with colder winter days and nights when there is no wind to disperse the PM in the air, or for towns where an inversion layer traps air pollutants.
- In 2024, 40 of 55 sites met the national standard for daily average PM10 (National Environmental Standards for Air Quality – NES-AQ).
- There has been significant improvement over the last decade with 30 of 44 sites with sufficient data showing improving PM10 trends.
- Just 6 of 35 sites met the daily PM2.5 guideline set by the WHO.
- Towns with the highest PM2.5 annual averages include Tokoroa, Pūtāruru, Kaiapoi, and Timaru. This is often due to winter woodsmoke trapped by local geography and weather.
- More sites are now monitoring PM2.5 than in previous years despite it not yet being a regulatory requirement.
Why are PM10 levels in the air generally improved?
Community-led education and awareness programmes are helping households burn cleaner and make informed choices about heating and air quality. Increasing public understanding of the health risks of air pollution has contributed to changes in behaviour, such as burning dry wood only and avoiding outdoor burning. Also, targeted efforts by councils to phase out older wood burners and subsidise cleaner heating, like heat pumps, has helped communities reduce emissions during winter.
LAWA itself plays a role by making air quality data visible, which supports transparency, planning, and public awareness.
These improvements demonstrate that when monitoring leads to action, and when communities and councils collaborate, meaningful change is possible.
Why do regional councils and unitary authorities monitor air quality?
Regional councils and unitary authorities measure outdoor air quality in their regions as part of their responsibilities for managing air quality. National Environmental Standards for Air Quality (NES-AQ) are regulations that set limits in outdoor air for PM10, carbon monoxide, nitrogen dioxide, sulphur dioxide and ozone to provide a minimum level of health protection for all New Zealanders.
Regional councils and unitary authorities report on how levels of air pollutants in their towns compare to the NES-AQ and to international guidelines including for PM2.5.
How do regional councils and unitary authorities monitor air quality?
Air quality monitoring sites are established where pollutant concentrations are expected to be highest and people are affected. Data are logged on site, sent to the relevant councils, and presented directly on LAWA. Learn more.
How can I help to improve air quality in my neighbourhood?
- Use clean heating: Switch from your wood burner to a non-emitting home heating source if possible. Heat pumps, pellet burners, or ultra-low emission burners are better alternatives.
- Burn smokefree: It’s important that if burning wood, the wood is dry, seasoned and non-treated. Get your fire going quickly, keep it burning hot, and don’t damp it down overnight.
- Reduce outdoor burning: Refrain from burning waste outdoors (especially plastic, treated timber and toxic waste).
- Reduce transport emissions: Choose to walk, cycle, or use public transport when possible. Service your car regularly to reduce exhaust fumes. Electric and hybrid cars don’t contribute the same emissions as petrol or diesel vehicles, so if you’re if in the position to switch they’re a great option.
- Report pollution: If you see excessive air pollution that doesn’t look quite right, contact your regional council or unitary authority to report it. Many councils have processes for providing advice to the responsible party, and in serious cases may issue a fine or abatement notice.
What information is on the LAWA Air Quality topic
LAWA presents monitoring results where available for:
- Particulate matter less than 10 micrometres across (PM10)
- Particulate matter less than 2.5 micrometres across (PM2.5)
- Black carbon
- Gases, including sulphur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3) and benzene.
There is also a summary about PM monitoring by region, and you can learn about the main sources of PM and nitrogen oxides by town. You can even explore individual monitoring sites and view real time air quality results. Monitoring site pages include site specific context, history, and a range of data visualisations.
Why does the LAWA project make air quality data freely available?
Regional councils and unitary authorities are required to regularly provide the results of their State of the Environment monitoring. The LAWA project connects New Zealanders with this reporting by making our environmental data open and accessible. By reporting air pollution levels from all long-term monitoring sites in New Zealand in one place, we can inform communities about their air quality, sources, and interventions so they can work together to achieve further improvements.
