COMMISSION OF THE EUROPEAN COMMUNITIES 
C0M(91) 220 final 
Brussels, 24 June 1991 
Proposal for a 
COUNCIL DIRECTIVE 
CM 
AIRPOimrCN HT O0ONE 
(presented by the Commission) 
EXPLANATORY MEMORANDUM 
l. mtrodufltiûû 
Air quality problems have been tackled at Community level since the 1980s. 
Since then the presence in the air of a number of recognized pollutants 
(SOg, particulates, Pb and NOg) has been regulated. 
At the present time, however, the problem of air pollution by photochemical 
oxidants* is regarded as one of the major environmental problems of the 
turn of the oentury. 
The concentrations of photo-cxidants in general and ozone in particular 
recorded in Europe are a source of concern because they have adverse 
effects on: 
human health: causing eye irritations, headaches, respiratory 
difficulties; 
nature: slowing down or disturbing plant growth; 
materials: damaging buildings (paint, polymers, etc.). 
Ozone concentration measurement in Europe is of recent origin and is far 
from being general practice in all Member States; the measurement networks 
in place at present do not guarantee optimum and complete monitoring of the 
levels of ozone in the air; moreover, the information available does not 
allow an accurate overall assessment of the problem. Also, the mechanisms 
involved in the phenomena in question are multifarious, complex and at 
present inadequately understood. 
The Commission would therefore like to see action taken to monitor ozone, 
collect and exchange Information and inform the public Only in this way 
will it be possible to obtain a better understanding of the problem, 
formulate rational plans of action, decide upon the most suitable measures 
to be taken and identify the sources to be addressed. 
Also known as photo-oxidants. Ozone (O3) is the main jtooto-oxidant 
among all the oompounds in this category. 
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2. AOUOD to ormrnt, tfinfrocftpnlorfl pollution 
At Oommunity level a series of measures are in progress or in preparation 
to reduce emissions of a number of souroes of air pollutants and in 
particular the precursors of ozone (oxides of nitrogen and volatile organic 
oompounds). These measures oonoern both stationary souroes (large 
oombustion plants) and mobile souroes (oars/lorries). 
Given that it takes several years to Implement these measures in the 
Member States (in view of transposition times, gradual application and the 
replacement rate), it is proposed that initially the impact of these 
measures on ozone levels in Europe should be monitored. During this first 
stage, and in view of the difficulty of monitoring emissions of other 
souroes of less significant precursors, it is preferable to leave it to 
each Member State to take the initiative with regard to other emission 
reductions for other industrial sectors. These additional measures could 
be optimized during a second stage. 
3. l*wwrt«rtK1« nrwren+raMrffW nf f^ in thft *1r 
The World Health Organization (WHO) reoommends that, in order to protect 
first of all human health and then vegetation, the following values for 
O3 concentration levels in the air should not be exceeded: 
Criterion Exposure Recommended 
(hours) concentrations 
(ug/m3) 
Health 1 150-200 
8 100-120 
Vegetation 1 200 
24 65 
Growing period 60 
(100 days) 
The thresholds set in this Directive are based on these values. 
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4. ttmltnHTg «nnhftngft r^f l^nnnmtlrm «nd ramlrg «ygt/m for air 
pollution ïg o?.onft 
The ozone levels now recorded in Europe are regularly above the values 
recommended to guarantee the protection first of all of health and then of 
ecosystems; the current state of knowledge of this problem does not allow 
a date to be set from which these recommendations could be met. It would 
therefore be premature to set objective and binding limit values for ozone 
concentrations in the air at present. 
It Is, however, possible now to launch at Community level a number of 
measures designed to improve our understanding of the problem of O3 
pollution and to limit the impact on human health of episodes of heavy O3 
concentrations. The measures envisaged are as follows: 
4.1 Monitoring 
It is proposed that the Member States should set up new or supplement 
existing networks for the measurement of O5 in ambient air; a number of 
station-siting criteria set out in Annex II have to be met. 
A reference method for measuring ozone Is proposed, tut any other method Is 
permissible, subject to proof of equivalence. 
4.2 Tftrtnngft of Information, 
Some of the data collected in the context of this monitoring will be 
exchanged between the Member States and the Commission in order to pool 
Individual experience and knowledge and to provide objective information 
for a subsequent stage in the control of photochemical pollution. In order 
to limit the amount of information to be exchanged, only annual statistics 
and values in excess of the thresholds above which there is a risk for 
health or vegetation will have to be transmitted. 
4.3 KaxnlDg_S3Sj£BL 
When an ozone pollution episode occurs, it is no longer possible (because 
of the nature of the phenomena involved) to reduce concentration levels by 
reducing precursor emissions; the Directive therefore seeks to limit the 
impact of such episodes on public health by setting up publio information 
or warning systems for oases where ozone levels exceed the thresholds above 
which there is a health risk. This should enable the publio to take a 
number of precautions and preventive measures in the event of pollution 
episodes. Such a publio information procedure is also part of the new 
approach to access to information on the environment, the principles of 
which are laid down in Directive 90/313/EBC. 
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The thresholds set out in the Directive are reference levels corresponding 
to health or vegetation protection requirements in accordance with WHO 
recommendations. 
6. fiihfiflqu/arrt notion 
A second stage is already provided for in this process of combating ozone 
pollution: a further proposal setting limit values for O3 in the air, 
together with an implementation timetable, will be prepared after five 
Years of operation of the procedure envisaged in this proposal. This 
subsequent proposal could also be based on other ideas developed In 
connection with the Introduction of a new overall approach to the 
establishment of air quality Directives. That will be a two-stage 
approach: a framework DLreotive will first of all be prepared to oover 
general aspects connected with air pollution: objectives pursued, minimum 
criteria for the establishment of networks, setting of various types of 
limit values corresponding to specific objectives (statutory inspection, 
aotivation of warning system, Information, etc), frequency of transmission 
of Information; following this general Directive, specifio Directives are 
envisaged: they will oonoern specif io pollutants and will be limited tc -, 
small number of provisions (numerical concentration limit values, 
measurement methods, etc). 
_ 1 -
Proposai for a Council Directive on air pollution by ozone 
THE COUNCIL OF THE EUROPEAN CEMMONITIES, 
Having regard to the Treaty establishing the European Economio Community, 
and in particular Article 130s thereof, 
Having regard to the proposal from the Commission, 
Having regard to the opinion of the European Parliament, 
Having regard to the opinion of the Eoonomio and Social Committee, 
Whereas the 1987 fourth Community action programme on the environment1 
provides for the possibility of action on photochemical pollution, and in 
particular ozone, in view of its harmful effects and the state of knowledge 
concerning its impact on human health and the environment; 
Whereas, In order to protect human health, ozone concentrations in the air 
should be limited; whereas the scientific and technical Information 
available and knowledge of the formation and transport of photochemical 
pollutants does not make it possible at present to adopt limit values for 
those concentrations; 
Whereas, however, as ocmplete a knowledge as possible of ozone pollution 
levels is required in all Member States; 
Whereas to obtain this knowledge it is necessary to set up measurement 
stations to provide data on ozone conoentrations In the air; 
Whereas, in order to obtain comparable results, the methods used by the 
Member States to determine concentrations should be equivalent; 
Whereas, in view of the special nature of photochemical pollution, the 
reciprocal exchange of information between the Member States and the 
Commission including, once it is effectively set up, the European 
Environment Agency,2 is essential for a better understanding of the 
problem; 
1 CJ No C 328, 7.12.1989. p. 1. 
2 OJ No L 120, 11.5.1990, p. 1. 
Whereas the setting of warning levels at which precautions should be taken 
by the publio will make it possible to limit the impact of pollution 
episodes on health; 
Whereas the numerical values of these levels should be based on the 
findings of work carried out in the framework of the World Health 
Organization (WHO), In particular as regards the dose-effect relationships 
established for the pollutant in question; 
Whereas the Information collected under this Directive will make it 
possible to monitor the development of air pollution by ozone and the 
impact of national and Community provisions to reduce photochemical 
precursors and establish in the future new provisions concerning ozone and 
air quality, 
HAS ADOPTED THIS DERBCTIVE: 
Article 1 
1. The purpose of this Directive is to establish a common procedure: 
for monitoring, 
for the exchange of information, 
for warning, 
concerning air pollution by ozone in order to enable the competent 
authorities of the Member States and the Commission to obtain wider 
knowledge of this form of air pollution in the Community and guarantee 
a minimum amount of publio Information where concentration thresholds 
are exceeded and there may be a risk to human health or vegetation. 
2. For the purposes of this Directive: 
"health protection threshold" means the O3 concentration value 
given in Annex I, point 1 beyond which there is a risk to human 
health In the event of prolonged pollution episodes; 
"vegetation protection thresholds" means the O3 concentration 
values given in Annex I, point 2 beyond which there is a risk to 
vegetation; 
"warning threshold" means the O3 concentration value given In 
Annex I, point 3 beyond which there is a risk to human health in 
the event of short exposure and at which steps must be taken by the 
Member States as specified In the following articles. 
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Article 2 
Each Member State shall designate at national level a central body to 
Implement the procedure set out In Article 1 point 1, and shall 
forthwith Inform the Commission thereof. 
Article 3 
Member States shall establish measuring stations to supply the data 
necessarY for the application of this Directive. Such stations must meet 
the specifications In Annex II. 
Article 4 
1. For the measurement of O3 conoentrations, Member States shall use: 
either the reference method referred to in Annex V; 
or any other method of analysis shown to produce measurement 
results equivalent to those obtained using the reference method. 
To this end, each Member State shall designate one or more central 
laboratories responsible for evaluating the method used at national 
level in relation to the reference method. 
Furthermore, they shall organize at national level intercomparisons 
between laboratories taking part in the collection and analysis of the 
data. 
2. Once the measuring stations have been established, Member States shall 
provide the Commission with the following information: 
the method used to determine O3 concentrations and, if it is 
different from the reference method, proof of its equivalence with 
the latter; 
the geographical coordinates of the measuring stations, a 
description of the area covered by the stations, and the 
site-selection criteria; 
the results of any indicative measurement programmes carried out 
under the provisions of Annex II, point 2. 
3. The Commission may organize, on a Community scale, inteixDomparison 
programmes between central laboratories. 
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Article 5 
Member States shall make the necessary arrangements for Informing the 
public by the most appropriate means (radio, television, newspapers) 
where the warning value given In Annex I, point 3 is exceeded. The data 
to be diffused is that be found on the text contained in Annex IV. 
Article 6 
1. As from [1 January 1994], Member States shall provide the Commission 
with the following information no later than three months following the 
annual reference period: 
the maximum, the median and the 98th percentile of the mean values 
over one hour and eight hours recorded during the year in each 
measuring station; the percentiles shall be calculated in 
accordance with the method given in Annex III; 
the number, date and duration of periods during which the 
thresholds in Annex I, points 1 and 2 are exceeded. 
2. Where the warning threshold in Annex I, point 3 is exceeded, 
Member States shall inform the Commission no later than seven days 
following the period in question of: 
the date of the occurrence; 
the duration of the occurrence; 
the maximum hourly concentration recorded during this period. 
Where possible, this information should be supplemented by relevant 
data concerning sources of precursors and weather conditions which 
might explain the reasons for the occurrence. 
3. Where the data referred to in paragraphs 1 and 2 above are available in 
the Member States for periods preceding the date referred to in 
Article 9 of this Directive, Member States shall send them to the 
Commission at the latest when they send the data relating to the first 
reference period. 
Article 7 
Member States and the Commission shall regularly exchange information 
concerning: 
the data collected under this Directive; 
measures taken or planned and programmes established by the 
Member States to improve air quality; 
experience and knowledge concerning the problem of photocheml cal 
pollution. 
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Article 6 
On the basis of the information collected, the Commission shall submit to 
the Council no later than [1 July 1997] a proposal on the control of air 
pollution by O3, including in particular limit values for O3 
conoentrations in the air and time limits for compliance therewith. 
Article 9 
Member States shall bring into foroe the laws, regulations and 
administrative provisions necessary to comply with this DLreotlve no later 
than [31 December 1992]. They shall forthwith Inform the Commission 
thereof. 
When Member States adopt such provisions, they shall contain a reference to 
this Directive or shall be accompanied by such a reference at the time of 
their official publication. The procedures for making such a reference 
shall be laid down by the Member States. 
Article 1Q 
This DLreotlve is addressed to the Member States. 
Done at Brussels, 
FOr the Council 
The President 
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ANNEX I 
7ÎWftn™ff for Q7i0nft concentrations In tfo ^Tl 
(The values are expressed In ug 03/m3. The volume must be standardized 
at the following conditions of temperature and pressure: 293* K and 
101.3 kPa). 
I - Wft*ltfr protection threshold 
(Lengthy exposure) 
110 ug/m3 for the mean value over eight hours2 
2 - Vegetation protection thrfifihOld^ 
200 ug/m3 for the mean value over one hour 
65 ug/m3 for the mean value over 24 hours 
g - Health protection warning value 
(Short exposure) 
175 ug/m3 for the mean value over one hour 
1 Conoentrations must be measured continuously. 
2 The mean over eight hours is a simple moving average calculated each 
hour h from the eight hourly values between h and h-9. 
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ANNEX II 
Monitoring of ozone, concentrations. 
1. The purpose of measuring ozone concentrations in ambient air Is to 
assess • 
(1) as closely as possible the individual risk of exposure of human 
beings to values In excess of the health protection thresholds; 
(11) the exposure of vegetation (e.g. forests, natural ecosystems, 
crops) to the values given In Annex I. 
2. The measurement points shall be located at geographically and 
olimatologioally representative sites where: 
(1) the risk of approaching or exceeding the thresholds in Annex I is 
the highest; 
(11) it is likely that one of the targets mentioned in paragraph 1 is 
At places where the Member States do not have Information oonoernlng the 
sites mentioned under (i) and (11), they shall carry out indicative 
measurement programmes in order to determine the siting of the measurement 
points to supply the data necessary for the application of this Directive. 
3. Member States shall establish additional measurement points in order: 
(i) to contribute towards the identification and description of the 
formation and transport of ozone and its precursors; 
(11) to monitor changes In ozone concentrations In areas affected by 
background pollution. 
Parallel measurement of photochemical precursors (oxides of nitrogen, 
volatile organic compounds) is recommended in order to make it possible to 
identify links between the different pollutants. 
4. The final reading of the measurement Instruments must be carried out in 
such a way that the mean values over one hour and eight hours can be 
calculated, In accordance with the provisions of Annex HI. 
- 8 -
ANNEX III 
1. Concentrations must be measured continuously. 
2. The annual reference period shall begin on 1 January and end on 
31 December in any given calendar year. 
3. For the validity of the calculation of the percentiles* to be 
recognized, 75% of the possible values must be available and, as far as 
possible, distributed uniformly throughout the period In question for 
the particular measurement site. If that is not the case, this fact 
must be mentioned when the results are communicated. 
The calculation of the 50th (96th) percentile on the basis of the 
values recorded throughout the year shall be carried out as follows: 
the 50th (96th) percentile must be calculated from the values actually 
measured. The measured values shall be rounded off to the nearest 
ug/m3. All the values are to be listed in increasing order for each 
site: 
Xj JL Xg j. Xg _<. .iXfcjl - %-1-i % 
The 50th (96th) percentile is the value of k, to be calculated from the 
following formula: 
k - 0.50 (0.96).N 
N being the number of values actually measured. The value of 0.50 (0.98).K 
shall be rounded off to the nearest whole number. 
The median shall be calculated as the 50th percentile. 
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ANN BX IV 
The information set out below must be circulated on a sufficiently large 
scale as soon as possible to enable the publio to take all appropriate 
preventive protective action. 
Standard text for Informing the public 
about a high level of ozojtt In thft ajj 
Situation 
Today,1 at hrs, significant concentrations of ozone in the air 
were recorded. 
At the following measurement points: 
conoentrations in excess of 175 ug/m3 (European warning value) were 
recorded. 
The details of the recorded values are as follows: 
Station Time Concentration 
(hourly mean) 
FftTflOrtfrtii 
Since no significant change in weather conditions is foreseeable in the 
next few days, significant conoentrations can still be expected 
tani^t/tomorrow/this weekend between hrs and hrs 
or 
The most recent weather forecasts Indicate an ijaprovement in the situation 
by hrs/ within ...... days. 
Where information Is provided In newspapers a reference to the previous 
day may be added. 
- 10 -
Precautions: 
As a précaution, those people who are particularly at risk from air 
pollution (children, the elderly, people with respiratory problems, 
eto. ) should avoid unaooustomed physical effort and all outdoor 
exercise during the next hrs. 
In general, it is recommended that sustained physical effort (e.g. 
Jogging) should be avoided during this period. 
For the publio in general, it is recommended that all physical effort 
should be avoided. A number of symptoms such as eye irritations, 
headaches, respiratory difficulties and a reduction in physical 
capacities may occur.1 
This paragraph is to be added in the event of concentrations in excess 
of 350 vg/mu. 
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ANNBX V 
The reference method of analysis used to determine ozone shall be the 
chemiluminesoenoe method. This method is being standardized by the ISO. 
Once the latter has published the standard In question, the method 
described therein shall constitute the reference method. 
The following points must be taken into oonsl deration when the measurement 
methods and instruments are used by the Member States in the field: 
1. The conformity of the operating characteristics of the measurement 
instrument with those indicated by the manufacturer, in particular 
background noise, response time and linearity, must be verified in the 
laboratory. 
2. The Instrument must be totally calibrated regularly, using acLbQQ 
preconditioned standard gases. 
The potassium iodide method or the method based on gas titration using 
NO as reagent is to be used in parallel In the laboratory to analyse 
the O3 content of the standard gases and/or the accuracy and 
precision of the other methods of measurement provided for in Article 4 
(double-checking principle). 
Special care must be taken with regard to interferences inherent in the 
method and the instrument in order to optimize flow rates and guarantee 
the condition of the apparatus during the calibration procedure. 
3. In the field, the Instruments must be calibrated regularly, e.g. every 
23 or 25 hours. 
In addition, the validity of the calibration must be verified by 
regularly operating in parallel an instrument calibrated in accordance 
with paragraph 1. 
If the instrument inlet filter is changed before calibration, 
calibration must be carried out after an appropriate period of exposure 
(from 30 minutes to several hours) of the filter to ambient O3 
concentrations. 
4. The sampling head must be plaoed at least 1 m away from buildings in 
order to avoid any screening effect. 
5. The sampling head opening must be protected against rain and Insects. 
No prefllter is to be used. 
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6. Sampling must not be influenced by adjoining installations (the 
aix-oonditioning or data-transmission equipment). 
7. The sampling Une must be of inert material (e.g. glass, PTFE, 
stainless steel) which is not affected by the presence of Q3. 
It must be exposed beforehand to appropriate O3 conoentrations. 
8. The sampling line between the sampling head and the analysis Instrument 
must be as short as possible. In particular, the time taken for the 
gas volume sample to pass through the sampling line must be as short as 
possible (e.g. of the order of a few seconds in the presence of other 
reagents such as NO). 
9. Condensation In the sampling line must be avoided. 
10. The sampling line must be cleaned regularly, taking local conditions 
into account. 
11. The sampling Une must be tight and the flow rate must be inspected 
regularly. 
12. Sampling must not be Influenced by gas discharges from the instrument 
or from the calibration system. 
13. All necessary precautions must be taken to prevent temperature 
variations from producing measurement errors. 
FICHE D'IMPACT SUR LA COMPETITIVITE ET L'EMPLOI 
I. Quelle est la Justification principale de la mesure? 
Il s'agit d'initial Iser sur le pian communautaire une série 
d'actions en matière de pollution atmopshérIque par l'ozone. A 
l'heure actuelle la pollution photochImlque, à laquelle l'ozone 
contribue de manière Importante, constitue un problème sérieux; 
les concentrations en ozone observées en Europe peuvent 
présenter des risques pour la santé et la végétation. 
II. Caractéristiques des entreprises concernées. En particulier: 
Les PME ne sont pas directement concernées. 
a) Y a-t-ll un grand nombre de PME? 
b) Note t-on des concentrations dans des réglons? 
- éllglbles aux aides régionales des Etats membres? 
- éllglbles au FEDER? 
III. Quelles sont les obligations Imposées directement aux 
entreprises? 
Aucune 
IV. Quelles sont les obligations susceptibles d'être Imposée? 
Indirectement aux entreprises via les autorités locales? 
Sans objet 
V. Y a-t-ll des mesures spéciales pour les PME? Lesquelles? 
Non 
VI. Quel est l'effet prévisible? 
a) sur la compétitivité des entreprises 
aucun effet 
b) sur I'emploi 
aucun effet 
VII. Les partenaires sociaux ont-Ils été consultés? Quels sont leurs 
avis? 
Pas applicable dans le cadre de cette proposition. 
ÏSSN 0254-1475 
COM (91) 220 final 
DOCUMENTS 
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Catalogue number : CB-CO-91-271-EN-C 
ISBN 92-77-73533-3 
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