Nitrogen dioxide

Traffic-related air pollution is measured across the region by a network of low cost nitrogen dioxide (NO₂) passive diffusion tubes. (A picture of NO₂ tube site can be seen here). Air pollution levels from traffic vary considerably across the region and so a larger monitoring network is needed to capture representative regional and local trends. Some sites are also part of NZTA’s national monitoring network. The passive tubes are a manual method and data is only available as monthly averages after the tube has been analysed in the lab.

Core sites

Benchmarking & Resources has more information on the guidelines and standards used for the following summary tabs.

Annual summary

The map shows annual average NO₂ (μg/m³) from core monitoring sites across the region. The table also shows the annual summary for NO₂ reported as a 24-hour average and as a 1-hour average from core monitoring sites across the region. The national standard allows nine 1-hour averages per year to be higher than 200 μg/m³ (10^th highest value). The national guideline is a maximum 24-hour average of 200 μg/m³. The World Health Organization guideline is 40 μg/m³.

Drag and scroll on the map to move and zoom in on areas of interest.
Hover on the site circles to see more information.
Use the selection box ( ) to subset the map and table data to that area.
Click on sites in the table to highlight them on the map.
Use the arrows ( ↓↑ ) next to the table headers to sort the data.

All values in μg/m³. Data capture (%) refers to the proportion of total hours with at least 45 minutes of data present and the proportion of total days with at least 18 hours of data present.

24-hour averages

The graphs show 24-hour average nitrogen dioxide levels from core monitoring sites. The colour bands show nitrogen dioxide levels relative to a percentage of the national guideline which is 100 μg/m³. The regional target is 66 μg/m³ or lower which is based on air quality being maintained at the ‘acceptable’ or better category which corresponds to no more than 66% of the national guideline (green to dark blue). Hover over the graphed days for specific values.

Trends annual average

The graphs show trends in annual average nitrogen dioxide levels from core monitoring sites. The colour bands show nitrogen dioxide levels relative to a percentage of the World Health Organization guideline which is 40 μg/m³ - from green (less than 10% of the standard) to red (more than 100% of the standard). Hover over the graphed years for specific values.

Note only previous years with at least 75% data capture (ie, 274 days with data present) are shown.

Passive tube sites

The map shows annual average NO₂ (μg/m³) from the traffic-related passive tube monitoring sites across the region. The World Health Organization guideline is 40 μg/m³. Results cannot be used for assessing compliance against the guideline as the passive diffusion tubes are not a standard method and may overestimate concentrations.

The table shows seasonal averages based on NZTA reporting criteria for summer (January to March) and winter (July to September). NO₂ levels are generally higher in winter than in summer most likely because the colder temperatures and lower wind speeds during winter are less favourable for dispersing vehicle emissions.

Drag and scroll on the map to move and zoom in on areas of interest.
Hover on the site circles to see more information.
Use the selection box ( ) to subset the map and table data to that area.
Click on sites in the table to highlight them on the map.
Use the arrows ( ↓↑ ) next to the table headers to sort the data.

All values in μg/m³. Data capture (%) refers to the proportion of total months with data present per year. Toggle between tabs to see summaries at NZTA ID (site) level or aggregated by site type. See benchmarking & resources for more information on each site type.