Summary of key findings

PM₁₀ (particulate matter of 10 micrometres diameter or less)

PM₁₀ concentrations at most locations measured (69 percent) have improved since 2011, but sites still have high concentrations at times – 76 percent were higher than the 24-hour 2021 World Health Organization (WHO) air quality guidelines at least once between 2017 and 2020, and almost half were higher than the 2021 WHO air quality guidelines for annual PM₁₀ exposure.

PM_2.5 (particulate matter of 2.5 micrometres diameter or less)

PM_2.5 concentrations at 50 percent of locations have improved since 2011. However, 95 percent of sites were higher than the 24-hour and annual 2021 WHO air quality guidelines at least once between 2017 and 2020. The sites with the highest PM_2.5 concentrations were above the guideline for around a quarter of the year. These high concentrations generally occurred during the colder months.

Nitrogen dioxide

Nitrogen dioxide concentrations at most locations (86 percent) have improved since 2011. But five of seven sites (71 percent) were higher than the 24-hour 2021 WHO air quality guidelines at least once between 2017 and 2020, and two of these sites (both in high-traffic areas) were higher than the air quality guidelines an average of 300 days and 235 days respectively per year.

Sulphur dioxide

Sulphur dioxide concentrations have improved at most locations (80 percent) since 2011. Sulphur dioxide concentrations still exceed air quality guidelines near some industrial sources.

Ground-level ozone

Ozone concentrations in New Zealand are quite low compared to levels recorded in many other countries. Trends could only be determined at one of the two sites, with the trend direction being 'indeterminate', meaning there was not enough statistical certainty to determine a trend direction. At this site, concentrations came very close to exceeding the peak season 2021 WHO air quality guidelines.

Carbon monoxide

Carbon monoxide concentrations at most locations (90 percent) have improved since 2011. Between 2017 and 2020, no sites exceeded the National Environmental Standards for Air Quality or WHO air quality guidelines.

Air pollutant emissions (sources)

Wood burning for home heating is a major source of air pollution in New Zealand. Most particulate matter from wood smoke is PM_2.5 (which is more harmful to human health than PM₁₀, due to its smaller particle size) and most is emitted in winter. Combustion in the manufacturing industries and construction is another large source of PM_2.5. Dust from unsealed roads contributes substantially to PM₁₀, although there is uncertainty around the exact magnitude of these emissions.

Motor vehicle emissions continue to contribute to poor air quality in many urban areas (primarily in the form of PM_2.5, nitrogen dioxide, and carbon monoxide). Whereas emissions of some pollutants have reduced due to improved engine technology and fuel quality, many improvements have been offset by higher traffic volumes, more distance traveled, and intensification along transport corridors. In addition, vehicles are getting heavier, with larger engines.

Health impacts

In New Zealand, poor air quality results in significant human health impacts. While the relative impacts per 100,000 people appear to have improved between 2006 and 2016, the absolute number of people affected has increased due to population growth.

Note: We anticipate that this indicator will be updated in 2022, pending an update to the Health and Air Pollution in New Zealand model.

COVID-19 lockdown (2020) impacts on air quality

Restrictions implemented in 2020 during the COVID-19 pandemic temporarily decreased concentrations of several key pollutants across the country. Nitrogen dioxide, primarily generated by the combustion of fuel by motor vehicles, showed more of a decrease than particulate matter pollution, which comes from a range of sources. Nitrogen dioxide concentrations decreased by approximately half due to reduced vehicle traffic.