Tài liệu Ambient air pollution by Polycyclic Aromatic Hydrocarbons (PAH). Position Paper pptx

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PAH Position Paper
July 27th 2001
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PAH Position Paper
July 27th 2001
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Contents
1. INTRODUCTION, CHARACTERISATION AND CURRENT REGULATION 1
Scope of the PAH Working Group 1
Definition of PAH and their Properties 2
Current Regulations in Member States 2
2. SOURCES OF EMISSION, SINKS AND AMBIENT CONCENTRATIONS 4
Emission Inventories 5
Post Emission Effects and the choice of PAH Markers 11
Ambient Air Levels in Europe 12
3. MEASUREMENT: METHODOLOGY, ASSOCIATED UNCERTAINTY AND
FUTURE REQUIREMENTS 15
Data acquisition and monitoring network design 16
Measurement Methods 20
Modelling – General Considerations 22
Quality Assurance and Control required for PAH determination in air 24
Uncertainty of the Analytical Methods 25
4. TOXICOLOGICAL BASIS FOR LIMIT VALUE FOR PAH COMPOUNDS 27
The case for a limit value for PAH 27
Toxicological Guidance 29
Key Sources of Information 32
Toxicological mechanism and effects 33
Risk assessment 35
Limit value options 39
Toxicity to Environmental Organisms 40
5. WG FINDINGS, CONCLUSIONS AND RECOMMENDATIONS 41
Working Group Findings 41
Conclusions 44
Recommendations 47
PAH Position Paper
July 27th 2001
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PAH Position Paper
July 27
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2001
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1. Introduction, Characterisation and Current
Regulation
Scope of the PAH Working Group
1. In 1999 the European Commission, created a Working Group to review the
knowledge on polycyclic aromatic hydrocarbons (PAH) in ambient air and to
consider the need and implications of regulations on the concentrations of
PAH under the Air Quality Framework Directive (96/62/EC). Their work
entailed:
• examining the known sources of PAH emission;
• assessing existing information on PAH concentrations in the ambient air;
• assessing trends in emission and ambient levels;
• reviewing currently available measurement and assessment techniques in
relation to PAH;
• the preparation of a review of the effects of PAH;
• collating the experience of member states in the:
− assessment and management of the risks associated with PAH;
− setting air quality standards and guidelines;
• making recommendations to the Commission for air quality standards and
associated monitoring and assessment strategies.
2. The experts serving on the Working Group, whilst reflecting the concerns of
member states, industry and non-governmental organisations, formulated an
independent view based on scientific and technical consensus. A distinction
was drawn between preferred air quality objectives based on an objective risk
assessment and practically achievable ambient air concentration standards now
and in the future.
3. PAH is a term encompassing a wide range of compounds that are emitted from
a number of sources. Airborne PAH include substances which, when inhaled,
are believed to produce lung cancer in humans. The attention of the Working
Group focused on ambient air and the limited number of PAH compounds that
showed the highest evidence of human carcinogenity. Particular emphasis
was given to lung cancer as an effect demonstrated by epidemiological and
experimental studies using PAH mixtures typical of environmental exposure.
The working group agreed therefore not to consider in detail:
− exposure to PAH other than from breathing ambient air,
− PAH compounds with no evidence of human carcinogenic activity, or
which are not evaluable as human carcinogens
− carcinogenic risk from transformation products or derivates of PAH due to
interaction with other pollutants such as oxides of nitrogen.
Ingestion is an important exposure pathway, consequently eating food
contaminated with PAH from the cooking process or deposited from the air
may be a health risk but was judged to be outside the current remit of the
working group. Exposure to airborne PAH occurs both indoors and outdoors.
Indoor exposure to tobacco smoke, cooking and open fire places etc is beyond
the scope of this report – as is exposure in the work place which is covered by
regulations concerned with occupational health and safety.
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Definition of PAH and their Properties
4. PAH are a large group of compounds, they consist of two or more fused
aromatic rings made entirely from carbon and hydrogen. The physical and
chemical properties of the individual PAH vary. Some physical properties and
structures are shown in Table 1: Physical Properties and Structures of
Selected PAH.
5. Whilst the physico-chemical properties of PAH vary considerably the semi-
volatile property of some PAH makes them highly mobile throughout the
environment, deposition and re-volatilisation distributing them between air,
soil and water bodies. A proportion of PAH is subject to long range
atmospheric transport making them a transboundary environmental problem.
6. PAH are reported in many different ways. Different subsets of individual
compounds are considered for different purposes. Some currently used lists of
PAH together with the classification according to IARC, are shown in Table
2: Details of carcinogenic groups and measurement lists of PAH.
Current Regulations in Member States
7. There are currently no EU Directives or other guidance to member states
which bear directly on either emissions or air quality objectives of PAH. PAH
are, however, covered by the Persistent Organic Pollutant (POP’s) -Protocol
under the United Nations Economic Commission for Europe’s Convention on
Long Range Transboundary Air Pollution [UN ECE CLRTAP]; under the
Protocol, emissions of four PAH compounds have to be reported annually; in
addition, emissions of PAH in 2010 may not exceed the levels of 1990 (or any
other base year between 1985 and 1995). The Protocol will enter into force
after 16 ratifications, which is expected between 2001 and 2002. The
European Community is a party to the Convention and will therefore have to
fulfil the obligations of the Protocol after ratification. Of the EU member
states currently only Italy has legally enforceable ambient air standards for
PAH but five others have sufficient concern that they have issued guidance for
planning and policy purposes. All have used BaP as a marker for PAH and one
(Sweden) has gone further and set a value for fluoranthene as well. See
Table 3: Review of Legislation or Guidance intended to limit ambient air
concentrations of PAH.
8. While not directly controlling PAH it is likely that a number of Directives do,
nevertheless, indirectly influence their emission or concentration in ambient
air. These include the directives: arising from the Auto Oil programme, on the
incineration of wastes, the IPPC directive (96/61/EC), the air quality
framework directive (96/62/EC) and its first daughter directive -1999/30/EC
[Council Directive relating to limit values for sulphur dioxide, nitrogen
dioxide and oxides of nitrogen, particulate matter and lead in ambient air, OJ
L 163, 29.6.1999, p.41] which addresses particulate matter. The objectives of
this legislation can not be met without the control of the emissions of
particulate material from a very wide range of sources, many of which are
sources of PAH. It is likely that measures to meet the objectives of the
daughter directive will reduce PAH emissions also. New vehicle emissions
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regulation ('EURO IV') will, in time, further reduce particulate emissions too;
this will result in further PAH reductions. The effect of these measures is hard
to predict.
9. The World Health Organisation [WHO] has examined the issue of PAH health
risk on a number of occasions and has published Air Quality Guidelines in
1987 and 2001.
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2. Sources of Emission, Sinks and Ambient
Concentrations
Chapter Summary
General Points
• There are five major emission source components:
• Domestic,
• Mobile,
• Industrial,
• Agricultural,
• Natural.
The relative importance of these sources is expected to change with time as a result of regulations and
economic development
• Current inventories have a high uncertainty and are often not directly comparable; some address
BaP only, whilst others comprise additional compounds which are not always specified,
• Despite current uncertainties, a continued significant reduction in total mass emission from 1990 to
2010 is anticipated, predominantly in the industrial and mobile sectors; only minor reductions are
predicted for the domestic sources.

Industrial Sources
• Most important industrial sources include cokeries, primary aluminium production (in particular
plants using the Soderberg process) and wood preservation,
• Industrial sources are being increasingly regulated (e.g. through IPPC); in addition improved
energy management is leading to improved combustion.
• Total PAH emissions from industrial sources are therefore decreasing,
• BaP from industrial sources is largely associated with particles <2.5µm,
• Some industrial sources have considerable impact on local air quality, even after applying BAT.

Domestic Sources
• Emissions are predominantly associated with the combustion of solid fuels (as wood and coal),
• BaP from domestic sources is associated with a range of particle size including <2.5µm,
• Sources are numerous and widespread,
• There is no uniform European regulation,
• Improvements can be achieved using new combustion appliances and fuel switching.

Mobile Sources
• Emissions from new vehicles are regulated at a European level but not specifically for PAH,
• Emission is a function of engine type, emission control, load, age, fuel and driving mode,
including cold starting,
• There is increasing control over particles emission,
• BaP from mobile sources is largely associated with particles <2.5µm,
• Emissions are at ground level, widespread and concentrated in urban environments.



Agricultural sources
• Agricultural burning is a source of PAH which is regulated at a local level but not at a European
Level.

Natural Sources
• Natural sources such as fire, volcanoes and other PAH-producing events are stochastic; they have
not been investigated in great detail, but may contribute significantly to local PAH levels.

Post-emission transformation
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Chapter Summary
• The mass and chemical speciation of PAH-in-air changes in a number of ways following emission.
Physical and chemical removal processes, and wet and dry deposition are all important,
• PAH containing 5 or more rings (including BaP) are found predominantly in the particulate phase;
those containing 2 or 3 rings are almost entirely present in the vapour phase. 4 ring compounds are
particle-bound but have the greatest seasonal variability between phases,
• The majority of particle-bound PAH is found on small particles (< 2,5 µm),
• PAH-in-air is deposited to other media where it is degraded by a variety of mechanisms. PAH
degradation rates in other media are generally lower than those in air, with BaP retention being
greatest in the sea.
Markers
• BaP is a suitable marker due to its stability and relatively constant contribution to the carcinogenic
activity of particle-bound PAH
Ambient Information
• Comparable and consistent ambient PAH concentration data for the whole of the EU region are
sparse and do not allow a detailed analysis of either total or species-specific concentrations,
• Such data which do exist, centre on concentrations of BaP
• In the 1990's, typical annual mean levels for BaP in rural background areas vary between 0.1 and
1 ng/m
3
; for urban areas between 0.5 and 3 ng/m
3
(traffic sites are included at the upper part of
this range); and up to 30 ng/m
3
within the immediate vicinity of certain industrial installations.
Very few measurement data exist for rural communities burning coal and wood domestically;
however, these measurements suggest levels similar to those found in cities,
• Concentrations can be high close to large industrial sites and busy roads.
• There appears to be a downward trend in concentrations as a result of regulatory measures already
implemented.
Emission Inventories
10. Emission inventories are an important tool in the management of air quality.
Parties to the UN ECE CLRTAP report their emissions to the European
Monitoring and Evaluation Programme (EMEP) on a regular basis. This
activity is providing a more self-consistent European-wide PAH inventory.
Nevertheless, some further work is required to ensure full inter-comparability
– see Table 4: Emission estimates from European countries. The European
Environment Agency (EEA), via CORINAIR, its initiative for the collection
and reporting of emissions on a wide range of pollutants, has encouraged a
consistency of approach between contributing countries. More recently,
guidance for the estimation and reporting of emissions of air pollutants,
including PAH, has been provided by a joint UN ECE European Monitoring
and Evaluation Programme (EMEP) and EEA Task Force (EMEP/CORINAIR
1999).

11. There are four major anthropogenic emission source components: Domestic,
Mobile, Industrial, and Agricultural. In addition PAH can be formed naturally
as a result of uncontrolled or accidental burning. The principle sources and
their relative importance are indicated in Figure 1: Current and projected
emission of BaP [Holland et al., 2001]. The levels of emission from these
sources are changing with time as a result of regulation and economic
development. Only limited information on changes occurring in chemical and
physical composition over time is available.

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12. Other international organisations/groups carrying out activities requiring
inventories include the Global Emission Inventories Activities (GEIA) project,
GENEMIS (part of the EUROTRAC programme), OECD/Eurostat - which
collects information in their joint questionnaire, the Auto-oil II consortium and
the EU work on Environmental Cycling of Selected Persistent Organic
Pollutants (POPs) in the Baltic Region [Pacyna et al., 1999].

13. Current inventories have a high uncertainty and further work is required to
improve the reliability of the estimates. Nevertheless these PAH inventories
have allowed the identification and prioritisation of the likely main emission
sources. The picture is further complicated by the lack of consistent data for
PAH species other than BaP.

14. Emission factors are used to calculate the degree to which particular sources
contribute to the total emission of a pollutant. The largest collection of
emission factors available for PAH have been published in the USA [US EPA
1998]. It is unclear as to whether these data can be utilised in a European
context as they are often based on a limited number of samples. The factors
often exhibit a wide range of values - consequently their use can lead to
widely differing estimates of emissions from the same type of process. On the
other hand it is often difficult to compare emission measurements. The
emission measurements which are available are few in number and do not
always adequately describe the measurement method, the process, or the
abatement system to be able to extrapolate the data for other installations.
Standardized procedures are not available for reporting emission data.


Emission Sources
15. This section outlines what is currently known of sources of PAH emission,
trend information, and associated uncertainty. Individual sources of PAH are
characterised by combustion processes and by particular industrial processes
which utilise PAH-containing compounds, e.g. processing of coal, crude oil,
creosote, coal-tar and bitumen. The sources considered are industrial,
domestic, mobile, agricultural and natural.


Industrial Sources
16. In general industrial sources are comparatively well understood and are
increasingly being regulated at European level (e.g. by Council Directive
96/61/EC - IPPC). Currently these include:
− Primary aluminium production (in particular plants using Soderberg
technology)
− Coke production (e.g. as part of the iron and steel production)
− Creosote and wood preservation
− Waste incineration
− Cement manufacture
− Petrochemical and related industries
− Bitumen and asphalt industries
− Rubber tyre manufacturing
− Commercial heat and power
More comprehensive information on sources and abatement is given in Annex
3 ‘Industrial Sources of PAH Emission’. Overall PAH emissions are believed
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to be decreasing; improved energy management is leading to improved
combustion which, in turn, leads to lower emissions. Most of the particulate
based PAH is to be found associated with particles less than 2.5 µm. There are
unlikely to be PAH ‘finger prints’ which are source specific but some
industrial sources are associated with other chemical indicators (metals, other
pollutant etc). Some industrial sources will have a local impact.
Domestic Sources
17. The domestic sources of PAH which can influence ambient air quality are, in
the main, heating and cooking. Domestic heating based on the combustion of
fuels varies within Europe from the use of natural gas or liquified petroleum
gas (LPG) through paraffin and heating oils to wood, coal, peat, and brown
coal. Domestic sources of PAH are geographically widespread, and the PAH
emissions are largely unregulated. Some Member States have regulations
controlling the general emissions from some domestic heating systems (e.g.
soot, carbon monoxide).

18. Modern gas and oil burners, used for circulatory heating systems and hot
water systems, have relatively low PAH emissions. Similarly, solid fuel
systems (wood, coal, peat), which are automatically controlled and fed, are
thermally more efficient (and have lower PAH emissions) than those which
are hand fed. Abatement measures can be adopted, such as catalytic devices
which will lead to a reduction of PAH emissions.

19. PAH emissions due to the domestic combustion of solid fuels make a
significant contribution to the total PAH emission. In Sweden wood burning
has been estimated to contribute 430 kg BaP in 1994 whereas gasoline and
diesel vehicles together were estimated to contribute maximum of 320 kg BaP
[Boström et al., 1999]. There is a large geographic variation in the domestic
emissions within Europe due to the climatic differences and to the domestic
heating systems in use. In urban areas where coal, wood and peat burning is
predominant, a high proportion of the PAH ambient air concentration is
associated with these sources.

20. The burning of wood, coal and peat in open fireplaces is often for the
decorative effect in addition to the heating provided. These systems are often
hand fed, of a low thermal efficiency and potentially have high PAH
emissions. BaP from these sources is associated with a range of particle size
including the <2.5µm fraction.


Mobile Sources
21. Mobile sources are modes of transport reliant on a combustion engine. This
includes aircraft, shipping, railways, automobiles and other motor vehicles
including off-road vehicles and machinery.


Motor Vehicles (automobiles, lorries, motorcycles): Motor vehicle internal
combustion engines are generally fuelled by gasoline (petrol) or diesel fuels.
There is a relatively small proportion of vehicles which run on LPG or LNG.
PAH emissions are distributed between the vapour and the particle phase.