Page 5 – Atmospheric pollution
Air pollution in New Zealand
With the exception of some nuisance odours and agricultural spray drift, New Zealanders’ concerns about air quality used to be limited to visible pollution from smoke and fumes in winter. However, there is a growing awareness that air pollution does not have to be visible to cause problems.
By world standards, New Zealand has relatively good air quality. This is due to the coastal location of most of the main centres, the limited amount of heavy industry, the strong winds that disperse pollutants, and the country’s distance from other continents and sources of pollution.
However, some urban areas occasionally have quite high air pollution levels. Pollution typically occurs in Auckland, with its heavy traffic, and Christchurch, which because of its topography is prone to temperature inversion – a layer of warm air traps cooler air, and any pollution, underneath.
Domestic fires and motor vehicles contribute most of New Zealand’s air pollutants. Industry can also cause localised problems. It is important to realise that there is a complex relationship between emissions of pollutants and their presence in the air, because of dispersion processes and chemical reactions. Variations in emissions and the prevailing weather conditions mean that pollution levels are constantly changing during the day, from one day to the next, and from season to season.
Motor vehicles are a source of air pollutants, and yet very little is known about the emissions from New Zealand’s vehicles. A campaign in Auckland in 2003 used roadside sensors to measure emissions of carbon monoxide (CO), hydrocarbons, and nitric oxide (NO) as vehicles drove past. The measurements showed relatively high emission rates. The dirtiest 10% of vehicles were responsible for over 50% of the total carbon monoxide and unburned hydrocarbon emissions, and almost 40% of the total nitric oxide emissions. The cleanest 50% contributed less than 10% of the total emissions.
Keep the home fires burning cleanly
Air pollution is generally perceived as an outdoor issue, but poor indoor air quality can also cause serious health problems. The most common indoor air pollutants are smoke from cigarettes, malfunctioning gas appliances, woodburners and open fires. Emissions of carbon monoxide and nitrogen dioxide from gas appliances and kerosene heaters, and formaldehyde and other organic substances from building materials, can also cause problems. Indoor industrial worksites may generate dust, fumes or odours.
Until the introduction of the Resource Management Act in 1991, air-quality monitoring in New Zealand had largely been in response to specific, perceived problems, and so was quite limited. The act shifted responsibility to the regional councils, and monitoring networks were established and expanded throughout New Zealand during the 1990s. The act also controls emissions from large industrial sources through air-discharge permits, issued by regional councils.
In 1994 the Ministry for the Environment developed a set of guidelines for key air pollutants, including carbon monoxide, particulates, nitrogen dioxide, sulfur dioxide, ozone, hydrogen sulfide and lead. Updated guidelines, incorporating new pollutants (benzene, butadiene, formaldehyde, acetaldehyde, benzopyrene, mercury, chromium and arsenic), were released in 2002.
In July 2004, the government approved 14 national environmental standards aimed at air quality and landfill gas emissions. Replacing the previous air-quality guidelines, they comprised:
- Seven standards for dioxins and toxics. Certain activities that emit hazardous pollutants to air (such as the open burning of tyres) were banned.
- Five ambient air-quality standards, which set maximum allowable levels for key air pollutants.
- One standard for the design of new home wood burners in urban areas.
- One standard for large landfills to collect and destroy landfill gas – to help reduce greenhouse gases.