Ozone is a strong photochemical oxidant which may cause serious health problems and damage to materials and crops. Human exposure to elevated levels of ozone concentrations can give rise to decreases in lung function and inflammatory responses. Symptoms observed are cough, chest pain, difficulty in breathing, headache and eye irritation. Both laboratory and epidemiological data indicate large variations between individuals in response to episodic O3 exposure, the effects seem to be more pronounced in children than in adults [1]. The world Health Organisation (WHO) recommends a 1h guide value of 150-200 µg/m3 [2] above which symptoms and damage to respiratory functions can be expected to occur.

In view of the harmful effects of photochemical pollution, the Council adopted in 1992 Directive 92/72/EEC on air pollution by ozone [3]. The Directive defined threshold values, established procedures for harmonised monitoring, for collecting and exchanging data and for information of the public when exceedances of threshold values occur.

The thresholds set by the Directive are presented in Table 1. As far as data reporting is concerned, two types of reporting can be distinguished according to Article 6 of the Directive:

  1. Exceedances of the population information and warning thresholds (date, time, duration and maximum concentration) must be reported to the Commission within one month after occurrence (data is not necessarily validated);
  2. Exceedances of all threshold values including some additional statistics (percentiles, maxima) must be provided within 6 months after the end of a calendar year (validated data).

Table 1. Threshold values for ozone concentrations set in Directive 92/72/EEC

threshold for: concentration
(in µg/m3)
averaging period (h)
health protection 110 8
vegetation protection 200 1
  65 24
population information 180 1
population warning 360 1

According to Article 7 of the Directive, the Commission prepares a report summarising all the information transmitted by the Member States at least once a year. The report for the 1995 calendar year will become available together with this document [4].

In this document a first assessment is made of the 1996 summer season, based only on the exceedances of the population information and warning thresholds for ozone, which were transmitted by the Member States after the end of each month. The report is mainly intended to provide fast feedback to the Member States on their data. It also enables the Member States to compare the levels observed in the past summer season with those observed in other Member States.



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