State and Impacts

The ambient air quality pollutants of most concern are nitrogen dioxide, particulate matter and ozone.  They can impact on human health and are at levels approaching the relevant limit value or long-term objective. 

Nitrogen Dioxide (NO₂)

Nitrogen dioxide has a direct effect on health. Short-term exposure is associated with reduced lung function and airway responsiveness and increased reactivity to natural allergens. Long-term exposure is associated with increased risk of respiratory infection in children.

Nitrogen dioxide was measured at 14 stations in 2009. Concentrations of nitrogen dioxide were below the limit at all sites except one Dublin city centre site. Annual concentrations measured at suburban and rural sites are significantly lower than those measured at urban stations.

The trend in concentrations shows no discernible change in the last five years. While nitrogen dioxide concentrations are low in rural areas, higher levels in urban areas continue to pose a threat to compliance with the limit value.

Particulate Matter (PM₁₀)

PM₁₀ are very small particles which can penetrate deep into the respiratory tract. Inhalation of these particles can increase the risk, frequency and severity of respiratory and cardiopulmonary disorders.

PM₁₀ was measured at 17 stations in 2009; all stations were compliant with the limit values. Levels were highest at traffic influenced sites in cities and in large towns due to burning of coal and other solid fuel in addition to emissions from traffic.

Levels of PM₁₀ have remained stable during the last five years with a decreasing trend emerging at stations in Zone A (Dublin), Zone B (Cork) and Zone C (21 cities and towns with population >15,000).  This may be attributed to decreases in emissions from traffic in the cities and large towns due to cleaner vehicles. The decrease is not seen in Zone D because levels in smaller towns and rural areas are influenced by a wider range of PM10 sources including emissions from residential fuel use, industry and agriculture.

Ozone (O₃)

At ground level, higher concentrations of ozone in the air have adverse implications for human health and for crops and other vegetation. With respect to human health, high concentrations of ozone affect the functioning of the respiratory system.

Ozone was measured at 11 stations in 2009.  Concentrations measured at all stations were below the target value. However, levels at three stations exceeded the long-term objective.  Levels in Ireland are highly influenced by transboundary sources and are higher at the west coast than in the east of the country. In urban areas ozone is depleted through reactions with traffic-emitted pollutants, therefore levels of ozone are higher in rural areas than in urban areas.

Ozone concentrations are strongly influenced by meteorological conditions; higher levels of ozone occur in warm sunny conditions. Unlike most of mainland Europe, Ireland does not experience notable ozone pollution.