Indicator findings

In New Zealand and around the world, the most significant human health impacts from poor air quality are associated with exposure to particulate matter (PM) (Health Effects Institute, 2018). Particulate matter is a term used for a mixture of solid particles and liquid droplets found in the air (US EPA, 2021). This report refers to two types of particulate matter:

• PM₁₀: larger particles (but still small enough that they can be inhaled), 10 micrometres or less in diameter
• PM_2.5: finer particles, 2.5 micrometres or less in diameter. Because PM₁₀ includes all particles smaller than 10 micrometres, PM_2.5 is a subset of PM₁₀.

There is considerable evidence that inhaling PM is harmful to human health, especially when of smaller particle size, such as PM_2.5 and finer. PM_2.5 can be particularly harmful because these particles can become trapped in the small airways deep in the lungs. When particles are very fine (PM_0.1) they can enter the bloodstream and penetrate organs in the body (EFCA, 2019).

Short- and long-term exposure to PM, even at low levels, can lead to a range of health impacts especially in vulnerable people (the young, the elderly, and people with existing respiratory conditions). At the less-severe end, it can cause temporary and reversible effects such as shortness of breath, coughing, or chest pain. However, there is strong evidence of more severe effects, namely, illness and premature death from heart attacks, strokes, or emphysema (where the air sacs in the lungs are damaged). Exposure to PM can also cause lung cancer and exacerbate asthma. Studies point to possible links with diabetes and atherosclerosis (the accumulation of fat, cholesterol, and other substances on artery walls, reducing blood flow) as a result of increased inflammation caused by particulate matter (WHO, 2013).

Particulate matter emissions typically result from combustion (such as burning petrol, diesel, wood, or coal) and abrasion processes (such as brake and tyre wear or road dust). Combustion tends to create fine particles (PM_2.5), whereas abrasion generates coarser particles (PM₁₀). Particulate matter can also be generated through the reaction of gases in the atmosphere (referred to as secondary particulate matter), and a proportion of particulate matter is naturally occurring, for example, sea salt.

A study by Talbot et al, (2021a, b) found that during the COVID-19 lockdown (alert level 4) in 2020, PM₁₀ concentrations decreased by between 11.5 and 34.1 percent across New Zealand. As the restrictions eased, concentrations of PM₁₀ increased. The scale of increase was more significant in southern regions, perhaps because the burning of wood for home heating is more prevalent during the colder months.

Measurement and assessment

Regional councils and unitary authorities monitor PM₁₀ concentrations in their regions. Data from 46 sites for state and 48 for trends, located across 14 regions, were used in this report.

In New Zealand, short-term exposure to PM₁₀ is assessed against the National Environmental Standards for Air Quality (NESAQ), which allows for a 24-hour average of 50 micrograms per cubic metre (μg/m³) (one exceedance per year is permitted under the standard). Long-term exposure is assessed against the 2005 World Health Organization (WHO) annual average air quality guidelines (AQG) of 20 μg/m³.

We also assess against the more stringent AQGs that the WHO recommended in September 2021 for PM₁₀: a 24-hour average of 45 μg/m³ and an annual average of 15 μg/m³.

Trends were analysed for sites with at least six complete years of data. All trends were assessed at the 95 percent confidence level. Where a trend was ‘indeterminate’, there was not enough certainty to determine a trend direction.

Key findings

In the four-year period between 2017 and 2020:

National Environmental Standards for Air Quality (NESAQ)

• Twenty-four of 46 sites (52 percent) had at least two exceedances of the 24-hour PM₁₀ NESAQ (50 μg/m³) over a 12-month period. Most exceedances were at sites classified as residential.
• Arrowtown (at 30 days), Pomona Street (Invercargill) (12 days), and Anzac Square (Timaru) (12 days) had the highest number of average daily exceedances of the 24-hour PM₁₀ NESAQ per year.
• The majority of all exceedances (83 percent) recorded over this four-year period were in winter (June, July, August). Only a relatively small number (14 percent) were recorded in autumn (March, April, May).

World Health Organization (WHO)

2005 air quality guidelines

• Three of 46 sites (7 percent) were above the PM₁₀ annual 2005 WHO AQG (20 μg/m³) at least once over the four-year period. These sites were: Anzac Square (Timaru), Pomona Street (Invercargill), and Arrowtown.
• Anzac Square (Timaru) was most often above the PM₁₀ annual 2005 WHO AQG, in 2017, 2019, and 2020.

2021 air quality guidelines

• Thirty-five of 46 sites (76 percent) were above the PM₁₀ 24-hour 2021 AQG (45 μg/m³); most were at sites classified as residential.
• Arrowtown, Anzac Square (Timaru), and Pomona Street (Invercargill) were above the PM₁₀ 24-hour 2021 WHO AQG most often: 24–55, 15–25, and 6–23 days per year, respectively (figure 1).
• Twenty-two of 46 sites (48 percent) were above the PM₁₀ annual 2021 WHO AQG (15 μg/m³) least once.
• Nine sites were above the PM₁₀ annual 2021 WHO AQG at least once each year over this four-year period. These sites were Arrowtown, Ashburton, Blackwood St (Tahunanui), Blenheim Bowling Club, Geraldine, Gore at Main Street, Pomona Street (Invercargill), Timaru Anzac Square, and Woolston (Christchurch).

For the sites analysed for trends during the 10-year period between 2011 and 2020:

• On an annual basis, 69 percent were improving (24 of 35) and 6 percent were worsening (2 of 35) (figure 2). No trend could be determined at 26 percent of sites (9 of 35).
• Twenty-four of 48 sites (50 percent) had an improving trend in winter. The fastest rates of improvements were at Milton, Timaru Anzac Square, and Woolston (Christchurch).
• In summer, 6 of 43 sites (14 percent) had a worsening trend and 6 of 43 sites (14 percent) had an improving trend.

Figure 1: Days above 24-hour 2021 World Health Organization air quality guideline for PM₁₀, 2017–20

Figure 2: PM₁₀ trends, 2011–20

Measurement and assessment

Regional councils and unitary authorities monitor PM_2.5 concentrations in their regions. Data from 19 sites for state and 12 for trends, located across nine regions, were used in this report.

New Zealand is one of the few developed countries without a 24-hour average standard for PM_2.5. Consequently, short-term exposure to PM_2.5 has been assessed against the 2005 WHO 24-hour average guideline of 25 μg/m³. Long-term exposure is assessed against the 2005 WHO annual average guideline of 10 μg/m³.

We also assess against the more stringent air quality guidelines that the World Health Organization recommended in September 2021 for PM_2.5: 24-hour average of 15 μg/m³ and an annual average of 5 μg/m³.

Key findings

In the four-year period between 2017 and 2020:

World Health Organization (WHO)

2005 air quality guidelines

• Sixteen of 19 sites (84 percent) were above the PM_2.5 24-hour 2005 WHO AQG (25 μg/m³); most of these sites are classified as residential.
• Blenheim Bowling Club, Masterton East, and Anzac Square (Timaru) were above the PM_2.5 24-hour 2005 WHO AQG most often: 28–73, 28–43, and 23–46 days per year, respectively.
• The majority (82 percent) of days above the PM_2.5 24-hour 2005 WHO AQG over this period occurred in winter (June, July, August), and 17 percent occurred in autumn (March, April, May).
• Seven of 19 sites (37 percent) were above the PM_2.5 annual 2005 WHO AQG (10 μg/m³) at least once. These were Blenheim Bowling Club, Geraldine, Kaiapoi, Masterton East, Masterton West, Rotorua at Edmund Rd, and Anzac Square (Timaru).
• Blenheim Bowling Club was above the PM_2.5 annual 2005 WHO AQG each year over this four-year period.

2021 air quality guidelines

• Eighteen of 19 sites (95 percent) were above the PM_2.5 24-hour 2021 WHO AQG (15 μg/m³); most of these sites are classified as residential.
• Blenheim Bowling Club, Masterton East, and Anzac Square (Timaru) were above the PM_2.5 24-hour 2021 WHO AQG most often: 98–122, 77–88, and 63–86 days per year, respectively (figure 3).
• The majority (73 percent) of days above the PM_2.5 24-hour 2021 WHO AQG over this period occurred in winter (June, July, August), and 23 percent occurred in autumn (March, April, May).
• Eighteen of 19 sites (95 percent) were above the PM_2.5 annual 2021 WHO AQG (5 μg/m³) at least once.
• Nine sites (Ashburton, Blenheim Bowling Club, Geraldine, Masterton East, Masterton West, Anzac Square (Timaru), Waimate Kennedy, Wainuiomata, and Woolston (Christchurch)) were above the PM_2.5 annual 2021 WHO AQG each year over this four-year period.

For the sites analysed for trends in the 10-year period between 2011 and 2020:

• On an annual basis, PM_2.5 concentrations improved at four out of eight sites (50 percent), worsened at one site (13 percent) (figure 4), and trends were indeterminate at three sites (38 percent).
• Concentrations in winter improved at three out of eight sites. Two sites in Auckland (Patumahoe and Penrose) had worsening concentrations in summer, with Patumahoe also having worsening concentrations in autumn. The Woolston (Christchurch) site had improving PM_2.5 concentrations across all seasons.

Figure 3: Days above 24-hour 2021 World Health Organization air quality guideline for PM_2.5, 2017–20

Figure 4: PM_2.5 trends, 2011–20

Nitrogen dioxide (NO₂) is a gas primarily generated by burning fossil fuels, mainly by motor vehicles (particularly diesel vehicles) but also from industrial emissions and home heating. Because nitrogen dioxide concentrations are closely associated with vehicle emissions, they can be used as a proxy for other motor vehicle-related pollutants such as benzene, black carbon (a form of PM_2.5, also known as soot), and volatile organic compounds.

There are health impacts from short-term and long-term exposure to nitrogen dioxide. Short-term exposure to high concentrations of nitrogen dioxide causes inflammation of the airways and respiratory problems and can cause asthma attacks (US EPA, 2016). Short-term exposure may also trigger heart attacks and increase the risk of premature death (US EPA, 2016). Long-term exposure may cause asthma to develop and lead to decreased lung development in children. It may also increase the risk of certain forms of cancer and premature death (US EPA, 2016). Nitrogen dioxide also contributes to brown haze, which occurs in Auckland, and which is associated with an increase in hospital admissions.

Nitrogen dioxide also contributes to the formation of ground-level ozone and secondary particulate matter (when gases in the atmosphere react in the presence of sunlight), both of which can have negative health impacts.

Nitrogen dioxide can also have ecological impacts. It can cause injury to plant leaves and reduce growth in plants that are directly exposed to high levels (US EPA, 2008). In the atmosphere, nitrogen dioxide can combine with water to form nitrate, which has been shown to cause acidification and have negative effects on freshwater ecosystems. It can also affect ecosystems by acting as a nutrient (Payne et al, 2017).

New Zealand’s COVID-19 response in 2020 led to a notable short-term improvement in air quality, particularly as a result of decreased nitrogen dioxide concentrations due to reduced traffic emissions (Talbot et al, 2021a, b). During the most restrictive alert level period (level 4), nitrogen dioxide concentrations reduced by 34 to 66 percent. The speed of the ‘bounce-back’ in concentrations varied according to location, but largely increased in line with increases in on-road vehicle volume as restrictions eased.

Measurement and assessment

The National Environmental Standards for Air Quality (NESAQ) for nitrogen dioxide requires regional councils and unitary authorities to undertake monitoring where nitrogen dioxide concentrations may be likely to breach the standard. Data from seven sites for state and nine for trends, located across three regions, were used in this report.

Because motor-vehicle emissions are the major source of nitrogen dioxide, the Waka Kotahi NZ Transport Agency also operates a network of passive nitrogen dioxide samplers at sites near roads, and urban background areas. These types of samplers do not meet regulatory standards but do allow for more widespread and cost-effective data collection. As such, this monitoring can provide information on concentrations but cannot be used to assess compliance with the nitrogen dioxide standard. Data from 186 sites for state and 110 for trends, located across 16 regions, were used in this report.

In New Zealand, short-term exposure to nitrogen dioxide is assessed against the NESAQ 1-hour average standard of 200 μg/m³ (nine exceedances are allowed per year), and long-term exposure is assessed against the 2005 WHO annual average guideline of 40 μg/m³.

We also assess against the more stringent air quality guidelines that the WHO recommended in September 2021 for NO2: a 24-hour average of 25 μg/m³ and an annual average of 10 μg/m³.

Key findings

In the four-year period between 2017 and 2020:

• Queen Street (Auckland) recorded the highest nitrogen dioxide concentration (41.5 μg/m³) averaged over 2017–20. Riccarton Road (Christchurch) recorded the second highest concentration (29.9 μg/m³).
• Nitrogen dioxide concentrations at monitored sites were highest in winter (June, July, August).

National Environmental Standards for Air Quality (NESAQ)

• No site exceeded the NESAQ short-term standard (1-hour average) of 200 μg/m³.

World Health Organization (WHO)

2005 air quality guidelines

• Queen Street (Auckland) was above the NO₂ annual 2005 WHO AQG (40 μg/m³) in 2017 (43.9 μg/m³) and 2018 (43.9 μg/m³).

2021 air quality guidelines

• Five of seven sites (71 percent) were above the 24-hour 2021 WHO AQG for nitrogen dioxide (25 μg/m³); most sites were classified as residential.
• Queen Street (Auckland), Riccarton Road (Christchurch), and Penrose were above the 24-hour 2021 WHO AQG for nitrogen dioxide most often: on 294–309, 179–271, and 51–96 days per year, respectively (figure 5).
• Five of seven sites (71 percent) were above the annual 2021 WHO AQG for nitrogen dioxide of 10 μg/m³ at least once a year.

For the council sites analysed for trends in the 10-year period between 2011 and 2020:

• On an annual basis, nitrogen dioxide concentrations improved at six out of seven sites (86 percent) (figure 6).
• Concentrations in winter improved at five out of nine sites, with the rest indeterminate.

For the Waka Kotahi NZ Transport Agency sites analysed for trends in the 10-year period between 2011 and 2020:

• Seventy-two of 110 sites (65 percent) had improving annual trends while four out of 110 (4 percent) had worsening trends

Figure 5: Days above 24-hour 2021 World Health Organization air quality guideline for nitrogen dioxide, 2017–20

Figure 6: Nitrogen dioxide trends, 2011–20

Sulphur dioxide (SO₂) is a colourless gas with a sharp, irritating odour. It is associated with combustion of fossil fuels (such as coal, diesel, and heavy fuel oil used in maritime vessels) and industrial processes (such as the production of fertilisers and the smelting of mineral ores containing sulphur). Geothermal and volcanic gases are natural sources of sulphur dioxide in New Zealand.

At high levels, sulphur dioxide can have human health and ecological impacts. When inhaled, sulphur dioxide is associated with respiratory problems such as bronchitis. It can aggravate the symptoms of asthma and chronic lung disease and cause irritation to eyes.

It can also interact with other compounds in the air to form sulphate particulate matter, a secondary pollutant. Sulphate particulate matter is associated with significant health effects because of its small size and acidity. It is also a cause of haze, which impairs visibility.

In ecosystems, it can damage vegetation, acidify water and soil (US EPA, 2017), and affect biodiversity.

Measurement and assessment

Regional councils and unitary authorities monitor sulphur dioxide concentrations in their regions. Data from seven sites for state and six for trends, located across three regions, were used in this report.

In New Zealand, short-term exposure to sulphur dioxide is assessed against the NESAQ 1-hour average standard of 350 μg/m³ (lower) (nine exceedances are allowed per year) and 570 μg/m³ (upper), and the 2005 WHO 24-hour average guideline of 20 μg/m³.

We also assess against the less stringent air quality guideline that the WHO recommended in September 2021 for sulphur dioxide: a 24-hour average of 40 μg/m³.

Key findings

In the four-year period between 2017 and 2020:

National Environmental Standards for Air Quality (NESAQ)

• No sites exceeded the short-term sulphur dioxide one-hour NESAQ lower threshold (350 μg/m³) or the upper threshold (570 μg/m³).

World Health Organization (WHO)

2005 air quality guidelines

• Four sites out of seven (57 percent) were above the 24-hour 2005 WHO AQG for sulphur dioxide (20 μg/m³).
• Totara St, Whareroa Marae, and Tauranga Bridge Marina sites (all in Mount Maunganui) were above the 24-hour 2005 WHO AQG for sulphur dioxide most often: on 43–105, 13–51, and 6–27 days per year, respectively.
• Of all days above the 24-hour 2005 WHO AQG for sulphur dioxide recorded during this period, 32 percent were in summer (December, January, February) and 30 percent were in spring (September, October, November).

2021 air quality guidelines

• Whareroa Marae, Totara St, and Tauranga Bridge Marina sites (all in Mount Maunganui) were above the 24-hour 2021 WHO AQG for sulphur dioxide (40 μg/m³).
• These sites were above the 24-hour 2021 WHO AQG for sulphur dioxide, on 1–6, 3–7, and 1–3 days per year, respectively (figure 7).

For the six sites analysed for trends in the 10-year period between 2011 and 2020:

• On an annual basis, trends at four out of five sites (80 percent) were improving (figure 8).
• All seasonal trends were either improving or indeterminate.

Figure 7: Days above 24-hour 2021 World Health Organization air quality guidelines for sulphur dioxide, 2017–20

Figure 8: Sulphur dioxide trends, 2011–20

Ozone (O₃) is a gas found naturally in the atmosphere. However, ozone at ground level is a pollutant primarily generated by human activity that can have harmful effects. Ground-level ozone forms when nitrogen oxides and volatile organic compounds (generated by sources such as motor vehicles and industrial processes) combine in the presence of sunlight.

Exposure to high concentrations of ground-level ozone can cause respiratory health issues and is linked to cardiovascular health problems and increased mortality. Those most at risk include children, older adults, people with asthma, and people who spend a lot of time outdoors, such as outdoor workers. Exposure to ground-level ozone may also be associated with effects on the nervous and reproductive systems, and other developmental effects (WHO, 2013).

High levels of ground-level ozone can also have harmful ecological effects: it can damage vegetation, reduce plant growth (affecting crop and forest yields), and harm sensitive ecosystems (US EPA, 2013).

Measurement and assessment

Two regional councils monitor ground-level ozone concentrations. Data from two sites (in Auckland and Wellington) for state and one site (in Auckland) for trends, were used in this report.

In New Zealand, short-term exposure to ground-level ozone is assessed against the NESAQ 1-hour average standard of 150 μg/m³ and the 2005 WHO eight-hour average guideline of 100 μg/m³.

We also assess against the air quality guidelines that the WHO recommended in September 2021 for ground-level ozone: an eight-hour average of 100 μg/m³ (no change) and a peak season* eight-hour average of 60 μg/m³.

*Average daily maximum 8-hour mean O₃ concentration in the six consecutive months with the highest six-month running-average O₃ concentration.

Key findings

In the four-year period between 2017 and 2020:

• Patumahoe (Auckland) had a higher annual average ground-level ozone concentration (40.1 μg/m³) than Wellington Central (17.3 μg/m³).

National Environmental Standards for Air Quality (NESAQ)

• Neither of the two monitored sites, Patumahoe (Auckland) and Wellington Central, exceeded the NESAQ one-hour average threshold (150 μg/m³).

World Health Organization (WHO)

2005 air quality guidelines

• Neither of the two sites were above the eight-hour 2005 WHO AQG for ground-level ozone (100 μg/m³).

2021 air quality guidelines

• No sites were above the eight-hour or peak season 2021 WHO AQGs for ground-level ozone.
• The peak season daily maximum eight-hour mean in Patumahoe was 59.3 μg/m³ in 2019, just under the 60 μg/m³ guideline.

For the one site analysed for trends in the 10-year period between 2011 and 2020:

• On an annual basis, Patumahoe showed an indeterminate trend.

Carbon monoxide (CO) is caused by the incomplete combustion of fuels, especially in petrol-fueled motor vehicles. However, exposure to carbon monoxide has been dramatically reduced since the introduction of emission standards in the year 2000, which required catalytic converters (an exhaust emission control device that converts toxic gases and pollutants into less-toxic pollutants) to be installed in most vehicles (Bluett et al, 2016).

Carbon monoxide can have a range of health effects even after short-term exposure to relatively low concentrations. When inhaled, carbon monoxide enters the blood stream and attaches to haemoglobin in red blood cells, which transport oxygen around the body. This reduces the amount of oxygen that body tissues receive and can have adverse effects on the brain, heart, and general health. Exposure to low levels can causes dizziness, weakness, nausea, confusion, and disorientation. However, higher levels can cause collapse, loss of consciousness, coma, and death (US EPA, 2010).

Measurement and assessment

Two regional councils monitor carbon monoxide concentrations. Data from six sites for state and 12 for trends, located across two regions (Wellington and Canterbury), were used in this report.

In New Zealand, short-term exposure to carbon monoxide is assessed against the NESAQ running 8-hour average standard of 10 mg/m³ (one exceedance permitted per year) and the 2010 WHO 1-hour average guideline of 35 mg/m³ (WHO, 2010).

We also assess against the air quality guidelines that the WHO recommended in September 2021 for CO: a 24-hour average of 4 mg/m³.

Key findings

In the four-year period between 2017 and 2020:

• Riccarton Road (Christchurch) had the highest average concentrations of carbon monoxide (0.4 mg/m³). The rest of the sites had average concentrations of 0.2 mg/m³ (figure 9).
• Across sites, peak concentrations of carbon monoxide occurred during morning and evening hours.
• Carbon monoxide concentrations were highest in winter (June, July, August), averaging 0.4 mg/m³.

National Environmental Standards for Air Quality (NESAQ)

• No site exceeded the NESAQ running 8-hour average threshold (10 mg/m³).

World Health Organization (WHO)

2010 air quality guidelines

• No site was above the 2010 one-hour WHO AQG for carbon monoxide (35 mg/m³).

2021 air quality guidelines

• No site was above the 24-hour 2021 WHO AQG for carbon monoxide (4 mg/m³).

For the sites analysed for trends in the 10-year period between 2011 and 2020:

• Of the 10 sites assessed for annual trends, nine were improving and one was indeterminate (figure 10).
• During summer, two sites (Ashburton and Masterton West) were worsening, and two sites were improving (Geraldine and Riccarton Road (Christchurch)). The remaining seven sites were indeterminate.

Figure 9: Carbon monoxide average daily concentration, 2017–20

Figure 10: Carbon monoxide trends, 2011–20

Understanding the key sources of air pollutants is critical to managing and improving air quality. Emissions inventories estimate the quantities of pollutants emitted to the air by various sources over a certain time period.

Emissions inventories can provide information on the relative contributions of different sources and how they change over time, but they have a level of uncertainty in their estimates. For this report, an air pollutant emissions inventory was developed to examine sources of particulate matter and gaseous pollutants.

The primary method in the inventory is to use readily available information at a national scale (such as fuel use or production volume) and translate it into the amount of pollution emitted. This method provides national-level emission estimates that are easily updatable, consistent over time, and more complete in terms of sources. An alternative method is direct measurement of emissions at the source, aggregated up to a national total.

Measurement and assessment

A national emissions inventory was developed for the following air pollutants in New Zealand – PM₁₀, PM_2.5, nitrogen oxides (NO_X), carbon monoxide (CO), and sulphur dioxide (SO₂).

This indicator presents data from 2012 up to and including 2019. The year covered by the Greenhouse Gas Inventory (which is a major input to the air pollutant emissions inventory) is 15 months behind the current calendar year to give countries time to collect and process the inventory data and prepare their submission (international reporting guidelines govern what the greenhouse inventory covers and when it is submitted).

Key findings

Nationally in 2019:

• The residential sector (primarily burning wood for home heating) contributed 30 percent of PM_2.5 emissions and 41 percent of carbon monoxide emissions. Almost all particulate matter emissions generated by the residential sector were PM_2.5.
• Dust from unsealed roads was the dominant source of PM₁₀ (28 percent).
• On-road vehicles were the dominant source of nitrogen oxides (39 percent), primarily diesel vehicles.
• Burning coal was a large source of sulphur dioxide emissions (41 percent), primarily from manufacturing and construction and electricity generation. Domestic shipping and aluminium production were also significant sources of sulphur dioxide, at 16 percent and 13 percent respectively.

In the eight-year period between 2012 and 2019:

• Total emissions were lower in 2019 than in 2012 for all pollutants except PM₁₀ (figure 11). Annual emissions of carbon monoxide were down 15 percent compared to 2012 (by more than 87,000 tonnes).
• Transport emissions were lower in 2019 for all pollutants except sulphur dioxide, with emissions of carbon monoxide down 47 percent (by more than 85,000 tonnes) and nitrogen oxides down 12 percent (by more than 8,000 tonnes).
• Emissions from electricity generation were lower in 2019 across all pollutants. Most notably, sulphur dioxide emissions decreased by 40 percent (by more than 5,000 tonnes) due to lower emissions from coal burning.

Figure 11: Sources of air pollution emissions, 2012–19

Air pollution causes a wide range of health impacts. There are numerous international studies on the effects that air pollutants can have on human health, but few studies have measured the health impacts in Aotearoa New Zealand. One New Zealand-based study found that living in a neighbourhood with a higher density of wood burners was associated with an increased risk (28 percent) of nonaccidental emergency department visits in children younger than three years old (Lai et al, 2017).

Measurement and assessment

Due to the difficulty of separating air pollution effects from other causes, modelling is commonly used to estimate health impacts from air pollution. This indicator uses a modelling methodology informed by the Health and Air Pollution in New Zealand (HAPINZ) (2012) study, which was developed in accordance with international best practice (Kuschel et al, 2012).

Note: We are anticipating that this indicator will be updated soon, pending an update to the model. Updated information will be available on the Stats NZ website. This indicator used PM₁₀ as a proxy for all air pollution in New Zealand but the revision currently underway will report on PM_2.5 and nitrogen dioxide.

Key findings

From modelling based on the current Health and Air Pollution in New Zealand (HAPINZ) model (table 2):

• Premature deaths in adults of 30 years or older linked to exposure to human-generated PM₁₀ were estimated to be eight percent lower in 2016 than in 2006 (27 deaths per 100,000 people, compared to 29 in 2006).
• Total hospital admissions due to human-generated PM₁₀ were estimated to be two percent lower in 2016 than in 2006 (14 admissions per 10,000 people compared to 15 in 2006).
  • For cardiac illness, admissions were estimated to be 11 percent lower (five per 100,000 people compared to six in 2006).
  • For respiratory illness, admissions were estimated to be four percent higher in 2016 than in 2006 (noting that rounding makes the admissions total the same: nine admissions per 100,000 people in both years).
• Restricted activity days, when symptoms were sufficient to prevent usual activities such as work or study, were estimated to be 12 percent lower in 2016 than 2006 (31,800 per 100,000 people compared to 36,300 in 2006).

It should be noted that the improvement in health effects from air pollution demonstrated by the data above appears to be largely due to more people living in areas with lower PM₁₀ concentrations, such as Auckland, rather than a reduction in PM₁₀ levels overall. While concentrations have decreased markedly in some other areas, these make only a minor contribution to health impacts calculations because of the smaller populations that are exposed.

Table 2: Modelled health effects from exposure to human-generated PM₁₀ in 2006 and 2016.

Source: HAPINZ Exposure Model (Kuschel et al, 2012), Emission Impossible Ltd