2.1 Introduction

According to the ozone directive, the EU Member States have to provide the following information for the annual reference period:

  • maximum, median and 98 percentile value of 1h- and 8h- average concentrations;
  • the number, date and duration of periods during which threshold values as presented in Table 1 are exceeded and the maximum concentrations recorded during each occurrence.

In addition to this annual report, Member States must inform the Commission on a monthly basis in case exceedances of the information and warning threshold values are observed. In this report only data reported on an annual basis will be considered.

Table 1. Threshold values for ozone concentrations (in µg/m3)

Threshold for Concentration averaging Period
health protection 110 8 h
vegetation protection 200 1 h
  65 24 h
population information 180 1 h
population warning 360 1 h

A group of experts from the Members States have followed the practical implementation of the Directive. Among other items this group discussed procedures for data reporting. The formats for information and data exchanges have been defined in the document "Council Directive 92/72/EEC on air pollution by ozone. Information and data exchange/formats", Doc.Rev. 11/243/95. In general terms, the requested information consists of two parts:

  1. information on stations and measurements techniques (Ozone Directive, article 4.2, indents 1 and 2);
  2. information on ozone concentration: annual statistics and threshold exceedances (Ozone Directive, article 6.1).

Based on the experiences in processing the data for the 1994 annual report, the European Topic Centre on Air Quality (ETC-AQ) provided remarks concerning data transmission and suggestions for improvement which were discussed in the Expert Group on Photochemical Pollution. Considering the increasing amount of data requiring processing, as well as to improve the transfer of data relative to the implementation of the Directive, the Commission has prepared an update (April 1996) of the data exchange format. With respect to the transfer of 1995-data, the major changes concern the transfer of additional information:

  • type of station: definition of the location of stations as recommended in the draft decision on exchanges of information;
  • altitude of stations as recommended by the Expert Group;
  • NOx and VOC data, according to Annex 2.3 of the ozone directive;
  • file names: it is recommended to define unique names for all files in order to improve the management and transfer of the data files.

2.2 Data handling

According to the Directive the requested information should have been forwarded to the Commission before 1 July 1996. On 6 August 1996 data from all Member States had been received by DGXI and forwarded to the European Topic Centre on Air Quality (ETC-AQ).

In this report the definition of the data formats as described in the above mentioned document Doc.Rev. 11/243/95 and its April 1996 amendment is used as a reference. If necessary, files were converted at the ETC-AQ for further processing.

After processing the data and calculating various exceedance statistics, the ETC-AQ prepared for each Member State tables as presented in Annex I. The Member States were requested to check these data tables and make annotations if necessary. In case information was lacking, these items were marked and the Member States were requested to provide the missing information. Member States were informed on problems encountered while processing the data. Annotations and additions to the data received before 19 August have been incorporated in this report. Feedback with Spain (incorrect address of contact person) and Italy (data have been received too late by the ETC-AQ) failed.

An overview of the data received is presented in Table 2. For 1995 information on ozone concentrations (annual statistics and/or exceedance information) has been received for 858 monitoring stations; in 1994, information was received for about 770 stations. For nearly all stations information has been submitted on measurement methods, instruments and on calibration procedures. The location of the stations and a description of the immediate and local environments of the monitoring station is less completely available. For Portugal information on 8-hourly average concentrations is lacking. Information on station characteristics (classification, information on immediate environment) is missing for France.

Information on NOx concentrations has been received from 6 Member States; 7 Member States reported on NO2 concentrations. Information on Volatile Organic Compounds (VOC) has been reported by two Member States.

Although less problems in data handling were encountered during the preparation of this report compared to the 1994-annual report, a number of remarks and practical suggestions to further optimize the quality of data transmission can be made (see Annex III).

Table 2. Overview of data received by ETC-AQ. For each item the number of Member States and the total number of stations for which data have been submitted, is indicated.

Parameter Number of Member States Number of stations
statistics / percentile values 15 844
number of exceedances of threshold values 15 812
longitudinal and latitudinal coordinates 15 855
surroundings: information on immediate environment 14 745
information on measurement method 15 831
information on calibration method 14 720
type of station (urban, rural, street or other) 14 725
altitude of the station above sea level (in meter) 15 815
town where the station is located. 15 832
NOx statistics 6 97
NO2 statistics 7 124
VOC statistics 2 11



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