Ozone concentrations

Do ozone concentrations in Malta meet EU air quality standards?

Ozone (O3) is formed when nitrogen oxides and volatile organic compounds react in sunlight. It is a harmful pollutant at ground level since it impairs respiratory systems and reduces crop yields. The main O3 precursors emerge from primary traffic and power generation emissions; however the majority of O3 affecting Malta is of transboundary origin.

In 2009, the EU limit value (not to be exceeded more than 25 times per year or 6.8 per cent of days measured) was exceeded on 25 or eight per cent of days measured in Għarb, while exceedances were recorded on two or 0.6 per cent of days measured in Kordin and on nine or 2.6 per cent of days measured in Żejtun. No exceedances were recorded in Msida. The EU 180µg/m³ hourly information threshold should never be exceeded but concentrations were higher for two hours at the Għarb monitoring station.

Although EU limit values have not been set for annual average O3 concentrations, national annual average O3 concentrations slightly increased by 1.3 per cent between 2008 and 2009. As in previous years, the highest O3 concentrations were recorded in rural localities less affected by traffic, with Għarb in Gozo, again registering the highest annual average concentration (135.3µg/m3). With respect to individual sites, readings from the Għarb monitoring station registered the highest annual average O3 concentration (154.3µg/m3) in 2009. The number of sites with an annual average concentration exceeding 100µg/m3 increased from 69 out of 133 in 2008 to 75 out of 131 sites in 2009.