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Transport-related emissions are a significant source of air pollution in New Zealand.

  • What is air pollution?

    Human activities can emit gases and particles into the air. Some of these emissions can have a negative impact on air quality and can harm our health, our environment and our economy. There are also natural sources of pollutants that influence air quality.

    The main pollutants in our air are classed as either particulate matter (PM10, PM2.5) or gaseous pollutants (eg nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), sulphur dioxide (SO2) and ozone (O3)). These include both harmful emissions to human health and greenhouse gas emissions that contribute to climate change.

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  • What are the sources of air pollution?

    In New Zealand the sources of air pollution vary seasonally and by location, but major contributors typically include:

    • vehicle emissions
    • wood burning (for home heating)
    • industry
    • natural occurring sources such as dust, sea salts, and pollens.

    Vehicle emissions can be a significant contributor to local air pollution, especially near heavily travelled or congested roadways, roadways located in low-lying areas or other areas with limited wind or air circulation. Air pollution can also occur during winter months when temperature inversion conditions can ‘trap’ pollutants so they do not disperse as usual.

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  • Where do transport-related pollutants come from?

    Most transport-related air pollution is exhaust emissions from motor vehicles, resulting from the combustion of petrol and diesel fuels.

    There has been a reduction in pollution from individual vehicles as New Zealand’s vehicle fleet modernises, and fuel efficiency and pollution controls improve. However, an increase in the number of vehicles, distances travelled and the number of diesel-fuelled vehicles has offset some of this reduction.

    Other sources of air pollution from transport include brake and tyre wear, and airborne dust generated by travelling on sealed and unsealed roads. Air pollution may also result from road construction and maintenance.

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  • Which air pollutants are of concern?

    Transport-related air pollution is of concern because many of the pollutants that are released are known to cause adverse health effects. Although there are a wide range of pollutants in the emissions, most of the health effects result from the following key indicator pollutants listed below. These pollutants are assessed against national standards, targets and guidelines.

    Nitrogen dioxide (NO2)

    Nitrogen dioxide (NO2) is a brown acidic gas formed by the combustion of fossil fuels (coal, oil and gas). Motor vehicles are a large source of NO2 in urban areas. Nitrogen dioxide increases susceptibility and severity of asthma; lowers lungs’ resistance to infections such as the flu; reduces lung development and function in children; can affect growth in and cause damage to some plants and at high levels, and contributes to the formation of hazes and smog.

    Particulate matter

    Particulate matter (PM) is a collective term used to describe very small solid or liquid particles in the air, such as PM10, dust, smoke or fog. PM10 is extremely small (as seen in the image). Each particle is a fraction of the size of a human hair (1/25th), with a diameter of less than 10 micrometres (1 micrometre = 1 millionth of a metre).

    Fine particles (PM10) are linked strongly to adverse health effects, especially in asthmatics or those with heart or lung disease, and can lead to premature deaths, hospitalisation, increased medication and days off work or school, while larger particles (dust) cause amenity (nuisance) effects such as affecting visibility by creating
    a haze over large areas and can contribute to soiling and corrosion of buildings.

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  • What are the health effects of air pollutants?

    Air pollution (from all sources) is a risk factor for several health conditions, including respiratory infections, heart disease, chronic obstructive pulmonary disorder (COPD), stroke and lung cancer. Health effects may include difficulty in breathing, wheezing, coughing, asthma and worsening of existing respiratory and cardiac conditions. Young people, older people and people with existing health problems may be more vulnerable to the health effects of air pollutants.

    The health effects of air pollution can result in increased medication use, increased doctor or emergency room visits, more hospital admissions, restricted activity days and premature death. The 2016 Health and Air Pollution in New Zealand study (HAPINZ 3.0) attributes a social cost to these health effects. It estimated that the social cost to New Zealand related to air pollution health effects was approximately $15.6 billion per year. Of that around two thirds are attributed to motor vehicle emissions..

    Health and air pollution in New Zealand 2016 (HAPINZ 3.0): findings and implications(external link)
    Our air 2021 (Ministry for the Environment)(external link)

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  • Who is responsible for managing air quality?

    Under the Resource Management Act 1991, the primary responsibility for managing air quality sits with regional councils (for example Environment Canterbury and Waikato Regional Council) and unitary authorities (for example Auckland Council, Nelson City Council). These entities are also responsible for regulating and issuing consents for discharges of pollutants to air.

    The National Environmental Standards for Air Quality (NES) sets minimum air quality standards at the national level. All regional councils and unitary authorities develop a regional policy statement and a regional plan to manage air quality. Some develop a specific plan related to air quality (an ‘air plan’). The standards in regional plans and policy statements must be at least as stringent as the NES.

    National environmental standards for air quality (Ministry for the Environment) (2004)(external link)

    The Ministry for the Environment is responsible for development of national policies, guidance and tools to support management of air quality by the regional councils and unitary authorities.

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  • Exhaust fumes and dust from the road have soiled my house, will Waka Kotahi pay to clean it?

    There are many sources of pollutants that contribute to soiling of buildings, these do include ‘particulate matter’ pollutants in vehicle exhaust, along with other naturally occurring and  pollutants cause by human activity such as dust and wood smoke.

    Waka Kotahi does not compensate property owners who consider their buildings have been soiled by exhaust fumes or dust from road traffic.

    Road-controlling authorities such as Waka Kotahi and local councils do not control vehicle exhaust or road dust emissions from individual vehicles on the road. Waka Kotahi also cannot restrict the classes of vehicles (such as heavy trucks) that use roads because they might cause soiling of nearby buildings.

    During design and consenting of new roads Waka Kotahi does consider the impacts of vehicle emissions on nearby communities.

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  • How does Waka Kotahi manage odours from construction

    Odour emissions are less commonly associated with land transport infrastructure construction than dust emissions, but they still need to be considered in certain cases.

    A common source of odour from construction activities is the application of bitumen to form a road. However, this is only for a short period of time and is generally accepted as a normal activity associated with maintenance. Other discharges of odour can occur when land contaminated with organic wastes has been disturbed (such as closed landfills).

    Offensive odours can cause nausea, headaches, frustration, annoyance and a range of other effects that can affect the quality of life for the individuals exposed.

    Diesel-fuelled trucks, generators and other machinery can also generate excessive odours if their filters and fuel systems are poorly maintained.

    Odour emissions can be mitigated by covering or removing odorous material, using chemical suppressants, and regularly maintaining trucks and machinery.

    For more about assessing, managing and monitoring construction odour emissions, see the following documents:

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  • What is Waka Kotahi doing to manage air quality?

    We promote a range of good management practices for assessing and addressing adverse air quality effects specifically associated with state highways.

    New or altered state highways

    For new or altered state highways, the planning/design stage is one of the best places to address potential environmental and air quality effects because alternative options can be considered early in a project life cycle. Options for assessment are discussed in detail in Waka Kotahi’s Guide to assessing air quality impacts from state highway projects.

    Guide to assessing air quality impacts from state highway projects [PDF, 1.9 MB]

    Options usually focus on either reducing air pollution exposure of people living or working close to the road, or reducing the emissions from the road. Sometimes it can involve both approaches. Examples include:

    • route selection – choosing a route that moves the road away from sensitive receptors
    • buffer distances – maintaining or increasing the separation distance between the road and sensitive receptors
    • land use change – re-zoning land adjacent to the state highway and avoiding reverse sensitivity issues
    • infrastructure design – implementing options for efficient traffic flow such as grade separation, high occupancy vehicle lanes and bus priority lanes
    • network operation – using information and technology to make the best use of transport networks to improve safety, mitigate traffic congestion, increase traveller mobility and convenience and reduce fuel consumption and emissions.

    Existing state highways

    Once the road is built, air quality effects can be managed by optimising how the state highway (including any tunnels) is used, such as providing information and technology to assist motorists with making smarter travel choices before or during their journeys.

    We extensively monitor air quality effects related to the state highway network to assess whether air quality standards are being exceeded.

    State highway maintenance activities

    To minimise air pollution effects resulting from the maintenance of state highways, we require all contracted suppliers to develop and implement an environmental and social management plan, based on ISO 14001, for each network operating contract.

    Environmental and social management plans

    Vehicle emissions

    We ensure that vehicles entering New Zealand comply with current exhaust emissions standards and requirements. Once in service, vehicles must comply with the requirements of the warrant of fitness (WoF) for light vehicles or the certificate of fitness (CoF) for heavy vehicles. Both the WoF and CoF involve a visible smoke check to identify vehicles that are excessively smoky.

    Warrant of fitness
    Certificate of fitness

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  • What is being done about smoky vehicles?

    The government introduced requirements for smoky exhausts as part of an ongoing campaign to reduce vehicle emissions and improve public health and the environment. Since 27 October 2006, all vehicles need to pass a visible smoke check in order to get their warrant or certificate of fitness.

    Further information on smoky exhausts

    In service (on-road) vehicle emissions in New Zealand are governed by land transport rules:

    • The Vehicle Exhaust Emissions Rule 2007:
      • prohibits removal of, or tampering with, a vehicle's emissions control equipment
      • requires a vehicle to pass a five-second visible smoke check during a warrant of fitness or certificate of fitness inspection.
    • The Road User Rule 2004:
      • prohibits a vehicle from emitting visible smoke for 10 or more seconds whilst being driven on the road.

    Environmental standards for vehicles

    The NZ Police are responsible for enforcement of the rules relating to smoky vehicles driven on the road.

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  • How does Waka Kotahi monitor transport-related impacts?

    ‘You can’t manage what you don’t measure.

    The fundamental objective of our air quality monitoring network is to collect data that can be used to make informed decisions to best manage and improve the environment. We do various types of monitoring including:

    • monitoring trends for existing roads
    • assessment monitoring for new/altered roads
    • construction effects monitoring for new/altered roads
    • research and investigative monitoring.

    Air quality effects resulting from vehicles using the existing state highway network are assessed annually using diffusion tubes to measure nitrogen dioxide (NO2). NO2 is generally accepted as a proxy for other motor vehicle-related air pollutants, such as particulate matter (PM10) and carbon monoxide. Monitoring is carried out at around 130 sites across the state highway and local road network and includes areas representing relevant exposure, such as residences and schools.

    National air quality (NO2) monitoring network

    All new and altered state highway projects are required to consider the current air quality in the project area so we can evaluate the project’s impacts on future air quality. We might already hold suitable data, as might regional councils or research organisations. If not, dedicated monitoring may be carried out pre-project or post-project.

    Guide to assessing air quality impacts from state highway projects [PDF, 1.9 MB] 

    Visual assessments of dust, and in some cases dust monitoring, is carried out during road construction so any potentially adverse effects can be identified, and immediate remedial action can be taken (for example to increase the frequency of water spraying to dampen dust emissions). Odour is less commonly associated road construction activities, but occasionally odour monitoring may also be undertaken.

    We also invest in research and investigative monitoring to help us learn more about emissions and air quality impacts. This typically involves one-off studies to review the effectiveness of existing policy or highlight options for new policy development (such as roadside remote sensing, which is useful for identifying and assessing the key trends that influence the emissions performance of the light vehicle fleet).

    All monitoring results are then compared to national and relevant international air quality guidelines and standards for human health and amenity protection.

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  • What are the current levels and trends in transport-related air pollution?

    The Waka Kotahi nitrogen dioxide diffusion tube monitoring network includes sites located in each region, covering all main urban areas. We began monitoring at 48 sites in 2007 and this has grown to around 130 sites covering all towns and cities with populations larger than 45,000 (representing approximately two-thirds of New Zealand's population). Sites are classified as peak sites (kerbside/high concentration), roadside sites and urban background sites. 

    Nitrogen dioxide (NO2) concentrations can decrease rapidly with distance from the road. For example, concentrations at some peak sites represent a highly localised impact that may extend no more than 10 metres. The average of urban background site data is typically around half the concentration of the peak sites. This also reflects the highly localised nature of nitrogen dioxide exposure.

    Between 2010 and 2016, 23 monitors in Auckland, Bay of Plenty, Hamilton, Northland and Wellington (out of 92 monitors across the country with enough data to calculate a trend) had decreasing nitrogen dioxide. Three sites (one in Christchurch and two in Wellington) had an increasing trend. The rest had no definite trend.

    The diffusion tubes are useful as a screening method and to assess pollutant trends. However, results should be considered as indicative only. Diffusion tubes are less accurate than the costlier regulatory continuous monitors (to assess compliance with standards) and generally overread. All but a few peak sites show concentrations below the World Health Organization’s 2005 nitrogen dioxide annual air quality guideline value.

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