New Zealand’s air quality is generally considered good most of the time. Particulate pollutants are of most concern in New Zealand, because of their high concentrations in some locations and their potential to cause serious health problems.
The following section looks at the data relating to pollutants in our air, how we compare with other countries, and what changes we are seeing over time.
Airborne particles – the pollutants of most concern in New Zealand
Our PM10 concentrations are low compared with other countries. In 2011, our annual average PM10 concentration was the seventh-lowest of 34 Organisation for Economic Co-operation and Development (OECD) countries (a group of countries with similar levels of economic development to New Zealand). This comparison is indicative only, as some countries have a different monitoring approach. However, it shows that air quality in New Zealand is on average ‘good’ compared with most developed countries.
New Zealand’s relatively small population and limited level of heavy industry contribute to our comparatively good air quality. However, climatic and geographical factors are also important. New Zealand is relatively windy, which helps to disperse pollutants. Our isolation from other countries means we are insulated from all but the more major sources of pollution from other countries (such as large forest fires in Australia) and so most of the air quality issues we experience are from local activities.
For more detail see Environmental indicators Te taiao Aotearoa: Annual average PM10 concentrations in OECD countries (urban areas).
Our towns and cities rate well against WHO long-term guideline but not against short-term guideline
Our towns and cities generally measure up well against the WHO long-term guideline for average particulate concentrations (PM10), but not as well against the WHO short-term guideline.
In 2013, 45 (85 percent) of the 53 sites monitored met the WHO long-term (annual) guideline (see figure 6). Of the eight sites that exceeded the guideline, six were in towns and cities in the South Island, and home heating was the likely cause of these high concentrations. Of the two remaining sites, one was a busy urban road in Auckland (Khyber Pass Road), while the other was an industrial area in Hawke’s Bay, where the air has a high level of airborne sea salt (a natural source of PM10).
In contrast, more than half (21) of the 37 monitored airsheds (an area managed for air quality) exceeded the national short-term standard (which is based on the WHO short-term guideline) on two or more days in 2013 (see figure 7). When comparing against this standard, air quality is measured over a 24-hour period.
Note: Results at these monitoring sites do not necessarily represent the whole location. PM10 – particulate matter 10 micrometres or less in diameter. PM10 concentrations are in micrograms per cubic metre of air (µg/m3). The WHO guideline is exceeded when concentrations are above 20 µg/m3. Data from regional councils of Northland, Bay of Plenty, Waikato, Hawke’s Bay, Manawatu-Wanganui, Wellington, Canterbury, West Coast, Otago, Southland; district councils of Marlborough and Tasman; Nelson City Council; Auckland Council.
This map illustrates the magnitude of PM10 concentrations of airborne pollutants at monitoring sites across New Zealand in 2013. Visit the MfE data service for the full breakdown of the data.
Note: Results shown for an airshed are not always the same for the whole airshed. An airshed is a defined area managed for air quality. An airshed can include a number of monitoring sites. PM10 – particulate matter 10 micrometres or less in diameter. Data from regional councils of Northland, Bay of Plenty, Waikato, Hawke’s Bay, Manawatu-Wanganui, Wellington, Canterbury, West Coast, Otago, Southland; district councils of Marlborough and Tasman; Nelson City Council; Auckland Council.
This map illustrates PM10 exceedances in airsheds across New Zealand in 2013. Visit the MfE data service for the full breakdown of the data.
When we measure concentrations against the long-term guideline, we measure air quality throughout the year – including times of high and low air pollution – with results showing the long-term (average) exposure at a particular location. When we measure against the short-term standard, this identifies times when air pollution is high.
The difference between long- and short-term results reflects the nature of air quality issues in New Zealand, as outlined in the Overview. Exceedances of the short-term standard are primarily a winter issue: 95 percent of all exceedances occurred in winter (see figure 8). This can be attributed to higher emissions from burning wood or coal for home heating, and calmer weather conditions that slow the dispersal of pollutants.
Note: PM10 – particulate matter 10 micrometres or less in diameter. Data from regional councils of Northland, Bay of Plenty, Waikato, Hawke’s Bay, Manawatu-Wanganui, Wellington, Canterbury, West Coast, Otago, Southland; district councils of Marlborough and Tasman; Nelson City Council; Auckland Council.
This graph shows the percentage of the total number of days PM10 exceeded the national daily standard by month over the period 2011 to 2013. Visit the MfE data service for the full breakdown of the data.
Overall, the South Island had higher PM10 annual concentrations and more airsheds that exceeded the national short-term standard (ie 14 of the 20 exceeding airsheds in 2013). This is due to the greater use of wood and coal for home heating. Meteorological conditions (influenced by topography) can be a factor in some locations. For instance, Christchurch is sometimes affected by an inversion layer, where a layer of warm air traps cooler air and any pollution underneath.
For more detail visit Environmental indicators Te taiao Aotearoa: Annual average PM10 concentrations in towns and cities, Seasonality of PM10 exceedances, and PM10 daily concentrations.
Most sites exceeding guidelines for PM2.5 are in urban areas
In 2013, 4 of the 10 sites monitored for PM2.5 exceeded the WHO long-term guideline, while seven exceeded the daily guideline.
The seven sites that exceeded the daily guideline did so for between 1 and 55 days. Of these exceedances, 96 percent occurred during winter. Like PM10, we can attribute these exceedances largely to home-heating emissions and calm weather conditions.
PM2.5 monitoring is not mandatory, so we cannot report on it at a national level. It is monitored only at 10 sites in the Auckland, Wellington, and Canterbury regions.
Because PM2.5 is a subset of PM10, when high concentrations of PM10 occur at a site (usually urban sites), high PM2.5 concentrations are also likely to occur.
For more detail visit Environmental indicators Te taiao Aotearoa: PM2.5 concentrations.
Particulate pollutants in our air are decreasing over time
Concentrations of particulate matter in our air have been decreasing over time.
Nationally, we only have comprehensive data from 2006. From 2006 to 2013, New Zealand’s annual average PM10 concentration decreased 8 percent – a statistically significant decrease. Just under one-third of the monitored sites (14 of 44) showed a statistically significant decrease in annual concentrations over this period.
For more detail see Environmental indicators Te taiao Aotearoa: PM10 annual average concentrations.
Local data from Auckland indicate a decrease in concentrations of particulate matter over a longer time-scale (from 1965). Until 1999, total suspended particles (TSP) rather than PM10 was measured in Auckland, and only TSP is shown in figure 9. This is a measure of all airborne particulate matter up to 100 microns, of which PM10 is a subset.
Note: Concentrations are in micrograms per cubic metre of air (µg/m3).
This graph shows the monthly total suspended particulate (TSP) concentrations in Auckland between 1965 and 2013. Visit the MfE data service for the full breakdown of the data.
This decrease in particulate matter is likely due to stricter controls and monitoring of industrial and other emissions from the 1970s, a steady shift from open fires to ‘cleaner’ forms of home heating, improvements to vehicle fuel, and stricter emission limits for new vehicles.
For more detail see Environmental indicators Te taiao Aotearoa: Total suspended particulate concentrations in Auckland.
Nitrogen dioxide and other pollutants in our air
Nitrogen dioxide generally meets the WHO guideline
The main source of nitrogen oxides (including nitrogen dioxide) is motor vehicles.
In 2013, 97 percent of 122 monitored sites likely met the WHO long-term guideline (measured using screening methods) for nitrogen dioxide. Between 2010 and 2013, 3 to 6 sites (about 2–5 percent of sites) ‘likely’ exceeded this guideline in each of these four years.
The ‘likely’ exceedances occurred close to busy local roads and state highways in major urban centres (Auckland, Hamilton, Wellington, and Christchurch). No ‘likely’ exceedances occurred at monitored urban areas away from busy roads, and concentrations were much lower than those at busy local roads and state highways.
For more detail see Environmental indicators: Te taiao Aotearoa: Nitrogen dioxide concentrations.
Other pollutants exceed health guidelines at some locations
We have only limited data on other pollutants. In some urban locations, concentrations of arsenic and benzo(a)pyrene (associated with cancer and irritation of the ear, nose, and throat) ‘likely’ exceeded Ministry for the Environment’s long-term guidelines. These ‘likely’ exceedances are probably due to emissions from burning wood or coal for home heating.
Other pollutants exceeded guideline levels at certain locations. Sulphur dioxide (associated with respiratory problems) exceeded the short-term guideline at 4 of the 8 monitored locations in 2013. The four sites exceeded the guideline between 1 and 65 days of the year. The four sites were three industrial locations (Mount Maunganui, Woolston in Christchurch, and Timaru) and one port location (Auckland waterfront).
In 2013, no exceedances of the Ministry for the Environment’s long-term guideline occurred at the eight sites monitoring benzene. However, one of these sites (Khyber Pass Road, Auckland) exceeded in 2012.
Carbon monoxide, lead, and ground-level ozone generally meet health guidelines
Limited monitoring of other pollutants between 2007 and 2013 indicate that concentrations met the guidelines or standards for these pollutants:
- carbon monoxide (can aggravate heart conditions)
- lead (can affect the nervous system and impair mental development in children)
- ground-level ozone (associated with increased respiratory and cardiovascular conditions)
- busy transport locations for carbon monoxide and lead (of greater concern historically, before leaded petrol was phased out in 1996)
- locations at a distance from busy transport sites (because it takes time for the chemical reactions that create ozone to occur, and for chemicals to disperse away from their source).
These results suggest that concentrations of these pollutants at other sites would be unlikely to exceed health guidelines.