This section provides background to Our air 2021, including why understanding the quality of our air is important. It also provides information on the legislation and guidelines this report makes comparisons against.

Photo of a mountain biker at a lookout, overlooking the city and harbour of Dunedin. It is a sunny, blue sky day.
Overlooking Dunedin.

Image: Clare Toia–Bailey,

About Our air 2021

This release of Our air 2021 supersedes the earlier report Our air 2021: preliminary data release, released in October 2021. The earlier report was required to be published to meet statutory obligations, but due to its timing, it was not able to include evaluations of the data against the World Health Organization’s 2021 air quality guidelines, and was therefore preliminary only. This updated report includes comparisons to these new guidelines, providing a more comprehensive understanding of the health impacts from air pollution based on the latest science.

Our air 2021 is the latest in a series of environmental reports produced by the Ministry for the Environment and Stats NZ. It is the third report in the series dedicated to air quality, following the 2014 and 2018 air domain reports, and is the second released under the Environmental Reporting Act 2015.

In 2019, the Parliamentary Commissioner for the Environment released his report, Focusing Aotearoa New Zealand’s environmental reporting system [PCE website]. The report identified how the environmental reporting system can be improved and recommended changes to the Environmental Reporting Act. These amendments will provide a stronger foundation to ensure we understand our environment and the impacts people are having on it.

Our air 2021 is a report in a transitional format to meet statutory requirements while we make the fundamental changes to the reporting system that have been recommended. This is a data-oriented release, with the primary focus on updating indicators. This report updates some of the indicators reported on in previous years but does not introduce new ones. Interactive graphs and maps can be found on the Stats NZ website (linked at the bottom of each indicator section of this report).

Understanding air and wellbeing

We often take the air we breathe for granted, yet clean air is essential to our wellbeing. Air can become contaminated by particulate matter (particles suspended in the air) and gaseous pollutants. This can negatively affect human health, our quality of life, and natural ecosystems. Poor air quality can become a serious public health issue, with significant costs to society. Our air 2021 reports on the emissions generated by a range of activities in Aotearoa New Zealand.

Greenhouse gas emissions and their impacts are not reported on within Our air 2021 but can be found in Our atmosphere and climate 2020.

Standards we report against

This report evaluates monitored data against two primary standards or guidelines – one national and one international – to indicate potential impacts on human health.

The World Health Organization guidelines [WHO website] are based on an evaluation of the most recent science on health impacts from air pollution, and identify air pollution levels above which there are significant risks to human health. This is the only consideration used for setting the guideline levels. They are intended to inform air quality management, but, as international guidelines, are not legally binding.

In contrast, the National Environmental Standards for Air Quality (NESAQ) set legally binding levels of air pollution that must not be exceeded. The levels at which these standards are set are informed by international research and guidelines (such as the World Health Organization guidelines), but can also take into account other considerations, such as cost and feasibility of meeting the standard.

National Environmental Standards for Air Quality

The National Environmental Standards for Air Quality are regulations made under the Resource Management Act 1991. Under the standards, limits for particulate matter and gaseous pollutants are defined to protect communities against detrimental health impacts. The standards focus on short-term exposure – that is, average concentrations over hourly or 24-hour time periods. The standards allow some pollutants to be above their threshold limits (ie an exceedance) a limited number of times per year.

World Health Organization air quality guidelines

While the National Environmental Standards for Air Quality have a short-term exposure focus, the World Health Organization (WHO) air quality guidelines (AQGs) also provide indicative limits to protect communities from the long-term or chronic health impacts of air pollution in addition to short-term exposure guidelines. The WHO guidelines are based on a synthesis of research on the health effects of air pollutants. Many regional councils and unitary authorities, which are responsible for monitoring and managing air quality in New Zealand, choose to report on levels of air pollutants against the WHO guidelines, in addition to the National Environmental Standards.

During the final production stages of Our air 2021, the WHO released updated air quality guidelines (WHO, 2021). This is the first update in 16 years and is a result of a systematic review of more than 500 publications by world experts. As such, it builds on the advances in measurement and pollution assessment from a global database as well as epidemiological studies (WHO, 2021).

In most cases the revised 2021 WHO air quality guidelines are more stringent than the 2005 ones (WHO, 2006), reflecting the large body of evidence of detrimental effects of key pollutants on human health, even at low levels (table 1).

Table 1: Comparison of recommended 2005 and 2021 World Health Organization air quality guideline levels

Pollutant Time period 2005 air quality guideline 2021 air quality guideline Units

Particulate matter

2.5 μm (PM2.5)

Annual 10 5 μg/m3
24-houra 25 15 μg/m3

Particulate matter

10 μm (PM10)

Annual 20 15 μg/m3
24-houra 50 45 μg/m3
Ozone (O3) Peak seasonb 60 μg/m3
8-hour 100 100 μg/m3
Nitrogen dioxide (NO2) Annual 40 10 μg/m3
24-houra 25 μg/m3
Sulphur dioxide (SO2) 24-houra 20 40 μg/m3
Carbon monoxide (CO) 24-houra 4 mg/m3


  • a: 99th percentile (ie 3–4 exceedance days per year)

  • b: Average of daily maximum 8-hour mean O3 concentration in the six consecutive months with the highest six-month running-average O3 concentration

  • μg/m3: micrograms per cubic metre

  • mg/m3: milligrams per cubic metre.


Our air 2021 assesses New Zealand’s air quality against both the 2005 and 2021 WHO air quality guidelines. This report has included reference to the 2005 WHO air quality guidelines because these have been the reference thresholds for air quality measurements across New Zealand to date, and because this allows comparison to findings in Our air 2018.

We have also assessed our data against the revised 2021 WHO air quality guidelines, to enable us to evaluate New Zealand’s air quality using the most up-to-date scientific understanding of good air quality.

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