Most sites were likely to meet the nitrogen dioxide guidelines in 2013
In 2013, most monitoring sites were likely to meet the World Health Organization (WHO) annual average guideline for nitrogen dioxide (40 µg/m³) (118 out of 122 sites). The monitoring sites likely to exceed the guidelines were close to state highways and busy local roads .
Council monitoring data shows nitrogen dioxide concentrations in Auckland and Wellington have generally improved over time (Figure 1).
Figure 1: Annual average nitrogen dioxide concentration (µg/m³)
Nitrogen dioxide has been linked to increases in asthma symptoms, and reduced lung development and function in children. Nitrogen dioxide can also make people more susceptible to infections.
Six out of nine monitoring sites exceeded the daily WHO guideline for SO₂ between 2008 and 2017
Monitoring sulphur dioxide is important, as it is associated with respiratory illnesses such as bronchitis. People with asthma or other chronic lung problems are particularly at risk .
Four (out of nine) monitoring sites exceeded the lower 350µg/m3 threshold of the national one-hour average standard between 2008 and 2017 (Figure 2):
- Woolston (Christchurch)
- Port of Auckland (Auckland)
- Totara St (Mount Maunganui)
- Whareroa Marae (Mount Maunganui)
None of the stations exceeded this threshold more than the allowed 9 times in a 12-month period.
Figure 2: Number of exceedances of the NESAQ’s lower threshold (350µg/m3, nine exceedances per 12-month period allowed), 2008-2017
Whareroa Marae (Mount Maunganui) and Woolston (Christchurch) exceeded the upper 570µg/m3 threshold of the national one-hour average standard twice each between 2008 and 2017). No exceedances of this threshold are allowed. Both sites are classified as industrial sites (i.e. close to industrial activities).
Six out of nine monitoring stations exceeded the 24-hour average WHO guideline of 20µg/m3 between 2008 and 2017 (Figure 3).
Totara St (Mount Maunganui), an industrial monitoring site, exceeded the guideline the most – 659 times between 2008 and 2017. Residential monitoring sites such as Timaru, St Albans (Christchurch) and Robert St (Whangarei) reported no exceedances.
Figure 3: Number of exceedances of WHO 24-hour average guideline (20µg/m3), 2008-2017
For more information about sulphur dioxide, please download the factsheet.
No breaches of carbon monoxide in 2013
Carbon monoxide levels at all 21 monitored sites met the national short-term (8-hour) standard (of 10 µg/m³) in New Zealand in 2013. Many of these sites were peak sites, suggesting that carbon monoxide levels are low elsewhere also.
Carbon monoxide can harm health, by reducing the blood’s ability to carry oxygen. People with certain types of heart disease are at increased risk.
Information about the data
Nitrogen dioxide and carbon monoxide
Source: Ministry for the Environment – New Zealand’s Environmental Reporting Series: Environment Aotearoa 2015
Definition: Number of monitoring sites exceeding the WHO long-term (annual) guidelines and national short-term standards for nitrogen dioxide, sulphur dioxide and carbon dioxide. Only selected monitoring stations measure these air pollutants.
Source: Ministry for the Environment and Stats NZ – New Zealand’s Environmental Reporting Series: Our air 2018. Data to 2017
Definition for indicator 'Monitoring sites exceeding the national environmental standard (one-hour average) for sulphur dioxide': One-hour average sulphur dioxide concentrations (in µg/m3) are compared with the National Environmental Standard for Air Quality for sulphur dioxide. The lower threshold is exceeded when concentrations are above 350µg/m3 and the upper threshold is exceeded when concentrations are above 570µg/m3. The lower threshold is allowed to be exceeded nine times in a 12-month period.
Definition for indicator 'Monitoring sites exceeding the WHO daily guideline for sulphur dioxide': 24-hour averages are calculated and measured against the WHO daily average guideline. Exceedances occur when concentrations are above 20µg/m3.
For more information on the National Environmental Standards for Air Quality, visit the Ministry for the Environment website.
1. Ministry for the Environment. 2011. 2011 User’s Guide to the revised National Environmental Standards for Air Quality. Updated 2014. Wellington: Ministry for the Environment.
2. Ministry for the Environment & Stats NZ. 2015. New Zealand's Environmental Reporting Series: Environment Aotearoa 2015. Wellington: Ministry for the Environment.
3. WHO. 2013. Review of evidence on health aspects of air pollution – REVIHAAP Project. Copenhagen: WHO Regional Office for Europe.