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Introduction

Clean air contributes to New Zealand’s quality of life, not only in terms of people’s health, but also in terms of the beauty of the natural and physical environment.

New Zealand is located in a windy and geographically isolated part of the world. This location means air pollution is often blown away and readily dispersed. New Zealand is not significantly polluted by neighbouring countries and has a low population density and limited amount of heavy industry. The combination of these factors results in good air quality in most locations for most of the time.

As in many developed countries, however, the intensity of human activities in centres of population has an impact on ambient (outdoor) air quality from time to time. An ageing vehicle fleet and the use of coal and wood for home heating can have a detrimental effect on air quality in some areas. In addition, busy, congested roads in some built-up urban areas can adversely affect local air quality.

Natural factors that affect air quality

Two key natural factors that affect air quality are the weather and New Zealand’s geography.

Weather

Pollution levels depend not just on the amount of pollution generated (that is, ‘emissions’), but also on how quickly pollution can be dispersed. In this respect, the weather has a strong influence on pollution levels. For example, ‘temperature inversions’, which trap pollution near ground level, can have an adverse effect on air quality (see box ‘What is a temperature inversion?’ and Figure 7.1). Conversely, particularly windy and unsettled weather can have a beneficial effect on air quality.

Geography

Geographical features also affect the dispersion of air pollution. Settlements in locations with geographical features such as valleys or low-lying land surrounded by hills are often more susceptible to a build-up of pollution.

What is a temperature inversion?

A temperature inversion is a layer of warm air that sits over a layer of cooler air near the ground. Temperature inversion layers typically form just after sundown on still winter nights as the air temperature at ground level rapidly decreases. Because cool air is heavier than warm air, the cool air often remains trapped close to the ground.

Inversion layers occur between 10 and several hundred metres above the ground depending on the weather conditions. Air pollution that gets trapped under the inversion layer can build up, causing air pollution levels to rise (see Figure 7.1).

Figure 7.1: How temperature inversions trap pollution

Human factors that affect air quality

Home heating and transport are the greatest human influences on ambient air quality in New Zealand.

Our air quality is constantly changing. Pollution levels fluctuate as the amount of pollution emitted varies over time. Morning and evening traffic rush hours cause variations over the day. The use of coal and wood for home heating can make air quality in winter very different from that in summer. Even air quality experienced from one year to the next can vary considerably.

Home heating – the main cause of air pollution

Home heating is the main cause of air pollution in populated areas in the winter. On average, 45 per cent of households in New Zealand burn solid fuels (coal and wood) for home heating. At a regional level, this figure varies considerably across the country, ranging from 32 per cent in Auckland to over 75 per cent on the West Coast of the South Island (Ministry for the Environment, 2005).

Pollution from road transport

Pollution from vehicles can be significant in urban areas, particularly on heavily used roads. New Zealand has one of the highest rates of private vehicle ownership in the world: transportation accounts for the largest share of our energy consumption, and is the second fastest-growing sector in terms of energy demand.

Large centres of population, such as Auckland, are more likely to experience air pollution from vehicles than smaller locations (see photo below).

Older and high-mileage petrol vehicles are more likely to be high emitters of pollution than are newer vehicles (Covec, 2005). The average age of New Zealand motor vehicles is 12.4 years. Nearly two-thirds of the newly registered vehicles in New Zealand are used imports rather than new vehicles (see chapter 4, ‘Transport’).

Until 1996, New Zealand’s petrol contained lead additives, which prevented the use of equipment to control exhaust emissions from petrol vehicles. As a result, many vehicles on New Zealand roads are not built to any emission standards.

Busy Auckland motorway.

Source: Courtesy of Gavin Fisher.

Government action on air quality

Central government undertakes a range of regulatory and non-regulatory initiatives to improve New Zealand’s air quality. Below are examples of government initiatives that have been undertaken in recent years.

Warm Homes initiatives

Through the Warm Homes project, central government is working with local government to help New Zealanders reduce the pollution effects of home heating while staying warm. The project aims to ensure all New Zealanders heat their homes cleanly, efficiently, and sufficiently. Pilot programmes were run in Tokoroa, Timaru, and Taumarunui to retrofit homes with insulation and new heating sources, and evaluate the impacts of this on air quality and health. In 2006, the Warm Homes project also ran seven community workshops in six regions across New Zealand.

In addition, the Government has committed $72 million over four years to help New Zealand families live in warm, dry, healthy, and energy efficient homes. This includes $23 million for an interest-free loans scheme to help householders pay for energy efficiency and cleaner heating options. While the main focus is on energy efficiency, $5.4 million will be targeted at the installation of clean forms of heating for low-income households in areas of poor air quality.

Transport initiatives

Petroleum Products Specifications Regulations 2003

These Regulations specify the technical requirements for petrol and diesel supplied for retail sale (excluding aviation, jet boat, and motor racing). Progressive improvements in fuel specifications have reduced the amount of pollutants such as PM10 and benzene that are emitted from vehicle exhausts. Reduction of aromatics and the lowering of vapour pressure also limit the amount of petrol that evaporates into the air during refuelling and from hot vehicle engines.

The Vehicle Exhaust Emissions Rule

This Land Transport Rule, introduced in 2003, requires all motor vehicles entering the New Zealand fleet for the first time to have been manufactured to the applicable emissions standards specified in the rule. Since 2006, the rule has required all vehicles to undergo a visible smoke test check at every compliance test (that is, border entry, warrant of fitness, and certificate of fitness inspections). This complements the Land Transport (Road User) Rule 2004 which requires that vehicles do not emit visible smoke for more than 10 seconds.

At the time of writing, government is consulting on proposed tighter emissions standards for new vehicles and used vehicles entering New Zealand.

Reducing the sulphur content of diesel in New Zealand

In 2002, the Government introduced regulations that reduced the sulphur content of diesel. By September 2002, the sulphur content of diesel available in Auckland and Northland had reduced from 3,000 parts per million to 1,000 parts per million.

In August 2004, levels were further reduced throughout New Zealand to 500 parts per million. This was followed by another decrease to 50 parts per million in January 2006, representing a 60-fold reduction in sulphur content since 2002. The sulphur content in diesel will be further reduced to 10 parts per million in January 2009.

Other programmes and initiatives

Other programmes and initiatives undertaken by central government include educational or public awareness campaigns, or programmes which support initiatives led by local government. Examples include the following initiatives:

  • The Sustainable Management Fund (SMF) was established in 1994 to help communities, iwi, local government, and industry with projects that have a long-term environmental benefit. In 2005, $800,000 of SMF funding was made available to local government to help them implement new air quality monitoring requirements under the national environmental standards for air quality.

  • Recent government research relating to air quality includes work on the health and air quality impacts of home heating, and a performance review of the wood burner design standard.

  • A number of recent transport initiatives contribute to improved air quality in New Zealand. These include the New Zealand Transport Strategy, Towards a sustainable transport system by 2010, the Biofuels Sales Obligation 2006, a draft New Zealand Rail Strategy, and the 'Choke the Smoke' public awareness campaign on vehicle emissions.