Air PollutantsNgā parakino hau takiwā

Air pollutants can be found in air anywhere – outdoors and indoors – at various levels, and are used as indicators of air quality.

Air Quality in Hawke’s Bay

Although air quality in Hawke’s Bay is generally very good, there are times when it is poor, for example:

• On calm, cold winter nights in urban areas, concentrations of fine smoke particles (PM10, PM2.5) can build up, sometimes to unhealthy levels.
• As we live in a strong agricultural and cropping setting, windblown dust or dirt can be a problem when ploughing coincides with strong winds.
• Occasionally localised issues arise, such as odour and agrichemical spray drift, which can create a problem for neighbours when the sources are not well managed. Some of these problems can be avoided by the use of best practice standards which industry groups encourage members to comply with.

Air Pollutants

The Council monitors a number of key ambient (outdoor) air quality parameters, all of which are included in the National Environmental Standards for Air Quality.  The Council also monitors for PM2.5 which is not currently included in the NESAQ but is expected to be included after the current review of the standards.  The standards for these pollutants are based on criteria that relate to health and/or environmental effects and are the minimum requirements that outdoor air quality should meet. Council monitoring shows that the parameters are within safe levels in Hawke’s Bay, with the exception of PM10. For this reason, the Council monitors PM10 continuously at a number of locations in Hawke’s Bay while other pollutants are periodically monitored to check that they remain at safe levels and don’t show any worrying trends.

Key ambient air quality parameters are:

• PM10 – particulate matter that is less than 10 micrometres in diameter
• Carbon monoxide (CO)
• Nitrogen dioxide (NO2)
• Sulphur dioxide (SO2)
• Ozone (O3)

PM10 and PM2.5

PM10 comprises solid or liquid particles less than 10 micrometres in diameter, or roughly a fifth of the width of a human hair. PM2.5 comprises particles less than 2.5 micrometers in diameter and is a subset of PM10. These particles cannot be seen by eye, can remain suspended in air for long periods and is easily inhaled. PM comes from anthropogenic sources such as domestic fires, industrial processes and motor vehicles and but also comprises the likes of pollen, sea salt and wind-blown dust.

The ability to readily inhale PM10 and PM2.5 means that it can contribute to respiratory diseases and it has also been associated with cardiovascular problems. Those at most risk are the elderly, young children and people with existing respiratory and cardiovascular diseases. The smaller the particle, the further it can penetrate into the airways and lungs and the ultra fine particles, less than 0.1 micrometres, may enter the blood stream. There is no known “safe” threshold for PM10 (or PM2.5) so the NES is designed to provide a set level of protection for human health and the environment.

Carbon Monoxide

CO is an odourless, colourless and tasteless gas. It is produced through the incomplete combustion of carbon-based materials such as petrol, wood, coal and gas as well as being emitted from volcanoes and the metabolism of organisms. Health effects are related to its ability to inhibit the oxygen carrying capacity of the blood. This can result in dizziness, nausea and confusion at low levels of exposure while high concentrations can lead to unconsciousness and even death.

Nitrogen Dioxide

NO2 is a reddish-brown acidic gas with a pungent, irritating odour. It can form readily through the reaction of nitric oxide (NO) with other chemicals in the air and the combustion of fossil fuels is a leading contributor to its formation. NO2 plays a role in atmospheric reactions that produce photochemical smog, acid rain and inhalable fine particles. It has an inflammatory effect on the lungs which tends to aggravate asthma and increase susceptibility to infections. It can also be detrimental to plants and corrosive to building materials.

Recently updated World Health Organisation (WHO) guidelines are significantly lower than the NESAQ and our periodic monitoring indicates that we are unlikely to meet these guidelines in parts of urban Napier and Hastings.

Sulphur Dioxide

SO2 is a colourless gas that has a pungent smell. Volcanoes and geothermal activity produce SO2 while anthropogenic sources include the burning of sulphur-containing fuels (such as diesel, coal and oil) and industrial processes such as fertiliser and steel production and aluminium smelting, Similar to NO2, it plays a role in the formation of acid rain and inhalable fine particles. It can affect lung function, causing coughing, wheezing and breathing difficulties and asthmatics are particularly susceptible. It can be toxic to plants and corrosive to building materials in moist conditions. The WHO guideline level is significantly lower than current NESAQ but expect the NZ standards to follow suit.

Ozone

Ozone is a colourless gas which at ground level is a pollutant and component of smog but in the upper atmosphere helps to shield us from harmful ultraviolet radiation. At the earth’s surface it forms from photochemical reactions between nitrogen oxides and volatile organic compounds, some of the main sources of which are motor vehicles, other combustion sources and solvents. Exposure to ozone is linked respiratory problems as it reduces lung function and inflames the linings of the lungs.