Pollutants Measured and their Effects

The E.P.A. measures the following atmospheric pollutants

Ozone (O3)

Ozone is a natural component of the atmosphere. Most ozone is found high up in the stratosphere, the layer of the atmosphere between 12km and 50km above sea level. Stratospheric ozone is essential to life on earth as it protects us from harmful rays from the sun.

Ozone is also found in the troposphere, the layer of the atmosphere next to the earth, where it is produced from the reaction of sunlight with volatile organic compounds and nitrogen oxides. Exposure to high concentrations of tropospheric ozone causes chest pains, nausea and coughing in humans. Long term exposure to moderate concentrations of ozone causes a reduction in lung capactity and can worsen heart disease, bronchitis, emphysema and asthma. Trophospheric ozone contributes to the greenhouse effect and subsequent global climate change.

Levels of ozone in Ireland are moderate.

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Sulphur Dioxide (SO2)

The main source of sulphur dioxide in Ireland is burning coal and oil to heat homes and industries and to produce electricity. It is an irritant gas which attacks the throat and lungs. Prolonged exposure to sulphur dioxide can lead to increases in respiratory illnesses like chronic bronchitis. It contributes to the formation of acid rain which damages vegetation and buildings.

Levels of sulphur dioxide in Ireland are low to moderate. Levels have decreased over recent years due to increased use of low sulphur coal (smokeless coal), increased use of natural gas instead of solid fuels and reduced industrial emissions through IPC licensing.

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Nitrogen Dioxide (NO2) and Nitrogen Oxides (NOx)

Nitrogen oxides are produced by high temperature combustion. Emissions from traffic are their main source in Ireland along with electricity generating stations and industry. Nitrogen dioxide is known to affect the throat and lung. The main effects are emphysema and cellular damage. It is also aesthethically unpleasant as it has a brown colour and gives rise to a brown haze. Oxides of nitrogen contribute to the formation of acid rain and the formation of ozone.

Levels of nitrogen oxides in Ireland are moderate but are increasing due to growth in traffic numbers.

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Carbon Monoxide (CO)

The main source of carbon monoxide in Ireland is traffic. It is absorbed into the blood stream more readily than oxygen so the presence of relatively small quantities of it in inhaled air can have harmful effects on human health. Prolonged exposure to carbon monoxide can cause tissue damage and individuals suffering from cardiovascular disease are particularly at risk.

Levels of carbon monoxide in Ireland are low.

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Particulate Matter (PM10 and PM2.5)

There are many sources of particulate matter (dust) including vehicle exhaust emissions (particularly from diesel engines), dust from soil and road surfaces, dust from construction works and industrial emissions. Particulate matter can be formed from reactions between different pollutant gases.

Small particles can penetrate the lungs and cause damage. These are known as PM10 (diameter less than 10µm) and PM2.5(diameter less than 2.5µm).

There are high levels of PM10 in many cities and towns. In smokeless fuel zones, levels of particulate matter decreased after the ban on bituminous coal was introduced.

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Lead (Pb)

The main source of lead in air is from petrol engine exhaust emissions. It is contained in small particles that can be readily inhaled and can enter the lung. They are then absorbed into the bloodstream. High concentrations can retard mental development in children. Long term exposure to low levels of lead can affect the nervous system.

The introduction of unleaded petrol has dramatically reduced emissions. Levels are now very low in Ireland.

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Benzene (C6H6)

Benzene comes from petrol emissions and the evaporation of petrol at petrol stations. It is a carcinogen, ie. it can cause cancer in humans. Acute short-term inhalation of benzene by humans may cause drowsiness, dizziness, headaches, as well as eye, skin, and respiratory tract irritations, and, at high levels, unconsciousness.

Levels of benzene are low in Ireland.

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