National environmental standard for PM10 – number of times it is exceeded
Monitoring the number of times the national environmental standard for PM10 is exceeded provides an understanding of how frequently people are being exposed to poor air quality.
The national environmental standard for PM10 is exceeded whenever daily monitoring shows PM10 levels in an airshed are above the standard of 50 μg/m3.
A breach of the national environmental standard occurs when the PM10 standard of 50 μg/m3 is exceeded more than once in a year. Airsheds that exceed the standard zero times or only once a year, do not breach the PM10 standard.
Current situation
In 2010, 15 airsheds did not exceed the standard on any day throughout the year. Seven airsheds exceeded the standard on only one day throughout the year, which is allowed under the national environmental standard for PM10.
Twenty-two airsheds (50 per cent) exceeded the standard on two or more days, therefore breaching the PM10 standard. Approximately 18 per cent of New Zealand’s population lives in these breaching airsheds.
The three airsheds that exceeded the standard most often in 2010 were Otago 1 (76 exceedances), followed by Timaru (49) and Otago 2 (47). Each exceedance represents a day when the PM10 level is above the PM10 standard.
In New Zealand, the PM10 standard is most often exceeded during the winter months when burning solid fuels for home heating is at its peak and winter temperature inversions (still, cold conditions that restrict the dispersion of pollutants) are most common.
Number of times airsheds exceeded the PM10 standard in 2010
Read table of data of this graph
| North Island airsheds | South Island Airsheds | ||
|---|---|---|---|
| Auckland | 1 | Ashburton | 11 |
| Hamilton City | 0 | Blenheim | 2 |
| Hastings | 15 | Christchurch | 16 |
| Helensville | 0 | Geraldine | 4 |
| Kaitaia | 0 | Gore | 2 |
| Kumeu | 0 | Invercargill | 35 |
| Lower Hutt | 0 | Kaiapoi | 23 |
| Matamata | 0 | Nelson A | 7 |
| Napier | 3 | Nelson B | 1 |
| Ngaruawahia | 0 | Otago 1 | 76 |
| Porirua | 0 | Otago 2 | 47 |
| Putaruru | 1 | Otago 3 | 14 |
| Rotorua | 16 | Otago 4 | 1 |
| Taihape | 0 | Rangiora | 13 |
| Taumarunui | 1 | Reefton | 22 |
| Taupo | 1 | Richmond | 7 |
| Te Kuiti | 3 | Timaru | 49 |
| Tokoroa | 16 | Waimate | 9 |
| Turangi | 0 | ||
| Upper Hutt | 0 | ||
| Waiheke Island | 0 | ||
| Waihi | 0 | ||
| Wainuiomata | 1 | ||
| Wairarapa | 4 | ||
| Wellington | 0 | ||
| Whangarei | 0 | ||
Data sources: Auckland Council, Bay of Plenty Regional Council, Environment Canterbury, Environment Southland, Greater Wellington Regional Council, Hawke’s Bay Regional Council, Horizons Regional Council, Marlborough District Council, Nelson City Council, Northland Regional Council, Otago Regional Council, Tasman District Council, Waikato Regional Council, West Coast Regional Council.
Trend
In 2010, the highest number of exceedances in one airshed was 76, down from 91 in 2008 (but up from 51 in 2005 and 2006, 55 in 2007, and 60 in 2009).
Note that meteorological variation can affect air quality monitoring results from year-to-year and may have influenced this trend.
The airsheds recording the highest number of exceedances from 2005 to 2010 remained fairly consistent. Four airsheds – Christchurch, Kaiapoi, Otago 1, and Timaru – consistently appeared in the top 10 list from 2005 to 2010. For the first time since 2005, Nelson A and Richmond airsheds are not on the top 10 list.
Top 10 airsheds exceeding the standard, 2005-2010
| Rank | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
|---|---|---|---|---|---|---|
| 1 | Nelson A (51) | Nelson A (51) | Otago 1(2) (55) | Otago 1(2) (91) | Otago 1(2) (60) | Otago 1(2) (76) |
| 2 | Timaru (46) | Otago 1(2) (50) | Timaru (36) | Otago 2(3) (46) | Timaru (38) | Timaru (49) |
| 3 | Otago 1(2) (42) | Richmond (37) | Rotorua (29) | Rotorua (39) | Otago 2(3) (35) | Otago 2(3) (47) |
| 4 | Richmond (34) | Timaru (36) | Nelson A (26) | Timaru (37) | Nelson A (34) | Invercargill (35) |
| 5 | Tokoroa (33) | Kaiapoi (28) | Reefton (24) | Hastings (28) | Rotorua (27) | Kaiapoi (23) |
| 6 | Christchurch (32) | Christchurch (27) | Richmond (21) | Nelson A (25) | Kaiapoi (23) | Reefton (22) |
| 7 | Ashburton (18) | Ashburton (26) | Kaiapoi (20) | Richmond (20) | Richmond (21) | Christchurch (16) |
| 8 | Hastings (18) | Nelson B (24) | Christchurch (14) | Kaiapoi (19) | Tokoroa (17) | Rotorua (16) |
| 9 | Kaiapoi (17) | Rotorua (23) | Ashburton (13) | Christchurch (18) | Reefton (16) | Tokoroa (16) |
| 10 | Nelson B (13) | Hastings (18) | Hastings (13) | Reefton (17) | Christchurch (13) | Hastings (15) |
Notes:
- The number in brackets after each airshed is the number of exceedances in the airshed.
- From 2006, Otago 1 monitoring results are the combination of Alexandra and Arrowtown results. From 2008, Clyde and Cromwell results are also included in the Otago 1 monitoring results.
- From 2008, Otago 2 monitoring results are the combination of Mosgiel and Milton. Before 2008, the results are from Mosgiel only.
Trends in exceedances
The average number of exceedances experienced per New Zealander per year has been used as an index for air quality at a national level. The index provides a concise and high level overview of the trend of New Zealand’s air quality by distilling a more complex set of information. It is important to note that this index does not replace the more detailed and localised assessment of air quality at the airshed level.
This index indicates that air quality was at its worst in 2001, and has improved steadily since 2006. More information about how this index was created can be found in the Further information section.
National air quality exceedances per person, 2000-2010
Read table of data of this graph
| Year | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Index value | 4.8 | 7.8 | 4.4 | 4.8 | 4.6 | 5.8 | 5.6 | 4.0 | 4.6 | 3.8 | 3.5 |
Data sources: Auckland Council, Bay of Plenty Regional Council, Environment Canterbury, Environment Southland, Greater Wellington Regional Council, Hawke's Bay Regional Council, Horizons Regional Council, Marlborough District Council, Nelson City Council, Northland Regional Council, Otago Regional Council, Tasman District Council, Waikato Regional Council, West Coast Regional Council.
Move to information on peak daily levels.
Last updated: 2 August 2011
