Terms related to limit
values and assessment areas and regimes
Zones
Member States must
divide their territory into zones. This is a task done at national
level, and the local level is usually not involved in the definition of the
zones. Zones are primarily areas restricted in size, selected/defined such that
they are suitable units for air quality management. A zone should be selected
such that its AQ problems can be assessed and managed as much as possible
without having to deal with sources and emissions outside the zone in a very
detailed manner.
There are no formal
requirements as to how the Member State should specify its zones, but general principles for this,
and typical tendencies in Member States based upon practical considerations are
described in the “Guidance report”. The Member States are to report annually
the air quality situation in the zones.[d1] Zones can be large cities (agglomerations). Other types of
zones can be small (possibly as small as sections of streets), or large (region
of a country).
Agglomeration: An “agglomeration” is a special type of zone, defined as
an urban area with population exceeding 250,000. Each such agglomeration shall
be defined as a separate zone.
Practice in most MS is
to use larger administrative areas as zones, in addition to agglomerations and
in a few cases smaller urban areas which are also defined as separate zones,
when there is a risk that the LV/TVs are being exceeded in them.
Limit values and
related terms
Limit value (LV): The limit value for
a pollutant is set such that concentrations below the LV is
considered to provide adequate protection against damage to those affected by
it (people, vegetation, buildings). A "limit value" is a combination
of a concentration value (number) and an associated averaging time (e.g. hour,
day, year,...) and (for hours or days) possibly a
number of allowed exceedances per year.
Target Value (TV): This value (also a combination of a numerical value and an
averaging time) is set with the aim to avoid more long-term harmful effects on
human heath and/or the environment.
Upper assessment
threshold (UAT): A value set at about
60-70% of the LV. If the pollutant level is above UAT, certain requirements
of AQ assessment must be fulfilled in the various zones.
Lower assessment
threshold (LAT): A value set at about
40-50% of the LV. If the pollutant level is below the LAT, the requirements
to the monitoring are relaxed; assessment solely by modelling is allowed.
Alert threshold: A value for certain pollutants which represents a level of
danger to the population. If the pollutant level is above this value, the
population must be alerted without delay, for instance via radio (see Informing the public).
Margin of Tolerance
(MOT): This term describes the situation
that the pollution level must be phased down towards the LV,
as the LV is coming into force. The LV/TVs are to be met in 2005 or
2010. In the years before that, it is tolerated by the Commission that the
pollutant level exceeds the LV/TV, limited to a given “margin”, without
corrective actions being required. This margin is made successively smaller the
closer it gets to the year of attainment (2005 or 2010). If the LV+MOT
is higher than a prescribed level in a given year
before the LV must be met, the Directive requires that corrective
actions be planned.
Assessment regimes
in zones
The term
"Assessment regimes" relates to the broad types of assessment methodologies
that can be used: monitoring at different levels of accuracy; different
modelling methodologies. In the directives, it is the air pollution level in an
area, which determines which types of assessment methodologies the Commission
will accept being used for the area. This can be broadly summarised as below:
·
If the air pollution
level of a compound exceeds the UAT, monitoring at high quality with high
temporal resolution is required;
·
If the level is below
the LAT, indicative measurements, modelling and objective estimation methods
will be accepted
·
At levels between
these two thresholds, the requirements to methodologies are less strict that
when levels are higher.
Appendix 1 describes
this in more detail.
Where should the
Limit Values apply? Definition of "residential areas"
In principle, the LVs apply everywhere, except for at work places. At the
same time, a pragmatic approach to AQ management should be taken. Exceedances at places where exposure of the population (or
of ecosystems, in the case of ecosystems related LVs)
is not likely, should not be treated as rigorously as areas where exposure is
likely. An example of this is exposure to an annual average LV
in areas along a rural stretches of motorways.
The question above is
met when designing monitoring networks, and locating monitoring stations. The
1st Daughter Directive specifies that monitoring stations should be located:
·
Where a population
group is likely to be exposed to the highest concentrations that occur, for a
period which is a significant part of the averaging period of the LV;
·
So that it represents
the more general level of population exposure in the area.
In both cases, the
location of stations is based on population exposure considerations.
Local AQ administrators
may want to concentrate their monitoring in "residential areas", in
view of the importance of the exposure of the population. The definition of
"residential areas" in terms of AQ management is then that they
include all areas where a part of the population is likely to be exposed to
high and/or typical concentration levels.
Terms related to
assessments
Preliminary
assessment (PA)
This term refers to the
assessment of air quality before the Directive enters into force in order to
define zones, monitoring networks and assessment methods. If a Member State does not have sufficient information about the AQ levels
in all their zones and agglomeration, it must carry out the necessary series of
representative measurements, surveys or assessments so that they have data
available in time for the implementation of the Directives.
The Guidance Report on
Preliminary Assessment under the EU AQ Directives is an example of a source of
information on how to carry out a preliminary assessment (see the reading list
below).
Supplementary
assessment
This is the term for
methods for assessment of air pollution which are used
in addition to the measurements/monitoring of concentrations. These methods are
creating an emission inventory, indicative measurements and air quality
modelling, (which gives additional information, such as on spatial distribution
of concentrations between the monitoring stations), human exposure,
contributions from various source types, etc. This gives a better basis for
development of effective action plans. Supplementary assessment is not
mandatory; if not carried out, a higher number of stations is
prescribed. The supplementary methods, and their results, must be documented
and reported in the Annual report.
Spatial
concentration distribution
This term is new in
connection with EU AQ Directives. The assessment of AQ should now not be
limited to what is measured at the monitoring stations. The assessment should
in principle cover the whole territory, and for this purpose the so-called
"supplementary methods", such as modelling (see above) are encouraged
by the Directives.
How to assess if a
zone is in exceedance?
A zone is exceedance of an LV,
when:
·
A station in
monitoring network with suitably located stations(stations in areas with
maximum and/or typical concentration levels) measures the exceedance;
·
The assessment using
also supplementary methods (emissions, modelling) indicates that the LV
is exceeded at locations where monitors are not located.
The assessment should
also indicate the size of the population which is exposed to various levels of
concentrations above the LV.
Exemption
("derogation") for natural events and for other reasons
For PM10,
natural sources can at times contribute significantly to its concentration.
Since natural sources cannot be controlled, the Commission allows that exceedances of LV
which are caused by natural events (e.g. sand storms, suspended soil dust)
shall not be taken into account when determining whether the LV
is exceeded.
Also high PM10
levels caused by resuspension of dust from winter
sanding of roads can be exempted. These events have to documented/justified as
being caused by such events.
Terms related to
reporting
Regular reporting to
the Commission
The responsibility for
reporting to the Commission is at the national level. The local level normally
provides their data to some national database suited for further reporting to
the Commission. The following types of reports are to be prepared at the
national level for submission to the Commission (see also Topic LEG4):
Annual Report: The Annual reporting from each Member State to the Commission has the form of an official
questionnaire, to be sent in before 1 October of the following year. The
questionnaire has sections regarding zones where LV,
UAT and LAT are exceeded, reasons for individual exceedances,
on methods, etc.
Starting date: The
first Annual report to the Commission should be submitted before 1 October 2002, and concern 2001 data and assessments. Annual reports
shall be submitted for each subsequent year.
Information to the
public
This term refers to the
obligation of the administrators to keep the public up-to-date on information
on air pollution levels, as well as on the plans and programs for management
and improvement of the air quality.
The pollutant
concentration information shall be updated at least once per day. High air
pollution episodes, where Alert levels are likely to be exceeded, should be
communicated in time that the population affected have a chance to seek
protection.
Reporting on causes
of exceedances and reduction plans
This term has a bearing
on the air quality assessment regime and system that a local administrator
needs to set up. The Commission requires that causes of LV
exceedances are reported – that this represents the
basis for development of the local plans and programmes to improve the
situation.
The administrator needs
to assure that the causes can be described, and for this he will need
information about the strength of the various emission sources (an emissions
inventory), probably also air quality models as well as meteorological data
which together can be used to calculate/estimate source contributions at given
times with high concentration levels.
If the concentrations exceed the LV+MOT,
the responsible authorities must develop a ‘plan or programme’ to ensure that
the levels are brought below the limit value in time and send this to the
Commission. |