Other air pollutants
This section provides data on three air pollutants at monitoring stations in Aotearoa New Zealand
- nitrogen dioxide (NO2)
- sulphur dioxide (SO2)
- carbon monoxide (CO)
These air pollutants can cause a range of health effects, including respiratory problems. Air quality standards and guidelines have been developed to provide some level of protection against health risks.
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About nitrogen dioxide
Nitrogen dioxide (NO2) is a corrosive gas that mixes with the air. In New Zealand, most human-made forms of NO2 come from motor vehicles.
Exposure to NO2 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. In 2016, NO2 was responsible for 61% of the social cost of air pollution in New Zealand, in terms of the direct cost to the health system as well as the loss of life, lost quality of life and lost productivity.
In 2016, human-made NO2 was responsible for:
- 2,025 premature deaths (in people aged 30+ years)
- 8,531 hospitalisations for cardiovascular and respiratory disease, including 845 hospitalisations for childhood asthma
- 13,229 cases of childhood asthma.
- $9.4 billion in social costs.
About sulphur dioxide
Sulphur dioxide (SO2) is a colourless gas that has a strong smell. It is produced from the combustion of sulphur-containing fuels such as coal and oil, such as are used in electricity generation or shipping. Other industrial activities such as aluminium production and fertiliser manufacturing are also a source of SO2. Sulphur dioxide easily reacts with other substances (e.g. water) to form harmful compounds such as sulphuric acids; it can also react with other air pollutants to form smaller, more harmful
particles or create poor visibility.
SO2 exposure is associated with respiratory problems such as bronchitis and hospital admissions due to asthma. Children, asthmatics, and people with chronic lung disease are most at risk of developing these health problems (WHO 2013).
About carbon monoxide
Carbon monoxide (CO) is a colourless, odourless gas formed by incomplete combustion of fuels such as petrol (from motor vehicles), wood and coal (from home heating and industry) and gases (such as those used in gas stoves and heaters). Carbon monoxide can pass into the bloodstream, where it 'saturates' the blood in the place of oxygen molecules, preventing the blood from absorbing oxygen from the lungs. Carbon monoxide poisoning can have adverse effects on the brain, heart and general health and in some cases can be fatal. Unborn babies, and middle-aged or elderly people with heart disease are most vulnerable to carbon monoxide, particularly if they live in locations with limited airflow where CO is able to accumulate.
Information about the data
Nitrogen dioxide
Monitoring sites exceeding the national environmental standard (one-hour average) for nitrogen dioxide
One-hour average nitrogen dioxide concentration data comes from the Ministry for the Environment and Stats NZ (Ministry for the Environment and Stats NZ 2021) as part of New Zealand’s Environmental Reporting Series. One-hour average nitrogen dioxide concentrations (in µg/m3) are compared with the National Environmental Standard for Air Quality for nitrogen dioxide. The threshold is exceeded when concentrations are above 200µg/m3. Nine exceedances in a 12-month period are allowed.
Monitoring sites exceeding the WHO average guidelines for nitrogen dioxide
Using the same data source as above, EHINZ calculates 24-hour and 12-month averages from the hourly data and these are measured against the WHO guideline limits. Exceedances occur when concentrations are above 25µg/m3 for daily concentrations or 10µg/m3 for annual concentrations. For additional information, see the metadata link below.
Carbon monoxide
Carbon monoxide concentrations can be measured against the following limits and guidelines:
- The New Zealand national environmental standard for carbon monoxide is 10 mg/m3 as an 8-hour moving average (one exceedance of the limit is allowed per year).
- The New Zealand national ambient air quality guideline for carbon monoxide is 10 mg/m3 as a 1-hour average.
- The WHO 2021 air quality guideline for daily (24-hour) average for carbon monoxide is 4mg/m3.
Data for CO concentrations is provided at hourly intervals; these measurements are an average of constant sampling over the course of that hour (Ministry for the Environment, 2009). The eight-hour rolling averages for the NESAQ exceedances are calculated based on these hourly averages by EHINZ after cleaning out invalid hourly data, e.g. negative concentrations, which imply a calibration error in the recording instrument. EHINZ also uses the hourly data to assess for exceedances of the WHO hourly guideline and the national ambient guideline.
Sulphur dioxide
Monitoring sites exceeding the national environmental standard (one-hour average) for sulphur dioxide
Hourly average SO2 concentration data comes from the Ministry for the Environment and Statistics NZ (Ministry for the Environment and Statistics NZ 2021) as part of New Zealand’s Environmental Reporting Series. These concentrations (in µg/m3) are compared with the National Environmental Standard for Air Quality for sulphur dioxide. The lower threshold is exceeded when concentrations exceed 350µg/m3 and the upper threshold is exceeded when concentrations are greater than 570µg/m3. The lower threshold can be exceeded nine times in a calendar year, whereas the upper threshold cannot be exceeded even once.
Monitoring sites exceeding the WHO daily guideline for sulphur dioxide
The one-hour average sulphur dioxide concentrations are used to calculate 24-hour averages, which are measured against the 2021 WHO daily average guideline. Exceedances occur when concentrations are above 40µg/m3.
References 
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 and Statistics NZ. 2021. Our Air 2021. 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.
4. WHO. 2021. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. Bonn: WHO European Centre for Environment and Health
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