Comparative severity of
possible air quality limit
values

A comparison between EU air quality data
and
potential EU limit values.

The EU Air Quality Assessment and Management Directive (96/62/EC) was
adopted in 1996. This Directive, commonly known as the Air Quality
Framework Directive (AQFD), provides a framework and timetable for the
development of daughter directives on a range of air pollutants.

Four Position Papers have been produced by expert Working Groups which
contain recommendations on Air Quality Limit Values (AQLVs) for sulphur
dioxide (SO2), nitrogen dioxide (NO2), particulate matter (PM10) and lead
(Pb). The Commission proposes to publish these Position Papers later in
1997. Drawing upon the Position Papers, the first outline for a proposed
daughter directive covering SO2, NO2, PM10 and Pb has been presented by
DG-XI to the AQFD Steering Group Meeting (which is the senior management
group for the AQFD involving Member States, Industry and Non-Governmental
Organizations).

CONCAWE, Europia and other industry groups have been involved in
DG-XI’s AQFD Steering Group meetings, Expert Working Groups (through
UNICE), and UNICE Shadow Groups.

Recommended AQLVs are currently being translated into draft
legislation. Once incorporated in the legislation, these AQLVs will set
firm targets to be complied with by a certain compliance year. Compliance
years of 2005 and 2010 are currently under consideration. Until the
compliance date, a margin of tolerance may be allowed. This margin is
likely to decrease linearly from entry into force of the daughter
directive until the compliance year (see Figure 1).

Figure 1
It is likely that any margin of tolerance
alowed would decrease linearly in the period leading up to the
compliance year

CONCAWE has undertaken some comparisons between actual air quality data
and the proposed AQLVs to obtain a general indication of the relative
severity of the current AQLV proposals. It must be stressed that these
potential AQLVs are still subject to discussion and should not be
considered as final. The analysis has been carried out using data from the
Air Pollution Information Service (APIS) database which contains official
air quality data measured across Europe. The comparison between APIS data
and the potential AQLVs allows an assessment of the severity of these
standards using real air quality data from the recent past. This
comparison is most valid for those requirements which may apply in the
near term but it should be noted that air quality will improve in the
future. There are many emission control initiatives that will take effect
over the next few years. The number of exceedances will reduce and the
relationship between different AQLVs may also change in time. Nevertheless
the comparison does give us a useful indication, even for the year 2010.

A range of values are given in the table below which reflect the
current discussions on AQLVs and margin of tolerance for each of the four
pollutants. It should be noted that those AQLVs without an additional
margin of tolerance associated with them would come into immediate effect
on entry into force of the daughter directive (say 1997). The table also
shows the number of air quality data series examined for each pollutant
variable and the countries from which data was available for the analysis.
The final column contains information on the percentage of the data series
where exceedances occurred

* For an annual data series to exceed
the proposed requirement, the average concentration measured over the
averaging period must exceed the concentrations given in column 3 on more
occasions than allowed in column 4.

** Data from rural monitoring
stations (areas with less than 1000 inhabitants)

*** Data from rural monitoring
stations and those in areas with less than 100 000
inhabitants.

+ Note that for the 30 µg/m3AQLV,
exceedances are calculated considering NO2 measurements only and not the
combined measured concentrations of NO2 and NO. therefore, the number of
exceedances for this AQLV would be higher than
indicated.

For both SO2 and NO2, data series were examined from the years 1990–94
(each series having more than 75 per cent valid values).

The APIS Database does not include 1-hour measurement data for SO2, so
the number of exceedances could not be calculated for these
recommendations using the APIS Database.

Unfortunately data on particulate matter is not consistent within the
APIS Database. Hence the analysis was performed using data from the UK
only. UK air quality data were examined from the years 1992 to 1994. The
total number of annual data series examined was 21 (with each series
having more than 75 per cent valid values). Daily values were computed
from 1-hour data (at least 16 hours are needed to compute valid daily
values).

It should be stressed that the UK data is not likely to be
representative of all of Europe. In particular, Southern Members’ States
may have considerable difficulty in attaining the proposed AQLVs for PM10
due to natural sources of these particulates.

Lead was not
examined as exceedances are expected to be confined to a very limited
number of industrial areas due to non-petroleum industry sources.

Conclusions

Judging by actual air quality data, certain of the proposed AQLVs being
discussed are much more stringent than others. For example, according to
the APIS data, the 40 µg/m3 annual average recommended AQLV for NO2 is
significantly more stringent than the 200 µg/m3 1-hour average (at the
99.9 per cent compliance level). There are many emission control
initiatives that will come into effect over the next few years that will
help to reduce the numbers of exceedances over time. For instance, the
measures arising from the Auto-Oil Programme will make a significant
contribution to reducing emissions from vehicles. These reductions will
have an important role in lowering the number of exceedances of the AQLVs
for NO2, NOx and PM10. However, comparable emission reductions will be
required from other sources if the number of exceedances are to be
minimized. Such significant commitments will have important economic
implications.

The current proposals have been developed with considerable care by
experts in the field and with the aim of protecting health and ecosystems.
It should be noted that changing either the concentration values or the
percentile compliance associated with a proposed AQLV is likely to have a
dramatic effect on the number of exceedances. Higher percentile compliance
levels will mean an exponential increase in the number of exceedances in
Europe.

It is important to match the monitoring station locations with the
specific type of receptor to be protected by a particular AQLV. Therefore,
exceedances of AQLVs aimed at protecting a specific type of receptor (e.g.
ecosystems, human health) should only be considered non-compliances where
the monitoring data is from monitoring stations that are representative of
the exposure of that particular type of receptor over the AQLV averaging
period.

By comparing the number of observed exceedances of the AQLVs for rural
sites proposed for SO2 and NOx for different groupings of monitoring
stations representing increasingly urban locations, it can be seen that
the type of area to which the proposed relevant annual AQLVs would apply
will be crucial in determining their severity. The annual sulphur dioxide
AQLV of 20 µg/m3 and the annual NOx AQLV of 30 µg/m3 are aimed at
protecting ecosystems (not human health), therefore, they are applicable
to rural areas.

In addition, the margin of tolerance has an important role to play in
the practical implementation of the proposed AQLVs. This margin of
tolerance will provide a certain level of protection while existing,
planned and new emission controls take effect.

There is very little data available from across Europe to assess the
impact of the proposed AQLVs for particulates, rural SO2 and NOx, or for
the 1-hour SO2 proposals. The lack of data and the uncertainties
surrounding health effects (particularly for particulate matter) would
seem to suggest that compliance years should not be set for these
pollutant variables until further information can be gathered.