Italy tops Euro ozone chart

Concentrations of ground-level ozone, the main component of summer smog, exceeded a critical threshold somewhere in 25 European nations on two out of every three days this spring and summer, with Italy top with 80 daily exceedences at at least one recording station, according to preliminary information compiled by the EU-body European Environment Agency (EEA).

An EU directive on air pollution by ozone requires governments to inform the public whenever monitoring stations detect ozone concentrations above a critical threshold, set at 180 microgrammes of ozone per cubic metre of air (ug/m3) averaged over one hour. The preliminary evaluation of the April-August 2001 period shows that the public information threshold was exceeded in 16 of the 25 countries that supplied data, with an exceedance occurring in at least one of these nations on 101 of the 153 days covered.

Reflecting more frequent warm and sunny weather in summer 2001, ozone concentrations were slightly higher this year than last, the EEA says, but an in-depth analysis of data since 1994 shows a mixed trend of falling peak levels but rising average concentrations.

Smog levels tended to be highest during warm, sunny weather, and are generally higher in southern Europe than in the north. France recorded the second highest number of exceedences, when a threshold was exceeded for at least one hour on 58 days and Spain came third with 48. Governments are also required under the 1992 EU directive to issue public warnings if ozone concentrations exceed 360.25 ug/m3, averaged over one hour. During the summer period this level was reached, but not exceeded, at one monitoring station in Spain.

The EEA does stress that the figures do not necessarily give a fair comparison because of wide variations in the extent of different countries’ ozone monitoring networks. While France, Spain and Italy all have close to 300 or more stations monitoring ground-level ozone, Poland, which has a comparable size and population, only has 20 such stations. France and Belgium both had the highest proportion of stations reporting exceedances at 73%.

The average maximum ozone concentration during exceedances of the public information threshold this year was 200.25 ug/m3, with exceedances lasting on average between 1.2 hours in April and 3.0 hours in June and August.

The countries that recorded no exceedances of the public information threshold this year were Bulgaria, Denmark, Estonia, Finland, Ireland, Latvia, Lithuania, Norway and Sweden. For Ireland and Finland, 2001 marks the fourth consecutive year without exceedances. The UK was ranked joint tenth in the number of exceedences alongside the Netherlands with nine days in exceedence.

The findings suggest, on the one hand, that reductions since 1990 in emissions of the pollutants that lead to ozone formation, principally, nitrogen oxides, volatile organic compounds and carbon monoxide, are feeding through into lower peak concentrations and so reducing the European population’s short-term exposure to ozone. On the other hand, however, the increasing average concentrations of ozone, for which no unambiguous explanation exists, are increasing the public’s long-term exposure to the pollutant, says the EEA.

In a related development, agreement was reached among the EU institutions, pending final approval by the European Parliament, on a new ozone directive that will include the introduction of an “alert” threshold at 240.25 mg/m3. When ozone concentrations exceed this threshold, governments will have to implement action plans aimed at achieving an immediate reduction of ozone pollution where feasible. The EEA report finds that of the exceedances of the public information threshold recorded this year, around 5% also exceeded the future alert threshold.