View all publications

5 Air Quality Criteria

The extent to which the impacts on air quality caused by a transport development are considered acceptable is judged by the use of air quality criteria. The New Zealand regulatory framework contains the following air quality criteria:

  • national environmental standards for air quality

  • national ambient air quality guidelines

  • objectives and policies in regional plans.

It is important to note that regional plans are statutory instruments under the RMA. If the air quality objectives in a regional plan are more stringent than the national environmental standards for air quality, then the regional plan takes precedence. For this reason it is very important to check the requirements of the relevant regional plan before undertaking any assessment of the discharges to air from land transport.

New Zealand and other international air quality criteria are discussed in more detail below.

A thorough air quality assessment (some Tier 2 and all Tier 3) should address both short-term and long-term impacts. This means you will need to use air quality criteria with both short- and long-term time averages. Air quality criteria published by different agencies may overlap, complement or sometimes outright contradict each other for some pollutants and some time averages. It is very important, therefore, when selecting air quality criteria for an air quality assessment, that the fundamental purpose of the standard or guideline is understood. Similarly, the application of the criteria should be considered.

It should also be noted that air quality criteria may become outdated. Check the Ministry for the Environment website (www.mfe.govt.nz) for any updates to the national ambient air quality standards or guidelines discussed in this section.

In all cases, the assessment should explain which criteria have been selected and why. For those pollutants not covered by the criteria discussed below, or in cases where the criteria are exceeded, health risk assessment techniques should be applied.

5.1 National environmental standards for air quality

Schedule 1 of the Standards provides ambient concentration limits for the following pollutants:

  • carbon monoxide (CO)

  • nitrogen dioxide (NO2)

  • ozone (O3)

  • fine particulate matter that is less than 10 micrometres in diameter (PM10)

  • sulphur dioxide (SO2).

The primary purpose of the national ambient air quality standards is to provide a guaranteed level of protection for the health of all New Zealanders.

The national ambient air quality standards, therefore, comprise acceptable concentrations for a particular time average, with a specified number of permissible exceedances each year, as summarised in Table 5.1.

Guidance on applying the national ambient air quality standards is provided in the Updated Users’ Guide (Ministry for the Environment, 2005). A number of key issues relevant to the assessment of discharges from transport are discussed here.

The national ambient air quality standards apply in the open air everywhere people may be exposed. This includes roadside verges, residential areas, central business districts, parks and beaches. Areas that are not in the open air and where the Standards do not apply include:

  • inside a house

  • inside tunnels

  • inside vehicles.

Table 5.1: National ambient air quality standards 2004

Pollutant

Standard

Time average

Allowable exceedances per year

PM10 (particulate)

50 µg/m3

24-hour

1

Nitrogen dioxide (NO2)

200 µg/m3

1-hour

9

Carbon monoxide (CO)

10 mg/m3

8-hour

1

Sulphur dioxide (SO2)

350 µg/m3
570 µg/m3

1-hour
1-hour

9
0

Ozone (O3)

150 µg/m3

1-hour

0

When assessing the potential impacts of discharges to air from land transport, careful judgement is required to determine whether people may be exposed. General guidance on determining exposure for assessment purposes is provided in Table 5.2.

Table 5.2: Location and applicability of the Standards for assessment purposes

Averaging period

Locations where assessment against the Standards should apply

Locations where assessment against the Standards should not apply

1 hour

This includes any outdoor areas where the public might reasonably be expected to spend one hour or longer, including pavements in shopping streets, as well as facades of any building where the public might reasonably be expected to spend one hour or longer.

Any industrial premises that have resource consents (for that pollutant).

24 hours and 8 hours

This includes all outdoor locations where members of the public might be regularly exposed (eg, residential gardens) as well as facades of residential properties, schools, hospitals, libraries, etc.

Any industrial premises that have resource consents (for that pollutant).

All

 

In any enclosed space (ie, not in the open air) including:

  • indoors

  • inside tunnels

  • inside vehicles.

The regulations place constraints on resource consents depending on the pollutant, the existing air quality of an airshed relative to the national ambient air quality standards, and the date of the application. Although transport projects generally do not require a discharge consent, the national ambient air quality standards are relevant to assessing whether a project meets the purposes of the RMA (eg, safeguarding the life-supporting capacity of air).

In particular, for new designations and land-use consents after September 2005, territorial authorities and/or requiring authorities should consider the national ambient air quality standards. The authority will need to consider the potential impacts of a new designation or land-use consent on air quality, and the subsequent impact this may have on future resource consent applications.

A full discussion of the Standards, and their applicability, can be found in the Updated Users Guide (Ministry for the Environment, 2005).

5.2 New Zealand air quality guidelines

The national ambient air quality standards are based on the existing Ambient Air Quality Guidelines (Ministry for the Environment, 2002). These guidelines were developed following a comprehensive review of international and national research, and are widely accepted among New Zealand practitioners. The Ambient Air Quality Guidelines were published by the Ministry for the Environment as guidance under the RMA. They provide the minimum requirements that outdoor air quality should meet in order to protect human health and the environment.

The primary purpose of the national Ambient Air Quality Guidelines is to promote sustainable management of the air resource in New Zealand.

Guideline levels for pollutants (and averaging periods) not covered by the Standards still apply. The Standards replace any previous guideline levels for that particular pollutant and averaging period. In addition to the human health-based guidelines presented in Table 5.3, guidelines for ecosystem protection are provided for sulphur dioxide, sulphate particulate, nitrogen dioxide, ammonia, ozone and fluoride in Table 5.4.

Table 5.3 National Ambient Air Quality Guidelines, 2002

Indicator

Level

Averaging time

Carbon monoxide

30 mg/m3

1 hour

Fine particulates (PM10)

20 µg/m3

Annual

Fine particulates (PM2.5)

25 µg/m3

24 hours – monitoring value only

Nitrogen dioxide

100 µg/m3

24 hours

Sulphur dioxide

120 µg/m3

24 hours

Ozone

100 µg/m3

8 hours

Hydrogen sulphide

7 µg/m3

1 hour

Lead

0.2 µg/m3

3-month moving average, calculated monthly

Benzene (2002)
Benzene (2010)

10 µg/m3
3.6 µg/m3

Annual
Annual

1,3 butadiene

2.4µg/m3

Annual

Formaldehyde

100 µg/m3

30 mins

Acetaldehyde

30 µg/m3

Annual

Benzo(a)pyrene

0.0003 µg/m3

Annual

Mercury (inorganic)
Mercury (organic)

0.33 µg/m3
0.13 µg/m3

Annual
Annual

Chromium V1
Chromium metal and Chromium III

0.0011 µg/m3
0.11 µg/m3

Annual
Annual

Arsenic (inorganic)
Arsine

0.0055 µg/m3
0.055 µg/m3

Annual
Annual

Table 5.4: Critical levels for protecting ecosystems

Contaminant and land use

Critical level

Averaging period

Additional requirements

Sulphur dioxide:

 

 

 

  • agricultural crops

30 µg/m3

Annual and winter average

 

  • forest and natural vegetation

20 µg/m3

Annual and winter average

 

  • lichen

10 µg/m3

Annual

 

Sulphate particulate:

 

 

 

  • forests

1.0 µg/m3

Annual

Where ground-level cloud present > 10% of time

Nitrogen dioxide

30 µg/m3

Annual

 

Ammonia

8 µg/m3

Annual

 

Ozone:

 

 

 

  • forests

21,400 µg/m3/h

6 months

 

  • semi-natural vegetation

6,420 µg/m3/h

3 months

 

  • crops (yield)

6,420 µg/m3/h

3 months

 

  • crops (visible injury)

428 µg/m3/h

5 days

Daytime vpd below 1.5 kPa

1,070 µg/m3/h

5 days

Daytime vpd above 1.5 kPa

Fluoride:

 

 

 

  • special land use

1.8 µg/m3

12 hours

 

1.5 µg/m3

24 hours

 

0.8 µg/m3

7 days

 

0.4 µg/m3

30 days

 

0.25 µg/m3

90 days

 

  • general land use

3.7 µg/m3

12 hours

 

2.9 µg/m3

24 hours

 

1.7 µg/m3

7 days

 

0.84 µg/m3

30 days

 

0.5 µg/m3

90 days

 

  • conservation areas

0.1 µg/m3

90 days

 

Notes: Critical levels for NO2 assume that either O3 or SO2 are also present at near guideline levels. Critical levels for O3 are expressed as a cumulative exposure over a concentration threshold referred to as AOT40 values (accumulative exposure over a threshold of 85.6 µg/m3, at 0°C), calculated as the sum of the difference between hourly ambient O3 concentrations and 85.6 µg/m3, when O3 concentrations exceed 85.6µg/m3). O3 is only measured during daylight hours, with a clear global radiation of 50 Wm-2 or greater.

vpd = vapour pressure deficit.

5.3 Regional plans

In 2007 all regional councils had regional air quality plans either operational or in the final stages of becoming operational. The plans reflect particular regional circumstances and may range from being very straightforward, dealing primarily with issues of open burning, to the more complex, with specific rules and plans for meeting the Standards.

It is important to understand the purpose of each regional plan when considering the application of air quality objectives (sometimes referred to as targets or goals).

From a regulatory viewpoint, regional air quality plans are statutory instruments under the RMA and have equal status with the Standards. Where concentration thresholds double up, the more stringent level applies. Thus, a regional air quality objective, that is more stringent than a national ambient air quality standard, supersedes the national standard. The regional air quality objectives cannot, however, be more lenient than the national ambient air quality standards.

5.4 WHO guidelines

Given the increasing evidence of the health impact of air pollution, the World Health Organisation (WHO) revised its existing air quality guidelines for Europe in October 2006 and expanded them to produce the first global air quality guidelines. These guidelines are based on the latest scientific evidence and set targets for air quality to protect the large majority of individuals from the effects of air pollution on health.

The primary aim of the WHO guidelines is to provide a uniform basis for protecting public health from the effects of air pollution. They are intended for worldwide use.

Table 5.5 summarises the updated WHO air quality guideline levels. These include guidelines for PM2.5 and for nitrogen dioxide annual average, which are not currently covered by New Zealand standards or guidelines. The WHO 24-hour average PM2.5 guideline is consistent with the New Zealand monitoring guideline (Ministry for the Environment, 2002). The WHO 24-hour guideline for sulphur dioxide is considerably more stringent than the New Zealand ambient air quality guideline.

Table 5.5: Updated WHO air quality guideline values

Pollutant

AQG value

Averaging time

Particulate matter

PM2.5

PM10

10 µg/m3

25 µg/m3

20 µg/m3

50 µg/m3

1 year

24 hours (99th percentile)

1 year

24 hours (99th percentile)

Ozone (O3)

100 µg/m3

8 hours, daily maximum

Nitrogen dioxide (NO2)

40 µg/m3

200 µg/m3

1 year

1 hour

Sulphur dioxide (SO2)

20 µg/m3

500 µg/m3

24 hours

10 minutes

Notes: Items in bold are not covered by New Zealand standards or guidelines; AQG value = air quality guideline.

5.5 Other air quality criteria

It is unlikely that an assessment of discharges to air from land transport would need to consider any pollutant that is not covered by the New Zealand and WHO standards and guidelines. However, if there are special circumstances that require consideration of another pollutant, there are a number of other air quality criteria that can be used. The Good Practice Guide for Assessing Discharges to Air from Industry (Ministry for the Environment, 2008) includes discussion and recommendations for the use of international air quality criteria and workplace exposure standards.

A number of criteria are available for assessing the effects of air quality. Some take precedence in terms of stringency (eg, regional objectives over the national environmental standards for air quality). Others take precedence in terms of time average and application (eg, the WHO guideline for sulphur dioxide should be applied to new proposals).

In general terms, the following criteria should be selected in the following order of priority:

  • national environmental standards for air quality

  • national ambient air quality guidelines

  • regional objectives (unless more stringent than above criteria)

  • WHO air quality guidelines.