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PAH pollution - state
of the art
Usually, benzo(a)pyrene is used as indicator of the total PAH
concentrations and in the 1990s, typical annual mean concentrations for BaP in
ambient air varied:
·
Between 0.1 and 1 ng/m3
in rural background areas; between 0.5 and 3 ng/m3 in urban areas
(traffic sites are included at the upper part of this range) and
·
Up
to 30 ng/m3 in the immediate vicinity of certain industrial
installations. PAH are emitted from a
number of industrial, agricultural and domestic sources, major contributors being
combustion of solid fuels (best estimate: 50 % of total benzo(a)pyrene
(BaP) emissions), and to a much lesser extent primary aluminium production (15
% in 1990) and cookeries (5 % in 1990) .
A further source is the
exhaust from road transport, i.e. from diesel engines (5 %). Important natural
sources are fires and volcanoes.
Current and in
progress legislation
There is at present no
EU or US ambient air quality limit value for PAH compounds. Some
Member States set guide or target values that are not legally binding, ranging
from 0.1 to 1.3 ng/m³ for BaP. Italy has a legally enforceable ambient air quality standard of
1.0 ng BaP/m³. Sweden also has a guidance value of 2 ng/m³ for
fluoranthene.
The draft Directive on
arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in
ambient air will not impose strict air quality limits, but foresees mandatory
monitoring where concentrations exceed 1 ng BaP /m³ (annual average).
As far as designing a
network to monitor compliance with a potential BaP limit value is concerned,
the macro-scale setting criteria described in Annex VI of Council Directive
1999/30/EC for the protection of human health are also applicable to PAH.
Focusing on urban
areas, these criteria are aimed to design the network to cover the areas with
the highest concentrations including industrial sites, traffic sites and sites
in environments where solid fuels are used for heating.
In particular, in the
case that monitoring urban hot spots, i.e. areas with high traffic
density, canyon streets, and/or areas with high usage of coal or wood for
domestic heating must be monitored, the sampling point should be representative
of an area of at least 200 m2. Furthermore, urban background
measurement points should be representative of larger parts of towns (of
several km2 ) and should not be directly
impacted by traffic, chimney stacks of domestic heating (coal, wood or oil) or
any other PAH source. Appropriate sites may be: residential areas, parks,
pedestrian-reserved areas, recreational areas or squares, yards of public
buildings (such as city halls, schools or hospitals).
Micro-scale criteria
for network positioning established for measurements of particles and benzene,
in the Directives 1999/30/EC and 2000/69/EC are applicable to PAH too (height
of the sampling inlet and its distance from vehicles stop or waits).
Reference sampling
methods
In the absence of a CEN
standardized method, the Member States are allowed to use national standard
methods. All the methods involve sampling, extraction, clean-up and analysis.
Sampling may be performed using either high or low-volume samplers, which may
collect TSP or PM10 fraction or finer fractions if available. Whilst
the particulate phase is always collected, the vapour phase is only collected
if a sorbent material is also located in the sampling train. Extraction and
clean-up methods vary widely and analysis can be performed by flame ionization
detector, mass spectrometric detector or high pressure liquid chromatography
(HPLC). |