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NG GROUP ON BENZENE - European · PDF fileWorking Group on Benzene Benzene: Preface. 5 Preface...

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    September 1998COUNCIL DIRECTIVE ON


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    1.1 Benzene in the atmosphere1.2 Emissions of benzene1.3 Atmospheric chemistry and transport1.4 Benzene ambient air concentrations1.5 Current National Standards and Guidelines1.6 Summary1.7 References


    Scope2.1. Human exposure to benzene2.2 Health Effects2.3. National and other Health-based Air Quality Guidelines2.4. Evaluation of human health risks2.5. Recommendations for developing limit values2.6 Reference

    2. ASSESSMENT METHODSScope3.1 Introduction3.2 Description of monitoring methods3.3 Network design and siting criteria3.4 Other assessment techniques: air quality modelling3.5 Data quality objectives3.6 Random or continuous measurements3.7 Information on air quality to the public3.8 Upper and lower assessment thresholds3.9 Summary3.10 References

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    4 ECONOMIC ANALYSIS4.1 Introduction4.2 Results of economic analysis4.3 Discussion

    5 DISCUSSION AND FINAL RECOMMENDATIONS5.1 Summary of Chapters 1-45.2 Considerations to be taken into account in setting limit values for benzene5.3 Options for consideration5.4 Reviewing limit values

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    Council Directive onAmbient Air Quality Assessment and Management

    Working Group on Benzene



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    At the meeting of the Steering Group of National Experts on Air Quality in July1995 it was agreed that woring groups would be established to produce position papers inpreparation for development of daughter legislation under the Council Directive 96/62/ECon Ambient Air Quality Assessment and Management. The present position paper isdeveloped for Benzene by a working group with participants from Denmark, Germany,Italy, Joint Research Centre (Ispra), The Netherlands, Spain, Sweden, EuropeanEnvironmental Agency (Topic Centre for Air Quality), from Industry, from the EuropeanEnvironmental bureau and from the European Commission (DG XI). Italy is responsible forthe chairmanship and co-ordination of the Working Group. The position paper must beprepared in accordance with the recommendations from the Commission (AAQ/95/1/2)with the amendments from the meeting on 5 July 1995. It will provide a technical basis forestablishing limit values and air quality objectives over the EU territory for the protection ofhuman health, ecosystems and the environment and for achieving an effective reduction ofBenzene pollution taking into consideration costs and benefits. The position paper will bepublished as a stand alone technical paper to be used as a technical reference.

    This paper addresses air quality objectives for the outdoor ambient atmosphereand it does not address indoor air pollution, deposition or synergistic effects betweenbenzene and other pollutants. Even though parts of the population may be exposed tosignificant indoor and/or workplace benzene pollution, this is outside the scope of theDirective and will not be considered in the position paper. However, as with other commonoutdoor pollutants, benzene may be present at high concentration levels in indoorenvironments such as house interiors, inside cars and the working place. In addition,Benzene is a category one carcinogenic compound. It is not expected to present a potentialrisk of acute effects, and therefore only long term limits air quality objectives are planned.

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    Chapter 1 of the position paper describes the emission sources of Benzene inatmosphere giving some quantitative data for Europe and for other industrialised countries.Emphasis is given to the emission by vehicles, especially in urban locations where it isexpected to reach the highest concentration. Emissions are resulting from direct emissionfrom the exhausts and from the evaporation of fuels either by car or from fuel distributionand refuelling. Factors controlling the concentration levels, such as the emission rates andmeteorological factors, e.g. mixing properties of the atmosphere, are also presented. Thephysico-chemical evolution of Benzene after the emission step is also presented. It includesatmospheric chemistry of aromatic compounds related to photooxidant formation and themain processes for transport and deposition. Current air concentrations in several locationsare reviewed. They include mainly conurbation, but industrial sites and remote observationsare also reported. In order to show a decreasing trend in benzene concentration, some datarelevant to past years are included.

    The impact of Benzene on the environment and especially on human health isreported in Chapter 2. Toxicological data are examined and epidemiological studies onpopulation exposed to Benzene are presented and discussed to give the basis to assess therisk assessment as a function of exposition. Recommendations are made for a basis fordeveloping limit values.

    Chapter 3 of the position paper addresses methods and tools for themeasurements and assessment of Benzene concentrations in environments where a risk ofexposure is present. A detailed description of available instruments for the automaticmonitoring as well as manual sampling and analytical methods are presented. A networkdesign for Benzene is suggested and the inclusion of Benzene monitors in existingmonitoring stations is reviewed. Quality assurance and quality control are presented in orderto ensure data of sufficiently high reliability in terms of accuracy and sensitivity. Preliminaryassessment techniques are also presented. They are mainly based on the use of propermodels which take into account emission rates, traffic distribution and prevalentmeteorological conditions. Accuracy and reliability of existing models for Benzene arereviewed.

    Cost and benefit implications of Benzene reduction are considered in Chapter 4.Finally, Chapter 5 summarises the main points of the previous Chapters and makes finalrecommendations.

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    Chapter 1



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    1.1 - Benzene in the Atmosphere

    Benzene is an aromatic hydrocarbon with molecular formula C6H6 (PM =

    78.11). It is a colourless liquid at ambient temperature with a boiling point of 80.1 C atatmospheric pressure, and a vapour pressure of 10 kPa at 20 C and about 12.27 kPa at 25C. Benzene vapour has an "aromatic" odour and an odour threshold of 1.5 ppm (v/v). It isslightly soluble in water (1,8 g/Kg at 25 C). Benzene is a Volatile Organic Compound(VOC). This is a class of compound, which includes chemical species of organic nature suchas alkanes, alkenes, aromatics, ketones, aldehydes, alcohols and others. They arecharacterised by a vapour pressure at ambient temperature higher than 100 Pa, so that mostare found in gas phase. They are commonly present in air at concentrations ranging from afew micrograms to many hundreds of micrograms per cubic meter, depending basicallyupon the emission sources, meteorological factors, transport and photochemicalphenomena.

    Emissions of benzene to the atmosphere are due mainly combustion processesfor energy production (including motor vehicles) and domestic heating. Since fuels aredistributed from the producers to the user, evaporative processes are also responsible forthe emission of large amounts of aromatic hydrocarbons in the atmosphere.

    The world-wide industrial production of benzene is in the order of more than 15million tons per year. In 1991-93 the European production of benzene, excluding benzene inpetrol, was 5.5 million tons. The only significant natural sources of benzene are biomassburning, and brush and forest fires. However, these sources do not affect air quality indensely populated areas in the EU.

    1.2 - Emissions of benzene

    Benzene in the atmosphere is due mainly to anthropogenic sources. Naturalsources are estimated in the order of 3-5% while more than 90% are estimated to comefrom anthropogenic sources. The anthropogenic sources in Europe are distributedaccording to Table 1-I, where an estimation of different contributions to the total emissionof benzene is reported.

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    Tab. 1-I - Contribution of main anthropogenic sources of Benzene in Europe

    Sources (%)Vehicular traffic 80-85

    Petroleum Refineries 0.3-1.5Fuel Distribution 2.6-6

    Chemical Industry 1.3-13Domestic Heating 3-7

    Solvent Use 1-4

    Source: Air Quality Report of the Auto Oil Programme (data for 1990)

    The most important and significant anthropogenic sources are combustionsources, where benzene is emitted as unburned compound. However, benzene is alsoformed from the thermal degradation of other aromatic compounds. Main contributors aretraffic and other mobile sources and energy production (including industrial combustion).Emissions from traffic are the largest source. Therefore, benzene pollution is highest indensely populated areas characterised by high traffic density. Industrial activity cancontribute to ambient benzene levels, but its contribution to the total exposure is very low.

    Unfortunately, national emission data based on emission inventories may not bevery accurate, and data from different Member States may not be directly comparableowing to different classification systems and methods of calculation. The results reportedhere are therefore subject to uncertainty. Since benzene emissions from traffic are notdirectly regulated (though benzene emissions are reduced by catalytic converters), standardvenicle emission tests do not include benzene as such. In research experiments benzeneem

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