What is fine particulate matter (PM₂.₅) and nitrogen dioxide (NO₂)?
Fine particulate matter (PM2.5) is very small particles in the air, less than 2.5 micrometres in diameter. The main human-made sources of PM2.5 in New Zealand are domestic fires (wood and coal fires for home heating). Other sources include motor vehicles, wind-blown dust, and industry.
When people breathe in PM2.5, it can get lodged deep in their lungs and affect their health. Health impacts from PM2.5 include premature death, hospitalisations (for cardiovascular and respiratory diseases), and restricted activity days.
Nitrogen dioxide (NO2) is a gas in the air. In New Zealand, most human-made NO2 comes from motor vehicles. When people breathe in NO2, it can cause a range of health impacts, including increasing their susceptibility to infections and asthma. Health impacts from NO2 include premature death, hospitalisations (for cardiovascular and respiratory diseases), and childhood asthma.
More than 3,300 deaths from human-made air pollution in 2016
Air pollution does significant harm to many New Zealanders, including children.
In 2016, human-made (anthropogenic) air pollution in New Zealand resulted in an estimated:
- 3,317 premature deaths (in people aged 30+ years)
- 13,155 hospitalisations for cardiovascular and respiratory disease, including 845 hospitalisations for childhood asthma
- 13,229 cases of childhood asthma
- about 1.75 million restricted activity days (days on which people could not do the things they might otherwise have done if air pollution had not been present).
If there was no air pollution (ie. PM2.5 or NO2 from human-made sources) in New Zealand, then about 3,300 deaths would have been avoided in 2016. This represented about 11% of all deaths in New Zealand in 2016.
Air pollution harms were mainly caused by transport and domestic fires – with transport having a much larger impact than previously thought
Motor vehicles were the largest contributor to air pollution health impacts in New Zealand in 2016, with 2,247 deaths (Figure 1). Most of the motor vehicle-related deaths were due to nitrogen dioxide (NO2) (2,025 deaths), with a smaller number due to PM2.5 (222 deaths). The significant impact due to motor vehicle-related NO2 was a new finding for New Zealand.
After motor vehicles, domestic fires were the second largest contributor (962 deaths), followed by wind-blown dust (106 deaths) and industry (2 deaths). These sources all contribute to PM2.5 air pollution.
Figure 1: Number of premature deaths due to human-made air pollution (NO2 and PM2.5) in New Zealand in 2016, by air pollutant and source of air pollution (people aged 30+ years)
Social costs from human-made air pollution were $15.6 billion in 2016
In 2016, the social costs from human-made air pollution were $15.6 billion. These social costs reflect the total cost of all air pollution impacts to New Zealand - not only in terms of direct costs incurred in the health system but also due to loss of life, lost quality of life and lost productivity.
The social costs were mainly from air pollution from motor vehicles ($10.5 billion) (Figure 2). Air pollution from domestic fires resulted in social costs of about $4.6 billion in 2016.
Figure 2: Social costs from human-made air pollution (NO₂ and PM₂.₅) in New Zealand, by air pollutant and source of air pollution, 2016 ($millions)
Largest health impacts of air pollution were in Auckland and Christchurch
In 2016, the territorial authorities (TAs) with the highest number of premature deaths due to air pollution were Auckland City (939 deaths) and Christchurch City (462 deaths) (Figure 3).
Other TAs with high numbers of premature deaths from air pollution included Dunedin City (126 deaths), Tauranga City (107 deaths) and Hamilton City (100 deaths).
Figure 3: Number of premature deaths due to air pollution (PM2.5 and NO2) (among people aged 30+ years), by territorial authority (TA), 2016
The lower South Island had higher rates of premature deaths from air pollution
Accounting for population size, territorial authorities in the lower South Island had higher rates of premature deaths from air pollution (Figure 4).
The highest rates of premature deaths from air pollution were in Invercargill City (219 per 100,000 people aged 30+ years), Christchurch City (206 per 100,000), Waitaki District (191 per 100,000) and Timaru District (186 per 100,000).
Figure 4: Premature deaths due to air pollution (PM2.5 and NO2), rate per 100,000 people aged 30+ years, by territorial authority (TA), 2016
Health impacts from air pollution have increased since 2006, driven by NO₂
From 2006 to 2016, there was an overall increase in deaths, hospitalisations and social costs from human-made air pollution in New Zealand (Table 1). In particular, the number of deaths from human-made air pollution increased from 3,005 to 3,317. The increase in health impacts was driven by nitrogen dioxide (NO2).
Table 1: Changes in health impacts from human-made air pollution (NO2 and PM2.5) in New Zealand, 2006 to 2016 (numbers and rates)
For more information, see Changes over time.
Large proportion of the population exposed to poor quality air, with persisting inequities for Pacific peoples
In 2016, 81.0% of the New Zealand population lived in areas with an annual average PM2.5 exceeding the World Health Organization (WHO) 2021 guideline level (of 5µg/m3) (Figure 5). The proportion was slightly lower among Māori (77.6%), but much higher among Pacific peoples (94.4%), reflecting differences in where they live.
Figure 5: Percentage of population living in areas with PM2.5 higher than WHO 2021 guidelines (5µg/m3), total population and by ethnic group, 2006 and 2016
In 2016, 31.4% of New Zealanders lived in areas with annual average NO2 levels exceeding the WHO 2021 guideline level (of 10µg/m3) (Figure 6). The proportion was lower among Māori (23.1%), but much higher among Pacific peoples (54.5%), again reflecting differences in where they live.
Figure 6: Percentage of population living in areas with NO₂ higher than WHO 2021 guideline (10µg/m3), total population and by ethnic group, 2006 and 2016
For more information, see Exposure to poor air quality.
Information about the data
This data is from the Health and Air Pollution in New Zealand (HAPINZ 3.0) study, published in July 2022 (Kuschel et al 2022). For more information from the HAPINZ study, see the HAPINZ 3.0 webpages and the Ministry for the Environment HAPINZ webpage.