An area, formally notified in the New Zealand Gazette, that is likely or known to have unacceptable levels of pollutants, or may require air-quality management.

Annual average
The average of all values in a range of samples or measurements over a given year.

A heavy metal and in New Zealand comes mainly from burning timber treated with preservative copper-chromate-arsenic. Arsenic can be emitted into the air by burning offcuts of treated timber from building projects for home heating. Some industrial processes also emit arsenic.

A volatile organic compound. Motor vehicles and home heating are the main sources, and some industrial activities. Benzene can affect the nervous system and is associated with cancer.

Benzo(a)pyrene (BaP)                                    
A polycyclic aromatic hydrocarbon. Largely emitted from the combustion of fuels (such as wood and coal from home heating), vehicle emissions, and some industrial processes. BaP can irritate the eyes, nose, and throat, and is associated with cancer.

Where the concentration of a pollutant exceeds the levels permitted under a national environmental standard (see also exceedance).

Busy local road                                                  
Where the annual average daily traffic count is greater than 20,000 vehicles per day or is a known hot-spot for traffic congestion.

Carbon monoxide                                            
A colourless and odourless gas produced by incomplete burning of carbon-containing fuels such as wood, coal, petrol, and diesel.

The measure of the relative quantity of a given substance contained within a specified medium (eg the amount of pollution in the air). Concentrations are given in mass per unit volume of air.

The ability of a substance to wear away the surface of another substance by a chemical reaction.

The release of a pollutant into the atmosphere; its concentration in the air will depend on how the pollutant subsequently disperses in the atmosphere.

Where the concentration of a pollutant exceeds a standard or a guideline.

Contact with a chemical, physical, or biological agent that can have either a harmful or beneficial effect.

Fossil fuel                                                            
Coal, natural gas, liquefied petroleum gas (LPG), crude oil or a fuel derived from crude oil (including petrol and diesel), so called because they have been formed from ancient organic matter over long periods of time

Fuel combustion                                               
The controlled burning of solid, liquid, or gaseous fossil fuels to generate heat or energy.

Ground-level ozone                                        
A colourless and odourless gas that is produced by other gases reacting in the presence of sunlight. Examples of pollutants that form ozone are oxides of nitrogen and volatile organic compounds caused by transport, home heating, and industrial processes.

Heavy metal                                                       
Subset of elements which exhibit metallic properties and have relatively high atomic weight. They are naturally occurring within the air, but can be emitted from anthropogenic activities, such as vehicle tyre/brake wear and battery and steelmaking facilities.

Microgram per cubic metre (µg/m3)
A measuring unit of density used to measure volume in cubic millimetres to estimate weight or mass in micrograms.

Monitoring site                                                 
The site where equipment to sample and/or measure the quality of air is deployed.

National environmental standards           
Regulations produced by central government under the Resource Management Act 1991 (sections 43 and 44), which are binding on local authorities.

Nitrogen dioxide                                              
A reddish-brown, pungent gas that is produced mainly from the combustion of fossil fuels (coal, gas, diesel, and oil) and some industrial processes.

Particulate matter                                            
Small airborne particles composed of solid and/or liquid matter.

Any substance (including gases, odorous compounds, liquids, solids, and micro-organisms) or energy, or heat, that results in an undesirable change to the physical, chemical, or biological environment.

PM10 particulates                                             
Airborne particles that are 10 µm or less in diameter (about a fifth of the thickness of a human hair). They are produced by the combustion of wood and fossil fuels, as well as by various industrial and natural processes.

PM2.5 particulates                                            
Airborne particles that are 2.5 µm or less in diameter and mostly come from combustion sources (see PM10 particulates). Most particulate matter from natural sources is larger than 2.5 µm in diameter.

Rural areas                                                          
Determined by Statistics NZ by classifying areas that are urban. See New Zealand: An urban/rural profile update [Statistics New Zealand website] for more information.

Screening method                                           
Any non-standard method that provides indicative data for a particular contaminant. It uses lower resolution instruments. It cannot be used to determine compliance with a standard or guideline.

Standard method                                             
An air quality monitoring method recommended by a national or international body that can be used to determine compliance with a standard or guideline.

Sulphur dioxide                                                
A colourless gas with a pungent smell, produced during the combustion of fuels containing sulphur, such as coal and diesel.

Temperature inversion                                  
A layer of warm air that sits over a layer of cooler air near the ground. Because cool air is heavier than warm air, it often remains trapped close to the ground. Air pollution that gets trapped beneath the inversion layer can build up, causing air pollution concentrations to increase.

Valid data                                                            
Valid data only includes observations that reflect actual conditions being monitored. For example, monitors may register spurious values or collect data while they are being calibrated. These observations need to be removed otherwise the datasets would include known measurement errors. A requirement for 75 percent valid data ensures that the data is representative over the course of a year.

Volatile organic compound                          
Any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions.

Weather conditions                                        
Prevailing weather (eg wind, precipitation, temperature) conditions.

Wood burner                                                     
An appliance designed for or capable of burning wood, generally to provide heat for households.


Published by - Mfe and Statistics