Air monitoring

Carbon monoxide is a poisonous gas.  Prolonged exposures at moderate concentrations can cause headaches and dizziness.  Chronic exposure at lower levels has been linked to an increased incidence of heart disease.

The air quality guidelines for carbon monoxide were exceeded on a number of occasions in the past in Tauranga (Nichol et. al.,1996), which indicates that air quality is already being compromised.  This was recognised in the Operative Regional Air Plan released by Council, and a number of actions were proposed for dealing with this issue.  Carbon monoxide monitoring is therefore an important component of the Air NERMN programme, to determine the current extent of any problem, and any improvements that occur as the result of any regional (or national) initiatives.

There is increasing concern throughout the world about the possible health effects of coarse particulate matter.  These are defined as particulate matter less than 10 µm in diameter, although in some countries more emphasis is now being placed on the smaller fraction (termed fine particulate matter), less than 2.5 µm (PM_2.5) in diameter.

Particulate size comparisons

In New Zealand the main source of PM₁₀ emissions in most areas during the winter months is solid fuel burning for domestic heating, although industrial contributions may also be significant in a number of locations.  Domestic home heating is also responsible for the majority of the PM_2.5 emissions in most locations as most of the PM₁₀ emissions from this source are the smaller PM_2.5 size fraction.  Motor vehicle emissions may also be a major source of PM₁₀ and PM_2.5 in Auckland, although further work is being carried out to assess this.

The characteristics, sources and potential health effects of larger or "coarse" particles and smaller or "fine" particles are very different.  Coarse particles come from sources such as windblown dust from exposed surfaces like building sites and unsealed roads, from mines and quarries, and some industrial activities.  Fine particles are generally emitted from activities such as industrial and residential combustion, and from vehicle exhaust.  Fine particles are also formed in the atmosphere from gases such as sulphur dioxide, nitrogen oxides and volatile organic compounds that are emitted from combustion processes and become particles because of chemical transformations in the air.

Coarse particles can deposit in the upper regions of the human respiratory system and may contribute to health problems such as bronchitis and aggravation of asthma.

Fine particles can deposit deeply in the lungs, and are therefore more likely to contribute to a range of health effects, which have been found in a number of recently published epidemiological studies.

These effects include:

• Increased hospital admissions and emergency room visits due to respiratory complaints.
• Aggravated asthma.
• Acute respiratory symptoms including severe chest pain and aggravated coughing.
• Chronic bronchitis.
• Decreased lung function which can be experienced as shortness of breath.
• Premature death.

This makes it important for Council to continue to develop a good understanding of the current levels of airborne particulate matter throughout the region, as part of the Air NERMN programme.  Measurements are being mainly directed at urban areas because the major contributors are likely to be motor vehicles and residential heating using solid fuel fires, especially wood burners.

The smell of hydrogen sulphide (H₂S) is an obvious feature of New Zealand geothermal areas, most of which are found in the Bay of Plenty.  This gas is very toxic at high concentrations, but little is known about its health effects at the lower levels found in most parts of Rotorua and other geothermal areas.

Field monitoring data shows that geothermal activity in Rotorua has increased over the last few years, probably as a result of the reduced abstraction rates and more re-injection.  If this trend continues it will be important to determine whether hydrogen sulphide levels in the ambient air are also being affected.

Nitrogen dioxide is not usually released directly into the air. Nitrogen dioxide forms when nitrogen oxide (NO) and other nitrogen oxides (NO_x) react with other chemicals in the air to form nitrogen dioxide.

The main source of nitrogen dioxide resulting from human activities is the combustion of fossil fuels (coal, gas and oil), especially petrol and diesel used in motor vehicles.  Other sources of nitrogen dioxide include the refining of petrol and metals, commercial manufacturing, and food manufacturing. Natural sources of other nitrogen oxides include volcanoes and bacteria.

The main health effect of nitrogen dioxide is on the respiratory system. Inhalation of nitrogen dioxide by children increases their risk of respiratory infection and may lead to poorer lung function in later life. There is also an association between nitrogen dioxide concentrations in the air and increases in daily mortality and hospital admissions for respiratory disease. Nitrogen dioxide can decrease the lungs' defences against bacteria, making them more susceptible to infections, and can also aggravate asthma.

Sulphur dioxide is produced mainly from the combustion of fossil fuels that contain sulphur, such as coal and oil (for example, coal being burnt in a home fireplace for heating and diesel-powered vehicles). Sulphur dioxide is also produced from some industrial processes, such as fertiliser manufacturing.

Natural sources of sulphur dioxide include geothermal activity.

Sulphur dioxide can cause respiratory problems, such as bronchitis, and it can irritate the nose, throat and lungs. It may cause coughing, wheezing, phlegm and asthma attacks. The effects are worse during exercising.