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Benzene

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INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

ENVIRONMENTAL HEALTH CRITERIA 150

BENZENE

This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organisation, or the World Health Organization.

Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization

First draft prepared by Dr E.E. McConnell, Raleigh, North Carolina, USA

World Health Orgnization Geneva, 1993

The International Programme on Chemical Safety (IPCS) is a joint venture of the United Nations Environment Programme, the International Labour Organisation, and the World Health

Organization. The main objective of the IPCS is to carry out and disseminate evaluations of the effects of chemicals on human health and the quality of the environment. Supporting activities include the development of epidemiological, experimental laboratory, and risk-assessment methods that could produce internationally

comparable results, and the development of manpower in the field of toxicology. Other activities carried out by the IPCS include the development of know-how for coping with chemical accidents,

coordination of laboratory testing and epidemiological studies, and promotion of research on the mechanisms of the biological action of chemicals.

WHO Library Cataloguing in Publication Data Benzene.

(Environmental health criteria ; 150)

1.Benzene - adverse effects 2.Benzene - toxicity

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3.Environmental exposure I.Series

ISBN 92 4 157150 0 (NLM Classification: QV 633) ISSN 0250-863X

The World Health Organization welcomes requests for permission to reproduce or translate its publications, in part or in full.

Applications and enquiries should be addressed to the Office of Publications, World Health Organization, Geneva, Switzerland, which will be glad to provide the latest information on any changes made to the text, plans for new editions, and reprints and translations already available.

(c) World Health Organization 1993

Publications of the World Health Organization enjoy copyright protection in accordance with the provisions of Protocol 2 of the Universal Copyright Convention. All rights reserved.

The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health

Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The mention of specific companies or of certain manufacturers' products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar

nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters.

CONTENTS

ENVIRONMENTAL HEALTH CRITERIA FOR BENZENE

1. SUMMARY AND CONCLUSIONS

1.1 Identity, physical and chemical properties, analytical methods 1.2 Sources of human exposure

1.3 Environmental transport, distribution and transformation

1.4 Environmental levels and human exposure 1.5 Kinetics and metabolism

1.6 Effects on laboratory mammals and in vitro test systems

1.6.1 Systemic toxicity

1.6.2 Genotoxicity and carcinogenicity 1.6.3 Reproductive toxicity, embryotoxicity and teratogenicity

1.6.4 Immunotoxicity 1.7 Effects on humans 1.8 Conclusions

2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS

2.1 Identity

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2.2 Physical and chemical properties 2.3 Conversion factors

2.4 Analytical methods

2.4.1 Environmental samples 2.4.2 Biological materials 3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

3.1 Natural occurrence 3.2 Anthropogenic sources

3.2.1 Production levels and processes 3.2.2 Uses

4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION

4.1 Transport and distribution between media 4.2 Environmental degradation

4.2.1 Abiotic degradation 4.2.2 Biodegradation 4.2.3 Bioconcentration 5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

5.1 Environmental levels 5.1.1 Air

5.1.2 Water

5.1.3 Soil and sediments 5.1.4 Food

5.2 General population exposure

5.3 Occupational exposure during manufacture, formulation or use

6. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS

6.1 Absorption 6.1.1 Air 6.1.2 Oral 6.1.3 Dermal 6.2 Distribution

6.2.1 Inhalation exposure

6.2.2 Oral and dermal exposures 6.3 Metabolic transformation

6.4 Elimination and excretion 6.4.1 Inhalation exposure 6.4.2 Oral exposure

6.4.3 Dermal exposure 6.5 Retention and turnover

6.6 Reaction with body components

6.7 Modelling of pharmacokinetic data for benzene 7. EFFECTS ON LABORATORY MAMMALS AND

IN VITRO TEST SYSTEMS 7.1 Single exposure

7.2 Short-term and long-term exposures 7.3 Skin and eye irritation

7.4 Reproductive toxicity, embryotoxicity and teratogenicity

7.5 Mutagenicity and related end-points 7.5.1 In vitro studies

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7.5.2 In vivo studies 7.6 Carcinogenicity

7.6.1 Inhalation studies

7.6.2 Oral and subcutaneous studies 7.7 Special studies

7.7.1 Immunotoxicity 7.7.2 Neurotoxicity 7.8 Factors modifying toxicity 7.9 Mechanism of toxicity 8. EFFECTS ON HUMANS

8.1 General population and occupational exposure 8.1.1 Acute toxicity

8.1.2 Effects of short- and long-term exposures 8.1.2.1 Bone marrow depression; aplastic anaemia

8.1.2.2 Immunological effects 8.1.2.3 Chromosomal effects 8.1.2.4 Carcinogenic effects 9. EVALUATION OF HUMAN HEALTH RISKS

9.1 General population 9.2 Occupational exposure 9.3 Toxic effects

9.3.1 Short-term and long-term exposures;

organ toxicity

9.3.1.1 Haematotoxicity; bone marrow depression

9.3.1.2 Mechanism of action and metabolism

9.3.1.3 Immunotoxicity

9.3.2 Genotoxicity and carcinogenic effects 9.3.2.1 Mechanism of carcinogenicity 9.3.2.2 Human carcinogenesis

9.4 Other toxicological end-points 9.5 Conclusions

10. RECOMMENDATIONS FOR PROTECTION OF HUMAN HEALTH 11. FURTHER RESEARCH

12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES REFERENCES

RESUME ET CONCLUSIONS RESUMEN Y CONCLUSIONES

WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR BENZENE Members

Dr D. Anderson, BIBRA (British Industrial Biological Research

Association), Toxicology International, Carshalton, Surrey, United Kingdom (Vice-Chairman)

Dr H.A. Greim, Institute of Toxicology, Association for Radiation and Environmental Research, Neuherberg, Germany (Chairman)

Dr R.F. Henderson, Inhalation Toxicology Research Institute, Lovelace

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Biomedical and Environmental Research Institute, Albuquerque, New Mexico

Dr R. Hertel, Fraunhofer Institute for Toxicology, Hanover, Germany (now at the Bundesgesundheitsamt, Berlin) Professor A.-A.M. Kamal, Ain Shams University, Abbassia, Cairo, Egypt

Dr S. Parodi, Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy

Dr R.A. Rinsky, Division of Surveillance, Hazard Evaluations and Field Studies, National Institute of Occupational Safety and Health, Cincinnati, Ohio, USA

Dr R. Snyder, Department of Pharmacology and Toxicology, Rutgers University, Piscataway, New Jersey, USA

Dr G.M.H. Swaen, Department of Occupational Medicine, University of Limburg, Maastricht, The Netherlands

Dr S.-N. Yin, Chinese Academy of Preventive Medicine, Institute of Occupational Medicine, Beijing, China

Observers

Dr M. Bird, Exxon Biomedical Sciences, East Millstone, New Jersey, USA Dr J. Gamble, Exxon Biomedical Sciences, East Millstone, New Jersey, USA

Dr J. Kielhorn, Fraunhofer Institute for Toxicology, Hanover, Germany Dr K. Levsen, Fraunhofer Institute for Toxicology, Hanover, Germany Dr G. Raabe, Mobil Research, Princeton, New Jersey, USA

Secretariat

Dr G.C. Becking, International Programme on Chemical Safety,

Interregional Research Unit, World Health Organization, Research Triangle Park, North Carolina, USA (Secretary)

Dr M. Kogevinas, International Agency for Research on Cancer, Lyon, France

Dr E.E. McConnell, Raleigh, North Carolina, USA (Rapporteur) NOTE TO READERS OF THE CRITERIA MONOGRAPHS

Every effort has been made to present information in the criteria monographs as accurately as possible without unduly delaying their publication. In the interest of all users of the Environmental Health Criteria monographs, readers are kindly requested to communicate any errors that may have occurred to the Director of the International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland, in order that they may be included in corrigenda.

* * *

A detailed data profile and a legal file can be obtained from the International Register of Potentially Toxic Chemicals, Case Postale 356, 1219 Châtelaine, Geneva, Switzerland (Telephone No. 9799111).

* * *

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This publication was made possible by grant number 5 U01 ES02617-14 from the National Institute of Environmental Health Sciences, National Institutes of Health, USA.

ENVIRONMENTAL HEALTH CRITERIA FOR BENZENE

A WHO Task Group on Environmental Health Criteria for Benzene met at the Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany, from 2 to 6 December 1991, the meeting being

sponsored by the German Ministry of the Environment. Dr R.F. Hertel welcomed the participants on behalf of the host institute. Dr G.C.

Becking, IPCS, welcomed the participants on behalf of Dr M. Mercier, Director of the IPCS, and the three IPCS Cooperating organizations (UNEP/ILO/WHO). The Group reviewed and revised the draft document and made an evaluation of the risks for human health from exposure to benzene.

The first draft was prepared by Dr E.E. McConnell, Raleigh, North Carolina, USA. Extensive scientific comments on the first draft were received from governments, research institutions, and industry; in particular: Exxon Biomedical Sciences; CONCAWE; Mobil Research;

Health and Welfare Canada; IARC; RIVM, The Netherlands; Fraunhofer Institute and Ministry of Health, Germany; National Institute of Environmental Health Sciences, National Institute of Occupational Safety and Health, and Agency for Toxic Substances and Disease Registry, USA; Department of Health, United Kingdom; and National Chemical Inspectorate (KEMI), Sweden. These comments were

incorporated into the second draft by the Secretariat.

Dr H. Greim, Chairman of the Task Group, Dr C. Pohlenz-Michel and Dr H. Sterzl-Eckert of GSF-Institute of Toxicology deserve special thanks for the time taken after the Task Group to ensure the

scientific accuracy of the final draft monograph.

Dr G.C. Becking (IPCS Central Unit, Interregional Research Unit) and Dr P.G. Jenkins (IPCS Central Unit, Geneva) were responsible for the overall scientific content and technical editing, respectively, of this monograph. The efforts of all who helped in the preparation and finalization of this publication are gratefully acknowledged.

ABBREVIATIONS

ALMS Atomic line molecular spectrometry CHO Chinese hamster ovary

FID flame ionization detection GC gas chromatography

MS mass spectrometry

SCE sister chromatid exchange SMR standardized mortality ratio S-PMA S-phenyl-mercapturic acid TWA time-weighted average

1. SUMMARY AND CONCLUSIONS

1.1 Identity, physical and chemical properties, analytical methods

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Benzene is a stable colourless liquid at room temperature and normal atmospheric pressure. It has a characteristic aromatic odour, a relatively low boiling point (80.1 °C) and a high vapour pressure, which causes it to evaporate rapidly at room temperature, and is highly flammable. It is slightly soluble in water but miscible with most other organic solvents.

Analytical methods are available for the detection of benzene in various media (air, water, organs/tissues). The choice between gas chromatography (GC) with flame ionization or photoionization detection and mass spectrometry (MS) depends upon the sensitivity required and levels of benzene expected. Detection of benzene in the workplace usually involves collection on charcoal and GC/MS analysis after desorption. Where sensitivity in the mg/m3 range is sufficient, portable direct-reading instruments and passive dosimeters are available. If greater sensitivity is required, methods to detect benzene at levels as low as 0.01 µg/m3 (air) or 1 ng/kg (soil or water) have been reported.

1.2 Sources of human exposure

Benzene is a naturally occurring chemical found in crude

petroleum at levels up to 4 g/litre. It is also produced in extremely large quantities (14.8 million tonnes) worldwide. Emissions arise during the processing of petroleum products, in the coking of coal, during the production of toluene, xylene and other aromatic compounds, and from its use in consumer products, as a chemical intermediate and as a component of gasoline (petrol).

1.3 Environmental transport, distribution and transformation

Benzene in air exists predominantly in the vapour phase, with residence times varying between a few hours and a few days, depending on environment and climate, and on the concentration of hydroxyl radicals, as well as nitrogen and sulfur dioxides. It can be removed from air by rain, leading to contamination of surface and ground water, in which it is soluble at about 1000 mg/litre.

Due primarily to volatilization, the residence time of benzene in water is a few hours, with little or no adsorption to sediments.

Benzene in soil can be transported to air via volatilization and to surface waters by run off. If benzene is buried or is released well below the surface, it will be transported into ground water.

Under aerobic conditions, benzene in water or soil is rapidly (within hours) degraded by bacteria to lactate and pyruvate through phenol and catechol intermediates. However, under anaerobic

conditions (for example, in ground water) bacterial degradation is measured in weeks and months rather than hours. In the absence of bacterial degradation benzene can be persistent. It has not been shown to bioconcentrate or bioaccumulate in aquatic or terrestrial organisms.

1.4 Environmental levels and human exposure

The presence of benzene in gasoline (petrol), and as a widely used industrial solvent can result in significant and widespread

emissions to the environment. Outdoor environmental levels range from 0.2 µg/m3 in remote rural areas to 349 µg/m3 in industrial centres with a high density of automobile traffic. During refuelling of automobiles, levels up to 10 mg/m3 have been measured.

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Benzene has been detected at levels as high as 500 µg/m3 in indoor residential air. Cigarette smoke contributes significant amounts of benzene to the levels reported in indoor air, with smokers inhaling approximately 1800 µg benzene/day compared to 50 µg/day by non-smokers.

In many countries, occupational exposures seldom exceed a time-weighted average of 15 mg/m3. However, the actual levels reported depend upon the industry studied and in some industrially developing countries exposures can be considerably higher.

Water and food-borne benzene contributes only a small percentage of the total daily intake in non-smoking adults (between about 3 and 24 µg/kg body weight per day).

1.5 Kinetics and metabolism

Benzene is well absorbed in humans and experimental animals after oral and inhalation exposures, but in humans dermal absorption is poor. Approximately 50% absorption occurs in humans during continuous exposures to 163-326 mg/m3 for several hours. After a 4-h exposure to 170-202 mg/m3, retention in the human body was approximately 30%, with 16% of the retained dose having been excreted as unchanged benzene in expired air. Women may retain a greater percentage of inhaled benzene than men. Benzene tends to accumulate in tissues containing high amounts of lipids, and it crosses the placenta.

Benzene metabolism occurs mainly in the liver, is mediated

primarily through the cytochrome P-450 IIE1 enzyme system and involves the formation of a series of unstable reactive metabolites. In rodents the formation of two putative toxic metabolites, benzoquinone and muconaldehyde, appears to be saturable. This may have important implications for dose-response relationships, because a higher proportion of the benzene will be converted to toxic metabolites at low doses than at high doses. The metabolic products are excreted primarily in the urine. Appreciable levels of the known metabolites phenol, catechol and hydroquinone are found in bone marrow. Phenol is the predominant urinary metabolite in humans and is mainly found as an ethereal sulfate conjugate until levels approach 480 mg/litre, at which time glucuronides are detected. Recent studies suggest that benzene toxicity is the result of the interactive effects of several benzene metabolites formed in both the liver and the bone marrow.

Inhaled benzene had been found to bind to rat liver DNA to the extent of 2.38 µmoles/mole DNA phosphate. Seven deoxyguanosine

adducts and one deoxyadenine adduct have been detected in rabbit bone marrow mitochondrial DNA.

1.6 Effects on laboratory mammals and in vitro test systems

1.6.1 Systemic toxicity

Benzene appears to be of low acute toxicity in various animal species, with LD50 values after oral exposure ranging between 3000 and 8100 mg/kg body weight in the rat. Reported LC50 values range from 15 000 mg/m3 (8 h) in mice to 44 000 mg/m3 (4 h) in rats.

Benzene is a moderate eye irritant and is irritating to rabbit skin after multiple applications of the undiluted chemical. No

information is available on the skin-sensitizing potential of benzene.

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Exposure of mice to benzene by inhalation results in a significant lowering of blood parameters such as haematocrit,

haemoglobin level, and erythrocyte, leucocyte and platelet counts.

Long-term exposure at high doses results in bone marrow aplasia.

Similar, but less severe, findings were noted in rats.

1.6.2 Genotoxicity and carcinogenicity

Benzene has given negative results in mutagenicity assays in vitro.

In in vivo studies, benzene or its metabolites cause both structural and numerical chromosome aberrations in humans and

laboratory animals. In addition, benzene administration results in the production of sister chromatid exchanges and polychromatic erythrocytes with micronuclei. Benzene can reach germ cells, after intraperitoneal dosing, as shown by the production of abnormalities in sperm head morphology.

Benzene has been reported to cause the production of several types of neoplasms in both rats and mice after either oral dosing or inhalation exposures. These include various types of epithelial neoplasms, e.g., Zymbal gland, liver, mammary tissue and nasal cavity neoplasms, and a few lymphomas and leukaemias.

In those inhalation studies where a positive carcinogenic response was reported, exposure levels were between 100 and 960 mg/m3 for 5-7 h/day, 5 days/week. Oral benzene doses of between 25 and 500 mg/kg body weight in mice and rats resulted in the production of neoplasms. The length of exposure was usually 1-2 years.

1.6.3 Reproductive toxicity, embryotoxicity and teratogenicity

Benzene crosses the placental barrier freely. There are no data showing that it is teratogenic after numerous experiments in

experimental animals even at maternally toxic doses. However, it has been shown to be fetotoxic following inhalation exposure in mice (1600 µg/m3, 7 h/day, gestation days 6-15) and in rabbits.

1.6.4 Immunotoxicity

Benzene depresses the proliferative ability of B- and T-cell lymphocytes. Host resistance to infection in several laboratory species has been reduced by exposure to benzene.

1.7 Effects on humans

It is known that benzene produces a number of adverse health effects. The most frequently reported health effect of benzene is bone marrow depression leading to aplastic anaemia. At high levels of exposure a high incidence of these diseases is probable.

Benzene is a well-established human carcinogen. Epidemio-logical studies of benzene-exposed workers have demonstrated a causal

relationship between benzene exposure and the production of

myelogenous leukaemia. A relationship between benzene exposure and the production of lymphoma and multiple myeloma remains to be

clarified.

The Task Group was of the opinion that the epidemiological

evidence is not capable of distinguishing between a) a small increase in mortality from leukaemia in workers exposed to low levels of

benzene, and b) a non-risk situation.

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1.8 Conclusions

It was concluded that a time-weighted average of 3.2 mg/m3 (1 ppm) over a 40-year working career has not been statistically associated with any increase in deaths from leukaemia. Because this is a human carcinogen, however, exposures should be limited to the lowest level technically feasible. Increases in exposure level to over 32 mg/m3 (10 ppm) should be avoided. Benzene and

benzene-containing products such as petrol should never be used for cleaning purposes.

Traditionally, bone marrow depression, i.e. anaemia leucopenia or thrombocytopenia, in the workplace has been recognized as the first stage of benzene toxicity and appears to follow a dose-response relationship. In other words, the higher the dose, the greater the likelihood of observing decreases in circulating blood cells.

Exposure to high benzene levels (160-320 mg/m3) for one year would most likely produce bone marrow toxicity in a large percentage of the workers and aplastic anaemia in some cases, but little effect would be expected at lower doses. Exposure to both high and low doses would be expected to produce benzene toxicity after 10 years of

continuous exposure. Thus, a high level of both bone marrow

depression and aplastic anaemia would be seen at the higher doses and some damage would also be seen at lower doses. The observation of any of these effects, regardless of the level of exposure, should indicate the need for improved control over benzene exposures.

There is no evidence of benzene being teratogenic at doses lower than those that produce maternal toxicity, but fetal toxicity has been demonstrated.

Neurotoxicity and immunotoxicity of benzene has not been well studied in experimental animals or humans.

2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS 2.1 Identity

Chemical structure:

Chemical formula: C6H6 CAS number: 71-43-2 RTECS number: CY1400000 Common name: Benzene IUPAC name: Benzene

Common synonyms: Annulene, benzine, benzol, benzole, benzol coal

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naphtha, cyclohexatriene, mineral naphtha, motor benzol, phenyl hydride, pyrobenzol, pyrobenzole

Purity: Nitration grade >99%. Benzol 90 contains

80-85% benzene, 13-15% toluene and 2-3% xylene.

Commercial grades are free of H2S and SO2

and have a maximum of 0.15% non-aromatics compounds.

2.2 Physical and chemical properties

Benzene is a naturally occurring colourless liquid at room temperature (20 °C) and ambient pressure (760 mmHg), and has a characteristic aromatic odour. The principal physical and chemical properties of benzene are shown in Table 1.

2.3 Conversion factors

1 ppm = 3.2 mg/m3 at 20 °C at normal atmospheric pressure 1 mg/m3 = 0.31 ppm

2.4 Analytical methods

This section does not provide an exhaustive list of the

analytical methods available for detecting and quantifying benzene in various media. However, those methods that are well established and have been used in studies of human exposure and in experiments on the biological effects of benzene will be described briefly.

Table 1. Some physical and chemical properties of benzenea

Physical form (20 °C) clear colourless liquid Relative molecular mass 78.11

Flash point -11.1 °C Flammable limits 1.3-7.1%

Melting/freezing point 5.5 °C

Boiling point 80.1 °C at 760 mmHg Density 0.878

Relative vapour density

(air = 1) 2.7 Vapour pressure (26 °C) 13.3 kPa Solubilities:

water 1800 mg/litre at 25 °C non-aqueous solvents miscible with most Odour threshold 4.8-15.0 mg/m3 Taste threshold (water) 0.5-4.5 mg/litre Log n-octanol/water partition

coefficient 1.56-2.15 Sorption coefficient (log Koc -

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distribution coefficient between benzene adsorbed to soil organic

carbon and benzene in solution) 1.8-1.9

a Data from: GDCh (1988), RIVM (1988) and ATSDR (1989)

The analytical methods used for the determination of benzene depend upon the media sampled and the level of sensitivity required.

In all cases proper sampling and sample storage are essential

prerequisites, particularly as microgram and nanogram quantities are often found in environmental samples.

Some of the commonly used methods for the detection of benzene in various media are summarized in Table 2.

2.4.1 Environmental samples

Methods are available for the determination of benzene in air, water sediments, soil, foods, cigarette smoke, and petroleum and petroleum products. Most involve separation by gas chromatography (GC) with detection by flame ionization (FID) or photoionization (PID) or by mass spectrometry (MS).

The measurement of benzene in air (ambient and workplace) usually involves a preconcentration step in which the sample is passed through a solid absorbent (Baxter et al., 1980; Pellizzari, 1982; Roberts et al., 1984; Clark et al., 1984b; Reineke & Bächmann, 1985; Harkov et al., 1985; Gruenke et al., 1986; OSHA, 1987; Bayer et al., 1988;

Brown, 1988a,b). Commonly used adsorbents are TenaxR resin, silica gel, and activated carbon. Preconcentration of benzene can also be accomplished by direct on-column cryogenic trapping (Reineke &

Bächmann, 1985; Holdren et al., 1985; Fung & Wright, 1986), or benzene can be analysed directly (Clark et al., 1984a; Hadeishi et al., 1985;

Bayer et al., 1988). As noted in Table 2, the limit of detection of the GC/FID or GC/PID techniques is in the low ppb (µg/m3) to low ppt (ng/m3) range whereas the GC/MS method has a limit of detection in the low ppb (µg/m3) range (Gruenke et al., 1986). Although GC/FID and GC/PID provide greater sensitivity than GC/MS, the latter is generally considered more reliable for the measurement of benzene in samples containing multiple components with similar GC elution

characteristics. Atomic line molecular spectrometry (ALMS) has been developed to monitor benzene and other organic compounds in ambient air samples (Hadeishi et al., 1985). The detection limit is 800 µg/m3 (250 ppb).

Benzene in the workplace can be measured by portable

direct-reading instruments, real-time continuous monitoring systems and passive dosimeters (OSHA, 1987) having sensitivities in the ppm (mg/m3) range. In the USA, the more sensitive procedure of

preconcentration on charcoal followed by GC/MS analysis is generally preferred (OSHA, 1987).

Benzene in aqueous media is usually isolated by the

purge-and-trap method (Brass et al., 1977; Hammers & Bosman, 1986) followed by GC/MS, GC/FID or GC/PID analysis (Harland et al., 1985;

Blanchard & Hardy, 1986; Michael et al., 1988). An inert gas such as nitrogen is used to purge the sample, the benzene is trapped on an absorbent such as TenaxR or activated charcoal, and this is followed by thermal desorption. The sensitivity of these methods is in the low to sub µg/litre range with good recoveries and precision for most methods.

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Table 2. Analytical methods for the determination of benzene

Sample Preparation Analytica

Air silica gel trap indicator Air charcoal trap, CS2 desorption GC/FID Air (ambient) Tenax GC sorbent, thermal desorption capillary computer Air Tenax GC trap, thermal desorption, C/FID/MS cryogenic focusing

Air (ambient) direct injection GC/PID Air direct analysis UV Spect.

Air Tenax or cryogenic trap, thermal desorption GC/FID Air near landfills/ Tenax GC trap, thermal decomposition GC/FID/EC waste sites

Air silica gel trap, thermal desorption GC/MS Air (ambient) cryogenic trap, thermal desorption GC/PID GC/FID Air (ambient) charcoal trap (badge or tube, desorb with GC/FID CS2

Air solid sorbent trap, thermal desorption GC/MS Air (occupational) activated charcoal sorbent, CS2 desorption GC/FID

Table 2 (contd).

Sample Preparation Analytica

Air (occupational) porous polymeric sorbent, thermal desorption GC/FID Water (drinking) purge and trap GC/MS Water (surface or helium purge, Tenax GC trap, thermal GC/MS effluents) desorption

Water purge with inert gas, Tenax trap, thermal GC/MS desorption

Water N2 purge, Tenax GC trap, thermal desorption GC/FID Water filter through silicone polycarbonate GC/FID membrane into inert gas stream

Water purge with inert gas, Tenax trap, thermal HRGC/MS

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desorption to on-column cryogenic trap

Soil N2 purge, Tenax GC trap GC/FID Soil N2 purge, Tenax trap, thermal desorption GC/FID Sediment N2 purge, Tenax trap, thermal desorption GC/MS Mainstream filter smoke and direct to GC/MS; for HRGC/MS cigarette smoke passive smoke collect air in cryogenic

methanol-filled impingers

Jet fuel fumes sample on charcoal, methylene chloride, HPLC/UV ethyl acetate desorption; column elution

with acetonitrile

Table 2 (contd).

Sample Preparation Analytica

Blood N2 purge, Tenax GC-silica gel trap GC/MS Blood extract with toluene, centrifuge; analyse GC/FID toluene layer

Blood add heparinized sample to isotonic saline HRGC/PID in headspace via equilibrate with heat

Breath collect on Tenax GC, thermal desorption HRGC/MS Breath collect on Tenax GC, thermal desorption into GC/MS on-column cryogenic trap

Urine extraction GC/MS

Urine (phenol enzyme and acid digestion; ethyl ether GC/FID and conjugates) extraction

Urine (muconic sample mixed with methanol, centrifuge, HPLC/UV acids) analyse supernatant, elute with methanol -

acetic acid

Tissues add butyl hydroxytoluene to buffered homo- RID-HPLC/

genate, centrifuge, analyse supernatant

a GC = gas chromatography; FID = flame ionization detection; PID = photoio HRGC = high resolution (capillary) gas chromatography; RID = reverse iso UV = ultraviolet detection

b NR = not reported

Benzene in soil, sediment and food samples is usually determined by purge-and-trap methods (Harland et al., 1985; Ferrario et al., 1985; Hammers & Bosman, 1986), with headspace analysis (Kiang & Grob, 1986) and liquid extraction (Kozioski, 1985) techniques being used less frequently. Detection limits as low as 1 ng/kg have been

reported after GC/FID or GC/MS analysis, but recoveries and precision are frequently low.

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Methods have been reported for the analysis of benzene in other environmental media such as cigarette smoke (Brunnemann et al., 1989, 1990) and in petroleum products such as petrol (gasoline) (Poole et al., 1988; Dibben et al., 1989).

2.4.2 Biological materials

Benzene levels in exhaled breath, blood, and body tissues have been analysed by GC/FID, GC/PID or GC/MS, and benzene metabolites in urine have been measured using GC/FID and high-performance liquid chromatography (HPLC) with ultraviolet detection.

Prior to analysis, breath samples are usually collected on a solid sorbent such as activated charcoal, silica gel or TenaxR GC and thermally desorbed (Wallace et al., 1985; Pellizzari et al., 1988). Headspace analysis has also been used to analyse levels of benzene in exhaled breath (Gruenke et al., 1986). Greater selectivity is achieved if capillary columns are used for high-resolution gas chromatography (HRGC) (Pellizzari et al., 1988).

Three methods have been used to extract benzene from blood, i.e.

purge-and-trap (Antoine et al., 1986), headspace analysis (Gruenke et al., 1986; Pekari et al., 1989) and solvent extraction (Jirka &

Bourne, 1982). Sensitivity for the first two procedures is in the sub to low µg/litre range, whereas solvent extraction is less sensitive (low to mid µg/litre).

Total phenolic metabolites of benzene have been determined in urine following hydrolysis, extraction with ethyl ether and GC/FID analysis (Buchet, 1988). The technique of HPLC/UV has been used to determine the trans, trans-muconic acid metabolites of benzene in urine (Inoue et al., 1989). A more sensititive GC/MS method to monitor muconic acid in the urine of exposed workers has been

developed by Bechtold et al. (1991). Biological monitoring methods using urine measure concentrations of phenolic conjugates, the major metabolites of benzene (Buchet, 1988). Such methods, however, lack adequate specificity and sensitivity for low levels of benzene

exposure. A method based on the determination of the minor metabolite S-phenyl-mercapturic acid (S-PMA) appears to overcome these

deficiencies (Stommel et al., 1989). Benzene and its organic-soluble metabolites have been determined quantitatively in rodent tissues using GC/MS and reverse isotope dilution (RID) combined with semipreparative HPLC/UV (Bechtold et al., 1988). A method using ion-pairing HPLC was used to analyse water-soluble metabolites of benzene in liver and in urine (Sabourin et al., 1988).

Schrenk & Bock (1990) have developed an HPLC method for the determination of metabolites secreted by isolated hepatocytes.

Brodfuehrer et al. (1990) have reported on the determination of benzene metabolites in liver slices of rat, mouse and man.

3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

Benzene is released to the environment from both natural and man-made sources, the latter accounting for the major part of the emissions.

3.1 Natural occurrence

Benzene is a naturally occurring organic compound. It is a component of petroleum (1-4%) (IARC, 1989) and can be found in sea water (0.8 µg/litre) in the vicinity of natural deposits of petroleum

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and natural gas (Reynolds & Harrison, 1982).

3.2 Anthropogenic sources

Major anthropogenic sources of benzene include automobile

exhaust, automobile-refuelling operations and industrial emissions.

Automobile exhaust probably accounts for the largest anthropogenic source in the general environment. Cigarette smoke, off-gassing from building material and structural fires all lead to increased

atmospheric benzene levels. People are exposed to benzene mainly through the inhalation of contaminated air, particularly in areas of heavy automobile traffic and around gasoline (petrol) stations and other facilities for storage and distribution of petrol, and through tobacco smoke from both active and passive smoking (ATSDR, 1991).

Other sources of exposure have been reported to include industrial emissions and consumer products (Wallace et al., 1987). However, certain individuals may be exposed to potentially high concentrations of benzene in drinking-water as a result of seepage from underground petroleum storage tanks, landfills, waste streams, or natural gas deposits (ATSDR, 1991). Individuals employed in industries that produce or use benzene or benzene-containing products are probably exposed to much higher levels than the general population. Industrial discharge, landfill leachate, and disposal of benzene-containing waste are also anthropogenic sources.

3.2.1 Production levels and processes

Benzene ranks sixteenth in production volume for chemicals produced in the USA, with an estimated production of 4.39 x 105

tonnes (1.6 x 109 gallons) in the USA in 1991 (ATSDR, 1991) and 1480 x 103 tonnes in western Europe in 1986 (GDCh, 1988) (Table 3). In the USA over 90% of the benzene produced is derived from petroleum sources (ATSDR, 1991), i.e. refinery streams (catalytic reformates), pyrolysis of gasoline, and toluene hydrodealkylation. In western Europe 55% of the benzene production is from gasoline pyrolysis, 10%

from coking of coal, and the remaining production is divided approximately equally between catalytic reformate and the hydrodealkylation of toluene (GDCh, 1988).

Table 3. World production of benzene in thousands of tonnes for 1981a

Capacity Production

North & South America (total) 9350 6150

Asia (total) 3550 2460

Western Europe (total) 6950 3800

Eastern Europe (total) 5840 2340

Japan 2880 2060

USA 8030 5190

USSR 3250 1700

Other countries 100 50 World 25 800 14 800

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a From: RIVM (1988)

Benzene in petrol is not included.

Given the high production volume, widespread use, and physical and chemical properties of benzene, there is a high potential for large amounts to be released to the environment. However, accurate data on the amounts released are difficult to obtain. The data in Table 4 are given to show the relative amounts of benzene released to the air from various industrial sources in several countries. It is evident that the largest amounts released are from the use of

gasoline. In California (USA), the 1984 benzene emission inventory totalled 17 500 tonnes (Allen, 1987), with motor vehicle exhaust accounting for 71% of this amount. Total emissions of benzene from industrial sources within the USA have been reported to be 33 000 to 34 000 tonnes (US EPA, 1989). Recent emission data related to

automobile use in the USA are difficult to obtain, but in 1980 such emissions were between 40 000 and 80 000 tonnes (IARC, 1982). In Germany approximately 80% of the air emissions reported are due to the use of motor vehicles, whereas coke ovens account for 3.9% of such emissions. Other sources are gasoline storage and transport (6.2%) and industrial furnace emissions (4.0%).

Table 4. Major emissions of benzene into the atmosphere in tonnes per ye

Road traffic Refineries Remaining Total sources

Belgium/Luxembourg 4950 60 750 5760 Canada 25 895 654 7601 34 150 Denmark 2600 10 390 3000 France 30 000 200 4000 34 200 Germany (FRG) 62 000 200 11 000 73 200 Greece 4700 30 700 5430 Ireland 1650 0 200 1850 Italy 29 000 190 4200 33 390 Netherlands 7300 80 980 8360 United Kingdom 29 000 150 4200 33 350 European Community

(total) 171 200 920 26 420 198 540

a From: RIVM (1988). Calculated using crude oil consumption figures from 19 3.2.2 Uses

Benzene has a large number of industrial, commercial and

scientific uses. Approximately, 10% of the total use of benzene is in gasoline (RIVM, 1988), where levels average < 1% by weight in the USA (US EPA, 1985) and 2.5-3.0% v/v in western Europe (GDCh, 1988).

Along with other aromatic compounds, benzene is important in the

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production of organic chemicals, particularly styrene (Table 5). The major uses of benzene as a chemical intermediate are summarized in Table 5. There are no data indicating a major deviation from this pattern of use, which was reported in 1981.

Table 5. Industrial uses of benzene in 1981. Benzene in petrol has not been incorporateda

Production of: USA Japan Western Netherlands Europe

Ethylbenzene/styrene 51.1 50.4 48.6 73 Cumene/phenol 20.6 12.1 19.3 16 Cyclohexane 13.8 25.6 13.4 11 Alkylates 3.0 3.7 5.2 - Maleic acid anhydride 2.8 2.5 3.3 - Nitrobenzene/aniline 5.3 - 6.7 - Chlorinated benzenes 2.6 5.7 2.0 - Other products 0.8 - 1.5 -

a From: RIVM (1988). Data shown as a percentage of the total benzene consumed in each area.

In the past, benzene was used widely as a solvent, but this use is declining in most developed countries; it represents < 2% of current use. However, it is still used as a solvent in scientific laboratories, industrial paints, rubber cements, adhesives, paint removers, degreasing agents, production of artificial leather and of rubber goods, and in the shoe industry (Mara & Lee, 1978; Windholz et al., 1983; Gilman et al., 1985). For many solvent uses, benzene has been replaced by other less toxic organic solvents. However, in the past significant human exposure occurred when benzene was used as a paint stripper, a carburettor cleaner, in the production of denatured alcohol and rubber cements, and in arts and crafts supplies (Young et al., 1978). It has also been reported that benzene vapours could be detected from such products as carpet glue, textured carpet, liquid detergent and furniture wax (Wallace et al., 1987).

4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION 4.1 Transport and distribution between media

Benzene is released into the environment from both natural and man-made sources, although the latter are the most significant. The volatility and solubility are the most important properties which influence its environmental transport (see Table 1). Benzene enters the atmosphere from direct emissions and volatilization from soil and water surfaces.

The high volatility of benzene (vapour pressure of 13.3 Kpa at 26 °C), its solubility in water (1800 mg/litre at 25 °C) and a Henry's law constant of 5.5 x 10-3 atm/m3 per mole at 20 °C suggest that

benzene will partition to the atmosphere from surface water (Mackay &

Leinonen, 1975). These authors have calculated a t´ in water of 4.8 h (1 metre deep at 25 °C). Benzene in air is fairly soluble in water

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and is removed from the atmosphere by rain (Ogata & Miyake, 1978).

However, once it has been deposited on soil or water, volatilization will return a portion back to the atmosphere.

Benzene is not expected to adsorb to bottom sediments for several reasons: (1) the Koc (soil/organic carbon sorption coefficient)

(Table 1) does not predict adsorption to particles; (2) the solubility of benzene in water, and (3) the volatility of benzene.

Benzene released to soil can partition to the atmosphere through volatilization, to surface water through run-off, and to ground water if released well below the surface. Evaporation from surface soil is expected to be rapid (Hine & Mookerjee, 1975). With a Koc of 60-83, benzene is considered fairly mobile in soil (Kenaga, 1980; Karickhoff, 1981). Leaching of benzene into ground water from soil is influenced by several parameters including type of soil (sand versus clay), amount of rainfall, depth of ground water and extent of benzene degradation.

4.2 Environmental degradation

4.2.1 Abiotic degradation

In air benzene exists predominantly in the vapour phase (Eisenreich et al., 1981). Degradation of benzene in air occurs mainly by reactions with hydroxy, alkoxy and peroxy radicals, oxygen atoms and ozone, of which the reaction with hydroxy radicals is the most important. The rate constant for the reaction has been measured often (Tully et al., 1981). Assuming an average hydroxy radical concentration of 1.25 x 106 molecules/cm3 and a rate constant of 1.3 x 10-12 cm3/molecule per second, a t´ of 5.3 days was

calculated for benzene (RIVM, 1988). In areas of high traffic density where there is a higher concentration of hydroxy radicals (1 x 108 molecules/cm3) and increased levels of NOx, the 24-h average t´

for benzene has been reported as 3-10 days (GDCh, 1988). Under these conditions phototransformation products may include phenol,

nitrobenzenes, nitrophenol and various ring-opened dicarbonyl

compounds (Bandow et al., 1985). Direct photolysis of benzene in the troposphere is unlikely since the UV-visible spectrum of benzene shows no appreciable absorbance at wavelengths longer than 260 nm

(Bryce-Smith & Gilbert, 1976). This hypothesis was supported by Korte & Klein (1982). No degradation was seen after 6 days irradiation of benzene in the laboratory with light of wavelength longer than 290 nm.

4.2.2 Biodegradation

Benzene in surface and ground water is biodegradable by a variety of microorganisms under both aerobic and anaerobic conditions (RIVM, 1988). Under both conditions the mechanism of biodegradation seems to involve the formation of catechol via cis-1,2-dihydroxy-

1,2-dihydrolbenzene followed by ring cleavage (Högn & Jaenicke, 1972;

Korte & Klein, 1982).

Karlson & Frankenberger (1989) studied the aerobic biodegradation of benzene in ground water utilizing a mixed bacterial culture

containing petroleum-degrading bacteria from ground water and soil bacteria capable of using gasoline as a sole carbon source. Under closed agitated conditions without added nutrients, benzene levels dropped from 480 µg/litre to 218 µg/litre in 48 h. However, when nitrogen was added the reaction was much more rapid, with benzene levels decreasing to 35 µg/litre in 20 h. The biodegradation of benzene in ground water and river water appears to follow first-order

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rate kinetics, with t´ values of 28 and 16 days, respectively, having been reported for ground water and river water (Vaishnav &

Babeu, 1987).

Korte & Klein (1982) studied the fate of benzene on soil

utilizing composting waste. Of the benzene applied to the waste only 2-2.5% remained in situ whereas 35% volatilized. These authors

concluded that benzene does not usually remain on soil long enough for biodegradation to play an important role in its removal. A model developed to predict the environmental fate of benzene following

losses of gasoline from underground tanks indicated that approximately 1% of the benzene would be degraded (Tucker et al., 1986).

Benzene is not usually biodegradable under anaerobic conditions (GDCh, 1988). However, Wilson et al. (1986) using samples of landfill leachate showed under methogenic conditions in an anaerobic glove-box that, although no significant benzene biodegradation occurred during the first 20 weeks of incubation, after 40 weeks benzene

concentrations were reduced by 72%. Using anaerobic digesting sludge, Battersby & Wilson (1989) examined the degradation of benzene under methanotrophic conditions. Benzene, at a level of 50 mg carbon/litre, remained undegraded after 11 weeks of digestion. Although it is

slowly degraded under anaerobic conditions, benzene levels in sewage influents up to 6 mg/litre do not affect sewage treatment processes using activated sludge systems (Bennett, 1989). Jackson & Brown

(1970) reported no toxic effects of benzene on the anaerobic digestion of sewage sludges until levels of between 50 and 200 mg/litre had been reached.

4.2.3 Bioconcentration

Benzene is not expected to bioconcentrate to any great extent in aquatic or terrestrial organisms given the reported values for log Pow (octanol/water) of 2.13 and for bioconcentration factor (BCF) of 24 (Miller & Wasik, 1985). The BCF for freshwater algae was reported to be 30 (Geyer et al., 1984), for water fleas ( Daphnia sp.) it was 153-225, depending on the concentration of benzene in their food, and for goldfish it was 4.3 (Ogata et al., 1984).

5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE 5.1 Environmental levels

5.1.1 Air

Examples of benzene concentrations in urban and rural areas are given in Table 6. Daily median benzene air concentrations in the USA have been reported as: remote areas, 0.51 µg/m3 (0.16 ppb); rural areas, 1.50 µg/m3 (0.47 ppb); and urban/suburban areas, 5.76 µg/m3 (1.8 ppb) (Shah & Singh, 1988).

The concentration appears to depend largely on the density of automobile traffic and local weather conditions (Wallace, 1989a).

Although the median level in USA urban areas is 5.76 µg/m3 (1.8 ppb) (Shah & Singh, 1988), levels as high as 112 µg/m3 (35 ppb) have been observed (US EPA, 1987). Maximum levels of 510 µg/m3 (Wallace et al., 1985) and 210.6 µg/m3 (Singh et al., 1982) have been reported in two cities in the USA. In addition to the concentrations of benzene shown in Table 6, the following levels of benzene have been reported in the urban air of European cities: London, 10-12 µg/m3 background and 28-31 µg/m3 kerbside (Bailey & Schmidl, 1989);

Hamburg, Elb Tunnel, 80.5-95.3 µg/m3 (Dannecker et al., 1990) and a

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residential site 9.3 µg/m3 (Bruckmann et al., 1988); and Stockholm, average values of 147.7 µg/m3 on a busy street in the city centre and 7.7 µg/m3 on a quiet street in the city centre (Jonsson et al., 1985). Country wide averages in Germany have been reported to be 1-10 µg/m3 (0.31-3.1 ppb) (GDCh, 1988) and in three urban areas of Canada they were 2.9-19.6 µg/m3 (0.9-6.0 ppb) (Government of Canada, in press). Benzene levels, along with other pollutants, may increase during periods of still air.

Concentrations of benzene in the atmosphere of cities where chemical factories use or produce benzene are more variable. In the USA, benzene concentrations have been shown to vary between 0.4 and 16 µg/m3 (Pellizzari, 1982). Levels of 3.2 mg/m3 (1 ppm) have been

measured in the breathing zone during the refuelling of automobiles (Bond et al., 1986a).

In Frankfurt, Germany, the highest benzene levels have been measured in the vicinity of coke ovens (maximum, 166.2 µg/m3; average, 57.2 µg/m3), near industrial refineries (maximum, 102 µg/m3; average, 13.4 µg/m3), and in congested traffic areas (maximum, 171.8 µg/m3; average, 16.9 µg/m3) (GDCh, 1988).

It has been reported that people living near petrochemical plants in New Jersey, USA, have no greater exposure to benzene than the

general population throughout the area (Wallace et al., 1985). Of particular interest in this study was the observation that in Bayonne, New Jersey, benzene levels (arithmetic means) in indoor air (29.7 µg/m3) were greater than those reported for outside air (8.6 µg/m3) (Table 6).

Table 6. Examples of the concentrations of benzene measured in air

Concentration (µg/m3)

Location (year) Mean Maximum Reference

Montreal, PQ, Canada (1984-1986) 18.6 81.8 Dann (1987) Toronto, ONT, Canada (1984-1986) 9.1 37.8 Dann (1987) Houston, TX, USA (1980) 18.8 122.9 Singh et al.

Elizabeth & Bayonne, NJ, USA 8.6 91 Wallace et a (outdoor air) (1981) (1985) Elizabeth & Bayonne, NJ, USA 29.7 510 Wallace et a (indoor air) (1981) (1985) Pittsburgh, PA, USA (1981) 16.3 210.6 Singh et al.

Oslo, Norway (1980) 40 114 Wathne (1983 Rhine area, Germany (1983) 4.6-22.4 - Bruckmann et (1983) Black Forest, Germany (1983) 2.0 - Bruckmann et (1983)

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London, England (1983) 23 85 Clark et al.

England (1983) (45 km from London) 6 16 Clark et al.

Bilthoven, Netherlands (1982-1983) 2.8 10.4 RIVM (1988)

The principal source of benzene detected in indoor air appears to be cigarette smoke, making active smoking and exposure to passive smoke important sources of exposure to benzene for the general population. The mainstream cigarette smoke from one cigarette contains between 6 and 73 µg of benzene (Brunnemann et al., 1989).

Benzene has been found at higher levels in the homes of smokers (16 µg/m3) than those of nonsmokers (9.2 µg/m3) during the autumn and winter, whereas levels in the summer were comparable in both domiciles (4.8 and 4.4 µg/m3, respectively) (Wallace & Pellizzari, 1986). Levels of benzene in a smoke-filled bar in the USA were found to be 26 to 36 µg/m3 (Brunnemann et al., 1989).

Preliminary studies have indicated the release into indoor air of low levels of benzene from consumer products such as adhesives,

building materials and paints (Wallace et al., 1987).

5.1.2 Water

Rain water in the United Kingdom has been found to contain benzene levels as high as 87.2 µg/litre (Colenutt & Thorburn, 1980) (Table 7).

Concentrations as high as 330 µg/litre have been found in contaminated well water on the east coast of the USA (Burmaster, 1982). Benzene levels in open ocean samples from the relatively unpolluted waters of the Gulf of Mexico were found to be 0.005-0.015 µg/litre (Sauer, 1981) and in polluted waters levels were 0.005-0.04 µg/litre (Sauer, 1981).

Representative concentrations of benzene in various sources of water are given in Table 7.

Benzene concentrations in fresh surface waters are generally less than 1 µg/litre. In the USA, early studies reported 1-7 µg/litre in polluted areas (Ewing et al., 1977) whereas McDonald et al. (1988) reported levels of between 0.004 and 0.91 µg/litre in river water taken downstream from a chemical plant. Levels between 0.2 and 0.8 µg/litre were reported in the River Rhine in 1976 (Merian & Zander (1982). In Japan, a survey of 112 water samples revealed benzene in only 19 of the samples at levels varying from 0.03 to 2.1 µg/litre (Environment Agency, Japan, 1989).

The limited data available indicate that benzene concentrations in drinking-water are also in the µg/litre range. Otson (1987) reported that levels in 10 drinking-water supplies in Canada did not exceed 1 µg/litre. At a detection limit of 0.1 µg/litre, benzene was found in 13, 3 and 2 out of 14 samples of treated water in the summer, winter and spring, respectively. Previously, Otson et al. (1982) had reported detectable (> 1 µg/litre) levels of benzene in 50 to 60% of samples taken, the mean concentrations varying between 1 and 3

µg/litre. In the USA, water from contaminated wells contained 30 to 330 µg benzene/litre. In the same area, most samples of

drinking-water taken from surface sources had non-detectable

concentrations of benzene, and a maximum level of 4.4 µg/litre was detected (Burmaster, 1982).

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5.1.3 Soil and sediments

In general, soil contamination does not lead directly to

significant levels of human exposure because of rapid volatilization to air. Benzene in soil is usually the result of direct contamination by spillage or leakage. It has been found at levels ranging from < 2 to 191 µg/kg in soils in the vicinity of five industrial

facilities using or producing benzene in the USA (Fentiman et al., 1979). Soil concentrations in the Netherlands are low, the measured concentrations being less than those found in ground water,

i.e. < 0.005 to 0.03 µg/litre (RIVM, 1988).

Benzene was detected in 37 out of 98 bottom sediments in Japan at levels ranging from 0.5 to 30 µg/kg (Environment Agency, Japan, 1989).

In Lake Pontchartrain, Louisiana, Ferrario et al. (1985) reported sediment levels of 8 to 21 µg/kg wet weight. Between 1980 and 1982, benzene was detected in 9% of the sediment samples taken from 335 observation sites in the USA, the median level being < 5 µg/kg (Staples et al., 1985).

Table 7. Levels of benzene in water

Source Location Concentration (µg/litre) Commen

Rainwater United Kingdom 87.2 appear Germany (Berlin) 0.1-0.5 Surface water USA (Brazos River, 0.004-0.9 downri TX)

USA (13 sampling 1-13 both u locations) indust USA (Potomac River) < 2 detect Switzerland (Lake 0.03 Zurich)

United Kingdom > 7.2 (98.4 maximum) averag (80 water bodies for all samples 0.1 µg across UK)

Netherlands < 0.1 sampli (Rhine River)

Germany < 0.1-1 occasi

Table 7 (contd).

Source Location Concentration (µg/litre) Commen

Sea water Gulf of Mexico 0.005 to 0.015 unpoll during

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USA (Brazos River 0.004-0.2 flows estuary, TX)

Atlantic Ocean 0.06 x 10-3 open s Baltic Sea 0.1-4.6 x 10-3 open s Drinking-water USA 0.1 to 0.3 Canada (Ontario) < 0.1 to 0.2 10 tre Germany < 0.1-1 occasi Ground water USA (Nebraska) 1.6 (median) 63 pri 1.8 (maximum) contai Germany 0.02-0.05 USA (New York, New 30-300 contam Jersey, Connecticut)

Netherlands 0.005-0.03 unpoll

5.1.4 Food

Data on the occurrence of benzene in food are limited. However, early studies reported low levels of benzene in a variety of foods.

Some of the higher levels have been reported in Jamaican rum (120 µg/litre), irradiated beef, (19 µg/kg), heat-treated canned beef (2 µg/kg) and eggs (500-1900 µg/kg) (IARC, 1982). Other foods where it has been found but not quantified include haddock fillet, dry red beans, blue cheese, cheddar cheese, cayenne pepper, pineapple, roasted filberts, cooked potato peels, cooked chicken, hothouse tomatoes, strawberries, blackcurrants, roasted peanuts, soybean milk and codfish (Chang & Peterson, 1977). Benzene was detected at levels of 220 and 260 µg/kg wet weight in one sample of clams and oysters from Lake Pontchartrain in Louisiana, USA (Ferrario et al., 1985). These findings were not repeated when a second sample was analysed.

Benzene was detected in 37 out of 114 samples of fish in Japan within the range of 3-88 µg/kg (Environment Agency, Japan, 1989).

Gossett et al. (1983) reported that livers of marine fish caught in polluted waters near Los Angeles, USA contained levels of benzene in the range 15-52 µg/kg.

5.2 General population exposure

Benzene is ubiquitous in the environment. Most of the general population is exposed to benzene through a variety of sources. The most important source of exposure for the general population is through breathing air contaminated from man-made sources (including cigarette smoking), with inhalation exposures accounting for more than 99% of the general population exposure (Hattemer-Frey et al., 1990).

Inhalation exposures occurring during the refuelling of automobiles with gasoline can also be important. It has been estimated that a person is exposed to levels of benzene of about 3.2 mg/m3 while

refuelling a vehicle with regular grade gasoline (Bond et al., 1986a), which adds about 10 µg of benzene to the average daily intake. Other sources of inhalation exposure include air near hazardous waste sites or industrial facilities, and emissions from consumer products,

including off-gassing from particle board (ATSDR, 1991). Based on

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extensive studies in the USA, it appears that facilities manufacturing chemicals, drinking-water, food and beverages, and petroleum refining operations play only a minimal role in the total exposure of the general population to benzene (Wallace, 1989b).

Attempts have been made to quantify the level of benzene exposure in the general population (Wallace, 1989a,b; Government of Canada, in press). These studies make various assumptions as to the relative importance and amounts of benzene from various sources, many supported only in unpublished reports. However, they all agree that personal sources (use of products emitting benzene, driving or riding in

automobiles), automobile exhaust and smoking (active and passive) are major sources of benzene to the general population. By far the

greatest source of benzene exposure arises from active smoking (about 1800 µg from about 30 cigarettes/day) (Wallace, 1989b).

In both the USA and Canada, daily intakes from food and water are minimal (up to about 1.4 µg/day). Intake from ambient and indoor air is extremely variable depending upon whether one resides in an

industrial or large urban centre or a more rural environment, but it has been calculated to be about 90 µg/day for a 70-kg adult in Canada and between 180 and 1300 µg for adults in the USA. Other sources are passive smoking (50 µg/day) and automobile-related activities (50 µg/day). For an average non-smoking 70-kg Canadian exposed to passive smoke and various consumer products, the total daily intake of benzene has been calculated to be approximately 230 µg, with an active smoker taking in an additional 1800 µg daily (Government of Canada, in

press). Within the USA, daily intakes for non-smokers have been calculated to range between 430 and 1530 µg/day (Wallace 1989a,b).

The higher levels and wider range of exposures in the USA probably reflect higher levels of benzene detected in the ambient air of large cities and the variations from city to city.

5.3 Occupational exposure during manufacture, formulation or use Occupational exposure occurs mainly during the production, handling and use of benzene and its derivatives. Surveys of occupational exposure have been reported by Fishbein (1984), UBA (1982) and Weaver et al. (1983).

Table 8 presents the number of workers in several industrial sectors exposed to various time-weighted average (TWA) benzene

concentrations. These data are from the USA only and are presented to show the workers at highest risk within an industrialized country.

Without data to the contrary, it should be assumed that the data in Table 8 are, in general, representative of other industrialized

countries. The table does not include workers in firms not covered by the US OSHA regulations, those under other US jurisdictions, those using chemicals containing low levels of benzene, and tank maintenance firms. However, these data do show that in seven major industries in the USA employing 237 812 potentially exposed workers, approximately 95% of the workers were exposed to air levels below 16 mg/m3, i.e.

less than 50% of the 32 mg/m3 TWA. Similarly, most workers in Sweden are exposed to values less than 16 mg/m3, with occasional short-term exposures to 32 mg/m3 being reported among workers in refineries and bulk petrol terminals (Nordlinder & Ramnäs, 1987).

CONCAWE (1986) reported on benzene exposure data measured over recent years in European countries during the manufacture and

distribution of gasoline. These data represent 8-h TWA exposure levels in various sectors of the oil industry. The report concluded that such exposures are normally below 3.2 mg/m3 (1 ppm) for

refinery unit operators, road tanker drivers and service station

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