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Good Practice Guide on Assessing Discharges to Air from Land Transport

Foreword by the Ministry

Acknowledgements

Key Data Sources & Models

1 Introduction

2 Legislative and Policy Context

3 Assessing Discharges to Air from Transport

4 The Assessment Process

5 Air Quality Criteria

6 Tier 1 Screening Assessment Process

7 Tier 2 Conservative Assessment Process

8 Tier 3 Detailed Assessment Process

9 Assessment of Community Impacts and Comparison of Project Options

10 Mitigation Options

11 Monitoring Project Effects

References

Appendix 1: Calculations and Data

Appendix 2: Traffic and Transport Data

Appendix 3: Vehicle Emissions and Effects

5 Air Quality Criteria

To assess the air quality impacts of transport projects, changes in air quality need to be predicted and assessed against air quality criteria. The following air quality criteria are available for use in assessing discharges to air from land transport in New Zealand:

• New Zealand ambient air quality standards (Schedule 1 of the Standards)
• New Zealand Ambient Air Quality Guidelines (Ministry for the Environment, 2002).

For those pollutants not covered by the ambient air quality standards or the Ambient Air Quality Guidelines identified above, approaches to derive criteria are given in section 8.5. Health risk assessment techniques should be applied when international air quality criteria are not available.

Consenting authorities can specify stricter (but not more lenient) targets in their regional plans, and some do so for some contaminants. It is important to check the requirements of the relevant regional plan before undertaking any assessment of the discharges to air from land transport.

5.1 National Environmental Standards for Air Quality

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

• fine particulate matter that is less than 10 micrometres in diameter (PM₁₀)
• nitrogen dioxide (NO₂)
• carbon monoxide (CO)
• sulphur dioxide (SO₂).
• ozone (O₃).

The ambient air quality standards comprise acceptable concentrations for a particular time average, with a specified number of permissible exceedances each year, as summarised in Table 5-1. An explanation of how to apply the ambient air quality standards is provided in the Updated Users Guide (Ministry for the Environment, 2005). A number of key issues that are relevant to the assessment of discharges from land transport are discussed here.

The 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 buildings
• inside tunnels
• inside vehicles.

Table 5-1: Ambient air quality standards 2005

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 standards for assessment purposes

The regulations place constraints on resource consents depending on the pollutant, the existing air quality of an airshed relative to the ambient air quality standards, and the date of the application. The following sections describe requirements for resource consents to discharge contaminants to air. Although these requirements may not directly apply to transport projects, which do not require a discharge consent, they are relevant in 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 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 on the Standards, and their applicability, can be found in the Updated Users Guide (Ministry for the Environment, 2005).

5.2 Ambient air quality guidelines

The 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.

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: Ministry for the Environment Ambient Air Quality Guidelines, 2002

Table 5-4>: Critical levels for protecting ecosystems

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 Non-criteria air pollutants

Australia's National Environmental Protection Council recently released the National Environmental Protection Measure (Air Toxics) (Australian NEPC, 2004). This puts in place a monitoring framework for five pollutants. It includes toluene and xylene, which are not covered by the New Zealand standards and guidelines. Schedule 3 of the measure provides monitoring assessment levels which, if exceeded, provide a prompt for further investigation. The NEPC criteria should be applied for assessments of toluene and xylene.

For other pollutants not included in either the Standards or the Ambient Air Quality Guidelines (Ministry for the Environment, 2002), there are a number of extensive sets of assessment criteria that may be referred to including:

• Texas: effects screening levels (Texas Commission on Environmental Quality, 2003)
• Washington: ambient source impact levels (Washington Department of Ecology, 1998)
• Ontario: point of impingement standards (Ontario Ministry for the Environment, 2001).

It is important to note these criteria have been developed for different modelling averaging times, with the Ontario point of impingement values using 30-minute averages, the Washington ambient source impact levels one-hour averages, and the Texas effects screening levels either one-hour or annual averages. The aim of the guideline should also be considered (eg, whether it is the prevention of health impacts, ecosystem effects, odour nuisance, etc). In general, the criteria taken from these sources should be selected based on the exposure characteristics for the development of interest and the potential effect in the receiving environment.

The criteria should be applied primarily as screening criteria. If the modelling/monitoring results are well within the assessment criteria, then the effects on public health and the environment should be minor. However, if the results exceed the criteria, then a full health risk assessment is required (see section 8.5), and/or action is needed to mitigate the emissions before a designation is recommended.

In the air impact assessment, the range of criteria considered should be identified and a rationale for the criteria selected for an assessment provided.

In the preparation of this good practice guide, other Australian guidelines have been considered, but they are not recommended for use. [Victoria, in its State Environment Protection Policy (Air Quality Management), revised 2001, has an extended list of pollutant design criteria within Schedule A. Within Schedule A, there are three classes:

• class I covers pollutants covered by New Zealand standards and guidelines
• class II covers many non-criteria pollutants
• class III covers carcinogens, mutagens, teratogens and highly toxic compounds.

The class II design criteria were derived from threshold limit values from the US ACGIH (pre-dating 1988), with the design criterion equalling the Threshold Limit Value (TLV) divided by 30. These values have not always been updated as the source occupational health values are revised. Class III provides three-minute time average criteria for carcinogens by taking pre-1988 TLVs divided by 300. Carcinogenic effects are usually considered over annual or lifetime exposure. The use of these short-term criteria is considered to lag behind the developing knowledge and approaches for establishing criteria for air quality protection.]

Workplace Exposure Standards

For some contaminants, in the absence of any other guidance, the Department of Labour Occupational Health and Safety, Workplace Exposure Standards, Time Weighted Average (OSH WES TWA) can be used as assessment criteria. These cover many of the chemicals that might be discharged, but they are set for protecting healthy people in a workplace setting. In order to be used to protect more sensitive members of the community (the very young, the elderly, those health compromised), these standards should be divided by 40 and then assessed over an eight-hour exposure period. For instance, the WES for arsenic is 0.05 mg/m3. Divided by 40 gives an assessment level of 1.25 µg/m³. A discharge should not result in a peak concentration above 1.25 µg/m³ averaged over eight hours.

The use of the factor of 40 here is informal. In the past, a factor of 30 was used. For some applications there is support for applying a factor of 100, or allowing for a safety margin of 10, which equates to applying a factor of 400. Some regional councils have specific guidance, and this should be followed where available. When the method needs to be employed, judgement must be used as to the appropriate factor. It should not be less than 40, but may need to be greater for highly sensitive receiving environments.

Note that in some cases, a specific ambient air quality criterion has been established, and this should be used in preference to the OSH WES. (In the example used for arsenic, the ambient air quality guideline from Table 5-4 is for an annual average at 0.0055 µg/m³. This is formulated as an annual average to account for longer-term effects. In general, both the short-term WES figures and the long-term ones should be met.)