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Air Quality (Particulate Matter – PM₁₀)

• At a glance
• Introduction
• About this report card
• Peak daily PM₁₀ levels
• Annual exceedences of the standard
• NZ annual guideline for PM
• Case study
• Future watch
• Further information
• Technical notes

Air Quality (Particulate Matter – PM₁₀)

At a glance

Poor outdoor air quality is a significant issue in some locations in New Zealand. About two-thirds of New Zealanders live in areas that can experience air pollution. Each year, about 1100 people die prematurely from air pollution in urban areas. Most poor air quality in New Zealand is caused by high winter levels of particulate matter (known as PM₁₀) from wood and coal used for home heating. Auckland, where about a third of New Zealand’s population lives, also experiences high levels of PM₁₀ from road transport.

By tracking air quality against a national standard, which sets an acceptable daily level for PM₁₀, and the New Zealand guideline, which sets an acceptable annual level, we can understand more about our changing air quality and how this might affect our health. Regional councils currently monitor 40 areas where air quality is likely to or known to breach the PM₁₀ standard – these areas are known as airsheds. In most cases, airsheds are single towns or cities, though some group a number of towns together.

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National environmental standard for PM₁₀

COMPLIANCE WITH THE STANDARD: In 2007, 42 per cent of New Zealand’s monitored airsheds complied with the national standard for PM₁₀.

Getting better

While there has been some fluctuation, compliance with the national standard has increased from 31 per cent in 2005. However, 18 of the 20 non-complying airsheds in 2005 have continued to breach the PM₁₀ standard.

Getting worse

ANNUAL EXCEEDENCES OF THE STANDARD: In 2007, the Otago 1, Timaru and Rotorua airsheds breached the PM₁₀ standard most often. The highest number of exceedences in an airshed increased from 51 in 2005 to 55 in 2007.

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New Zealand annual guideline for PM₁₀

In 2007, 81 per cent of the 37 airsheds for which data was reported met the New Zealand annual guideline for PM₁₀. The seven airsheds which did not meet the guideline were Nelson B, Timaru, Kaiapoi, Nelson A, Reefton, Rotorua and Richmond.

Getting better

In the decade to 2007, indicator sites in Auckland, Hamilton and Wellington consistently met the New Zealand annual guideline, while Christchurch and Dunedin sites commonly exceeded it. For the first time since reporting began, indicator sites in all five main centres met the guideline in 2007.

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International comparison

In 2006, annual levels of PM₁₀ at indicator sites in New Zealand’s five main centres were comparable to levels at similar sites in Sydney and Melbourne.

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Future watch

Regional councils are required to bring PM₁₀ levels in their airsheds to within the national standard by 2013. Regional councils will not be able to grant resource consent applications for discharges to air in airsheds that fail to comply with the PM₁₀ standard after 2013.

To date, there has been fluctuation in compliance with the national environmental standard. This is because weather is an important influence on air quality. Yearly weather patterns will continue to be reflected in the PM₁₀ levels, and therefore we can expect to see further fluctuation in compliance in the future.

Introduction

Clean air contributes to New Zealand’s quality of life – not only people’s health, but also the beauty of the natural and physical environment (Ministry for the Environment, 2007).

New Zealand has good air quality in most locations for most of the time (Ministry for the Environment, 2007). However, solid fuel (wood and coal) used for home heating and exhaust emissions from transport can affect air quality in about 30 locations, particularly during winter (Ministry for the Environment, unpublished a). Each year, about 1100 New Zealanders die prematurely from air pollution in urban areas (Fisher et al, 2007). Air pollution from households is a significant factor, with more than half of all bronchitis cases, and acute respiratory and cardiac hospitalisations in 2001 associated with the use of wood and coal for home heating (Fisher et al, 2007).

A number of air pollutants can affect the quality of air we breathe. Particulate matter is a collective term used to describe very small solid or liquid particles in the air, such as dust, smoke or fog. A pollutant of particular concern in New Zealand is PM₁₀ (see text box 1).

Most PM₁₀ in New Zealand comes from burning solid fuels for home heating. This, along with the more frequent settled weather conditions during winter, is why most peak PM₁₀ levels occur during this time of year. Exhaust emissions from vehicles are another significant source of PM₁₀ in cities like Auckland. It is estimated that the number of New Zealanders that die prematurely from traffic-related air pollution is similar to the number killed in road traffic accidents (Fisher et al, 2002). Industry, as well as natural sources such as pollen, mineral dust and sea salt, can also contribute to PM₁₀ levels.

National air quality standards and guidelines

In 2004, national environmental standards (NES) for air quality were introduced in New Zealand to provide a guaranteed level of protection for the health of New Zealanders (Ministry for the Environment, 2005a). The daily level set for PM₁₀ is 50 micrograms per cubic metre (µg/m³) as a 24-hour average (midnight to midnight). To comply with the standard, this level can not be exceeded more than one day each year.

A national air quality guideline was put in place in 2002 to set an acceptable annual average level of PM₁₀ (20 µg/m³). The guideline represents the minimum standard that outdoor air quality should meet in order to protect human health and the environment (Ministry for the Environment, 2002).

Managed airsheds

Following the introduction of the national environmental standard, 68 areas were identified in New Zealand where air quality is likely or known to breach the PM₁₀ standard – these areas are known as airsheds. Some airsheds are also identified based on factors such as: the number of people living in the airshed, its unique weather patterns and geography, or because local air emissions (eg, local industrial activity) need to be managed separately. In most cases, airsheds are towns or cities, though in some areas they may include a number of towns – for example, the Otago 1 airshed combines both Alexandra and Arrowtown. As of 2007, 40 of New Zealand’s 68 airsheds are being monitored. Not all airsheds are monitored: if exploratory tests show that PM₁₀ levels are above the standard or a high number of people are affected, then ongoing monitoring is required.

To date, approximately 1.5 per cent of New Zealand’s total land area has been gazetted as an airshed. This equates to an area in which an estimated two-thirds of New Zealand’s population live (Ministry for the Environment, unpublished b). Areas outside airsheds are generally sparsely populated, and, as a result, little PM₁₀ monitoring occurs in the rural environment and areas free from emissions caused by human activity (Ministry for the Environment, 2007).

About this report card

This environmental report card discusses peak PM₁₀ levels and annual levels for PM₁₀ in monitored airsheds in New Zealand. It compares these with the national standard for PM₁₀ and the New Zealand air quality guideline. The report card also reviews the number of times the standard is exceeded.
This report card looks at:

• national environmental standard for PM₁₀ – peak daily levels
• national environmental standard for PM₁₀ – number of times it is exceeded
• New Zealand annual guideline for PM₁₀.

Key findings

National environmental standard for PM₁₀ – peak daily levels

This section reports the daily levels of PM₁₀ in the 40 monitored airsheds in New Zealand against the national environmental standard, which sets an acceptable daily level for PM₁₀. Reporting peak daily levels of PM₁₀ provides an important short-term snapshot of air quality in an airshed. It allows us to understand the intensity of air pollution to which people are being exposed.

Current situation

The national environmental standard sets an acceptable daily level for PM₁₀, and requires continuous monitoring throughout the year in areas where PM₁₀ is likely to breach the standard. Forty airsheds were monitored in New Zealand in 2007. Of these, 17 airsheds (42 per cent) complied with the PM₁₀ standard.

Figure 2 shows that 13 of the 40 monitored airsheds (32 per cent) had a peak daily level below the standard of 50 µg/m³. Each airshed is allowed to exceed the standard once a year (see text box 3), which is why four airsheds with peak daily levels greater than 50 µg/m³ still complied with the standard. In 2007, on average, South Island peak daily levels, shown on the right hand side of figure 2 [figure 2 shows a bar graph with North Island airsheds on the left and South Island airsheds on the right], were higher than North Island levels. Eight of the 10 airsheds that recorded the highest daily PM₁₀ levels in New Zealand are located in the South Island. Levels ranged from 104 to 168 µg/m³, with the three highest levels recorded in the Otago 1, Auckland and Reefton airsheds.

Figure 2
Highest 24-hour PM₁₀ concentration in New Zealand airsheds, 2007

Text description of figure 2.
Notes:
(1) From 2006, Otago 1 monitoring results are the combination of Alexandra and Arrowtown results.
(2) See below for data sources.

Trend

Since we last reported on PM₁₀ in Environment New Zealand 2007, there has been an increase in the number of monitored airsheds in New Zealand. Figure 3 shows an annual summary of compliance with the PM₁₀ standard. The proportion of complying airsheds decreased in 2006, with half of the newly monitored airsheds breaching the standard, as shown in table 1. After complying in 2005, the Hamilton, Otago 3 (Dunedin) and Wairarapa airsheds breached the standard in 2006.

The following year, five of the seven newly monitored airsheds complied with the standard. This, together with the Gore, Hamilton, Waimate and Wairarapa airsheds, contributed to the increased proportion of complying airsheds in 2007.

Seventeen of the 40 monitored airsheds (42 per cent) complied with the PM₁₀ standard in 2007. The highest recorded daily PM₁₀ level also showed an improving trend by dropping from 198 µg/m³ (Invercargill) in 2005, to 168 µg/m³ (Otago 1) in 2007.

Figure 3
Summary of compliance with the PM₁₀ standard in New Zealand

Text description of figure 3.

Data sources for figures 2 and 3: Auckland Regional Council, unpublished; Environment Bay of Plenty, unpublished; Environment Canterbury, unpublished; Environment Southland, unpublished; Environment Waikato, unpublished; Greater Wellington Regional Council, unpublished; Hawke’s Bay Regional Council, unpublished; Horizons Regional Council, unpublished; Marlborough District Council, unpublished; Nelson City Council, unpublished; Northland Regional Council, unpublished; Otago Regional Council, unpublished; Tasman District Council, unpublished; West Coast Regional Council, unpublished.

Note: From 2006, Otago 1 monitoring results are the combination of Alexandra and Arrowtown results. In 2006, four additional airsheds were monitored, and in 2007, seven additional airsheds were monitored.

However, 18 of the 20 breaching airsheds in 2005 have continued to breach the PM₁₀ standard (see table 1). Six of these airsheds – Christchurch, Kaiapoi, Nelson A, Otago 1, Rangiora and Timaru – are among the 10 airsheds recording the highest daily PM₁₀ levels from 2005 to 2007 (see table 2). These airsheds are expected to have difficulty in complying with the PM₁₀ standard by 2013 (see the Future watch section). Only six airsheds have consistently complied with the PM₁₀ standard between 2005 and 2007 – Kaitaia, Lower Hutt, Upper Hutt, Wainuiomata, Wellington and Whangarei.

Note: From 2006, Otago 1 monitoring results are the combination of Alexandra and Arrowtown results.

Key findings

National environmental standard for PM₁₀ – number of times it is exceeded

This section reports on how many times the national standard for PM₁₀ is exceeded over a year in the 40 monitored airsheds in New Zealand. Monitoring this allows us to understand how frequently people are being exposed to poor air quality.

Current situation

In 2007, 13 airsheds (32 per cent) did not exceed the national standard at all. Eleven of these are in the North Island, as shown in the left hand side of figure 5. The airsheds that exceeded the standard most often in 2007 include the Otago 1 airshed (55 instances), followed by Timaru (36) and Rotorua (29). Each instance represents a day when PM₁₀ levels are above the standard. The greater the number, the more days that PM₁₀ levels are at a level that could affect people’s health.

In New Zealand, the PM₁₀ standard and peak levels are more often exceeded during the winter months when burning solid fuels for home heating is at its peak and winter inversions are most common (see text box 4).

Figure 5
Number of times New Zealand airsheds exceeded the PM₁₀ standard, 2007

Text description of figure 5.
Data sources: Auckland Regional Council, unpublished; Environment Bay of Plenty, unpublished; Environment Canterbury, unpublished; Environment Southland, unpublished; Environment Waikato, unpublished; Greater Wellington Regional Council, unpublished; Hawke’s Bay Regional Council, unpublished; Horizons Regional Council, unpublished; Marlborough District Council, unpublished; Nelson City Council, unpublished; Northland Regional Council, unpublished; Otago Regional Council, unpublished; Tasman District Council, unpublished; West Coast Regional Council, unpublished.

Trend

The highest number of times a single airshed exceeded the national standard increased to 55 in 2007, up from 51 in 2005 and 2006. As shown in table 3, the highest number was recorded in the Otago 1 airshed in 2007, which reports monitoring results from both Alexandra and Arrowtown.

The airsheds recording the highest number of instances from 2005 to 2007 remained fairly consistent. Eight airsheds – Ashburton, Christchurch, Hastings, Kaiapoi, Nelson A, Otago 1, Richmond and Timaru – consistently appeared in the top 10 list from 2005 to 2007.

Of these eight airsheds, seven are in the South Island. A recent study of home heating fuels used in 29 New Zealand towns showed the rate of household coal use in 20 South Island towns was more than double the national average (Ministry for the Environment, 2005b). Coal fires emit 58–75 per cent more PM₁₀ pollution than even the least efficient wood burner (Ministry for the Environment, 2005c). This, together with the occurrence of temperature inversions (see figure 4) and generally lower winter temperatures in the South Island, may contribute to higher PM₁₀ levels and number of times South Island airsheds exceed the standard.

Note: From 2006, Otago 1 monitoring results are the combination of Alexandra and Arrowtown results.

Key findings

New Zealand annual guideline for PM₁₀

This section reports on the average annual level of PM₁₀ compared to the New Zealand guideline, a health-based guideline which sets an acceptable annual level for PM₁₀. Annual averages take into account both peak and low pollution periods in an airshed, giving an important long-term picture of air quality.

Current situation

In 2007, 37 of the 40 monitored airsheds were able to report an annual average for PM₁₀. A minimum of 75 per cent data capture rate is recommended for an airshed to be able to report an annual average, and three airsheds were not able to achieve this. Thirty of the 37 airsheds (81 per cent) met the New Zealand annual air quality guideline for PM₁₀ (20 µg/m³). The seven airsheds that did not meet the guideline were Nelson B, Timaru (23 µg/m³); Kaiapoi, Nelson A, Reefton, Rotorua (22 µg/m³); and Richmond (21 µg/m³).

Some airsheds can significantly breach the national standard for PM₁₀, while the annual average in that airshed meets the guideline. To illustrate this, while Otago 1 airshed had the highest daily PM₁₀ level and exceeded the standard the most times in 2007, the annual average in the airshed still met the annual guideline that year. This would suggest that PM₁₀ levels in the Otago 1 airshed are generally low outside the peak winter pollution period.

Long-term trend

In the decade to 2007, PM₁₀ levels at one indicator site in Auckland, Hamilton and Wellington consistently met the annual guideline (see figure 6). While the levels at the Christchurch and Dunedin sites commonly exceeded the guideline over this period, for the first time since monitoring began, in 2007 each indicator site in the five main centres met the annual guideline.

Short-term trend

Annual average PM₁₀ levels have fluctuated since we last reported them in Environment New Zealand 2007. In 2006, there was an increase in annual average PM₁₀ levels at all the indicator sites in the five main centres except Hamilton. However, in 2007 there was a drop in PM₁₀ levels in Hamilton, Christchurch and Dunedin. Levels in Auckland remained the same. Annual average data for 2006 and 2007 is shown in figure 6.

Figure 6
Annual average PM₁₀ levels at indicator sites in the five main centres of population

Text description of figure 6.
Note: *Data capture for these years is less than 50 per cent.

Data sources: Auckland Regional Council, unpublished; Environment Canterbury, unpublished; Environment Waikato, unpublished; Greater Wellington Regional Council, unpublished; Otago Regional Council, unpublished.

International comparison

Outdoor air quality is very site-specific. It is therefore reasonable to compare air quality at particular sites in different countries, but not to compare country averages (Ministry of Social Development, 2008).

In 2006, the average annual levels of PM₁₀ at indicator sites in each of the five main New Zealand centres – Auckland, Hamilton, Wellington, Christchurch and Dunedin – were similar to levels at 20 similar sites in the Australian regions of Sydney and Port Phillip (which includes Melbourne). The New Zealand sites had average annual levels of PM₁₀ ranging from 12–25 µg/m³, while the sites in the two Australian regions had average annual PM₁₀ levels ranging from 14–26 µg/m³ (Department of Environment and Climate Change, New South Wales Government, 2008; Environment Protection Authority Victoria, 2008).

Temperature inversion trapping air pollution from winter home heating, Cromwell

Source: Otago Regional Council.

Case study

Future watch

Under the national environmental standard, by September 2013 regional councils are required to bring the PM₁₀ levels of their airsheds within the PM₁₀ standard of 50 µg/m³. Councils cannot grant resource consent applications for discharges to air in airsheds that fail to comply with the PM₁₀ standard after that date.

Between 2005 and 2007, the number of complying airsheds has fluctuated. We can expect to see further fluctuation in compliance over the next five years to September 2013. This is because weather is an important influence on air quality and expected fluctuations in yearly weather patterns will most likely be reflected in the PM₁₀ levels.

Another aspect to compliance involves costs associated with replacing old, non-compliant wood burners with burners that comply with the national environment standard, or other cleaner home heating options. This is a major part of regional council action plans to reduce PM₁₀ levels in an airshed. Funding programmes are in place in some regions, but in most, homeowners will still need to cover at least part of the cost of improving air quality in their airsheds. As New Zealand heads into recession, it is not clear whether homeowners will continue to prioritise spending money on a shift to cleaner heating. This increases the risk that some airsheds may not comply with the PM₁₀ standard by September 2013.

The Vehicle Exhaust Emissions Rule, which took effect at the beginning of 2008, is one initiative expected to improve the harmful exhaust emissions of used imported vehicles. As a result, this rule is also expected to help reduce the health-related effects of vehicle exhaust emissions, particularly in cities such as Auckland.

Further information

The implementation of the national environmental standards for air quality is a major step in addressing air pollution in New Zealand. Information about it can be found on the Ministry for the Environment’s website at: www.mfe.govt.nz/laws/standards/air-quality-standards.html and www.mfe.govt.nz/publications/rma/user-guide-draft-oct05/index.html

More information on New Zealand’s air quality can be found in the Air chapter of Environment New Zealand 2007 at: www.mfe.govt.nz/publications/ser/enz07-dec07/chapter-7.pdf (PDF, 870 KB).

Home heating is the most common source of PM₁₀ air pollution in New Zealand. Switching to cleaner, more efficient wood burners can significantly reduce pollution levels. A well-insulated house needs less heating, so having proper insulation in your home is another important element of reducing air pollution. For further information on changing your existing wood burner, installing a new one, or adding insulation to your home, visit the following websites:

• www.eeca.govt.nz
• www.energywise.govt.nz
• www.cleanheat.org.nz
• www.mfe.govt.nz/laws/standards/woodburners/authorised-woodburners.html

Car owners can obtain more information on how to reduce vehicle exhaust emissions at: http://www.transport.govt.nz/legislation/ChoketheSmoke/ 

Technical notes

Limitations of this indicator

Health impacts of air quality

The national environmental indicator discussed in this report card is primarily focused on tracking air quality against the national environmental standard for PM₁₀. Although localised studies on air quality are able to provide more detailed information on the human health effects of air pollution, this indicator does not report on or quantify the specific human health effects of poor air quality at the national scale.

Furthermore, the indicator does not show the effects from exposure to two or more air pollutants in the environment. This is relevant because most combustion processes give rise to several pollutants simultaneously (Ministry for the Environment, 2007).

Variations in weather and climate

The indicator reports on the state of air quality over time, but does not allow for the influence of variations in weather and climate from year to year. This makes it difficult to assess whether changes in air quality are caused by changing environmental pressures – for example, a reduction in the emission of air pollutants – or meteorological variations, such as changes in wind patterns (Ministry for the Environment, 2007).

References

Auckland Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Department of Environment and Climate Change, New South Wales Government. 2008. Quarterly Air Monitoring Reports. Retrieved from www.environment.nsw.gov.au/air/datareports.htm#quarterlies (December 2008).

Environment Bay of Plenty. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Environment Canterbury. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Environment Protection Authority Victoria. 2008. Victoria’s Air Quality 2006: Air Monitoring Data Tables. Retrieved from www.epa.vic.gov.au/air/monitoring/air_monitoring_report_2006.asp (December 2008).

Environment Southland. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Environment Waikato. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Fisher G, Kjellstrom T, Kingham S, Hales S, Shresta R. 2007. Health and Air Pollution in New Zealand: Main Report. Wellington: Health Research Council of New Zealand, Ministry for the Environment and Ministry of Transport.

Fisher GW, Rolfe KA, Kjellstrom T, Woodward A, Hales S, Sturmam AP, Kingham S, Petersen J, Shrestha R, King D. 2002. Health Effects Due to Motor Vehicle Air Pollution in New Zealand. Retrieved from www.transport.govt.nz/assets/PDFs/health-effects-of-vehicle-emissions.pdf (27 November 2008). [This document is now at www.transport.govt.nz/research/Documents/health-effects-of-vehicle-emissions.pdf (PDF, 684 KB), updated 4 March 2009]

Greater Wellington Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Hawke’s Bay Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Horizons Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Marlborough District Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Ministry for the Environment. 2002. Ambient Air Quality Guidelines. Wellington: Ministry for the Environment.

Ministry for the Environment. 2003. Health Effects of PM₁₀ in New Zealand. Wellington: Ministry for the Environment.

Ministry for the Environment. 2005a. Updated Guide to Resource Management (NES Relating to Certain Air Pollutants, Dioxins and Other Toxics) Regulations 2004 Including Amendments 2005. Wellington: Ministry for the Environment.

Ministry for the Environment. 2005b. Warm Homes Technical Report: Home Heating Methods and Fuels in New Zealand. Wellington: Ministry for the Environment.

Ministry for the Environment. 2005c. Warm Homes Technical Report: Detailed Study of Heating Options in New Zealand: Phase 1 Report. Wellington: Ministry for the Environment.

Ministry for the Environment. 2007. Environment New Zealand 2007. Wellington: Ministry for the Environment.

Ministry for the Environment. 2008. Air Particles. Retrieved from www.mfe.govt.nz/issues/air/breathe/particles.html (October 2008).

Ministry for the Environment. Unpublished a. Highest 24-hour PM₁₀ Concentrations in New Zealand Airsheds (2007). Table compiled from regional council data for the purpose of this environmental report card.

Ministry for the Environment. Unpublished b. Table of Land Area and Population in New Zealand Airsheds.

Ministry of Social Development. 2008. The Social Report 2008. Wellington: Ministry of Social Development.

Nelson City Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Northland Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Otago Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005-2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

Tasman District Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.

West Coast Regional Council. Unpublished. Particulate Matter (PM₁₀) Data (2005–2007). Data provided to the Ministry for the Environment for the purpose of this environmental report card.