Environmental Health Criteria 171 DIESEL FUEL AND EXHAUST EMISSIONS

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DIESEL FUEL AND EXHAUST EMISSIONS

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UNITED NATIONS ENVIRONMENT PROGRAMME INTERNATIONAL LABOUR ORGANISATION WORLD HEALTH ORGANIZATION

INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

ENVIRONMENTAL HEALTH CRITERIA 171

DIESEL FUEL AND EXHAUST EMISSIONS

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.

Environmental Health Criteria 171 DIESEL FUEL AND EXHAUST EMISSIONS

First draft prepared by the staff members of the Fraunhofer Institute of Toxicology and Aerosol Research, Germany, under the coordination of Dr. G. Rosner

Published under the joint sponsorship of the United Nations

Environment Programme, the International Labour Organisation, and the World Health Organization, and produced within the framework if the Inter-Organization Programme for the Sound Management of Chemicals.

World Health Organization Geneva, 1996

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

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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 Diesel Fuel and exhaust emission

(Environmental health criteria ; 171)

1.Air pollutants, Enviromental 2.Air pollution 3.Fueloils I.International Programme on Chemical Safety II.Series

ISBN 92 4 157171 3 (NLM Classification: WA 754) 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 1996

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

NOTE TO READERS OF THE CRITERIA MONOGRAPHS PREAMBLE

ENVIRONMENTAL HEALTH CRITERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS WHO DRAFTING GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS

WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS

PART A: DIESEL FUEL A1. SUMMARY

A1.1 Identity, physical and chemical properties, and analytical methods

A1.2 Sources of human and environmental exposure A1.3 Environmental transport, distribution, and transformation

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A1.4 Environmental levels and human exposure

A1.5 Effects on laboratory mammals and in vitro test systems

A1.6 Effects on humans

A1.7 Effects on other organisms in the laboratory and the field

A1.8 Evaluation of human health risks

A1.9 Evaluation of effects on the environment

A2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND ANALYTICAL METHODS

A2.1 Identity

A2.1.1 Fuel components A2.1.1.1 Alkanes A2.1.1.2 Alkenes

A2.1.1.3 Aromatic compounds A2.1.1.4 Sulfur

A2.1.2 Fuel additives

A2.1.2.1 Cetane number improvers A2.1.2.2 Smoke suppressors

A2.1.2.3 Flow improvers

A2.1.2.4 Cloud-point depressors A2.1.2.5 Wax anti-settling additives A2.1.2.6 Other additives

A2.1.3 Quality aspects of diesel fuels

A2.1.3.1 Ignition performance and cetane number

A2.1.3.2 Density

A2.1.3.3 Sulfur content A2.1.3.4 Viscosity

A2.1.3.5 Cold-flow properties A2.2 Physical and chemical properties

A2.3 Analytical methods A2.4 Conversion factors

A3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE A3.1 Natural occurrence

A3.2 Anthropogenic sources

A3.2.1 Production and use

A3.2.1.1 Production process A3.2.1.2 Use

A3.2.1.3 Production and consumption levels

A3.2.2 Emissions during production and use A3.2.2.1 Air

A3.2.2.2 Water A3.2.2.3 Soil

A3.2.3 Accidental releases to the environment A4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION A4.1 Transport and distribution between media

A4.1.1 Evaporation from and dissolution in the aqueous phase

A4.1.2 Transport in and adsorption onto soil and sediment

A4.1.2.1 Soil A4.1.2.2 Sediment A4.2 Transformation and removal A4.2.1 Photooxidation A4.2.2 Biodegradation

A4.2.2.1 Microbial degradation

A4.2.2.2 Phytoplankton and marine algae A4.2.2.3 Invertebrates and vertebrates A4.2.3 Bioaccumulation

A4.2.4 Tainting

A4.2.5 Entry into the food chain

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A4.3 Ultimate fate after use

A4.3.1 Use in motor vehicles A4.3.2 Spills

A4.3.3 Disposal

A5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE A5.1 Environmental levels

A5.2 Exposure of the general population

A5.3 Occupational exposure during manufacture, formulation, or use

A6. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS A7. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS A7.1 Single exposure

A7.2 Short-term exposure

A7.2.1 Subacute exposure

A7.2.1.1 Dermal exposure A7.2.1.2 Inhalation A7.2.2 Subchronic exposure

A7.2.2.1 Dermal exposure A7.2.2.2 Inhalation A7.3 Long-term exposure

A7.3.1 Dermal exposure A7.3.2 Inhalation

A7.4 Dermal and ocular irritation; dermal sensitization A7.4.1 Dermal irritation

A7.4.2 Ocular irritation A7.4.3 Sensitization

A7.5 Reproductive toxicity, embryotoxicity, and teratogenicity

A7.6 Mutagenicity and related end-points A7.6.1 In vitro

A7.6.2 In vivo A7.7 Carcinogenicity

A7.7.1 Dermal exposure A7.7.2 Inhalation A8. EFFECTS ON HUMANS

A8.1 Exposure of the general population A8.2 Occupational exposure

A9. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD A9.1 Laboratory experiments

A9.1.1 Microorganisms A9.1.1.1 Water A9.1.1.2 Soil A9.1.2 Aquatic organisms

A9.1.2.1 Plants (phytoplankton) A9.1.2.2 Invertebrates

A9.1.3 Terrestrial organisms A9.1.3.1 Plants

A9.1.3.2 Invertebrates A9.1.3.3 Vertebrates A9.2 Field observations

A9.2.1 Microorganisms.

A9.2.1.1 Water A9.2.1.2 Soil A9.2.2 Aquatic organism A9.2.3 Terrestrial organisms A9.2.3.1 Plants

A9.2.3.2 Invertebrates A9.2.3.3 Vertebrates

A10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT

A10.1.1 Exposure of the general population

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A10.1.2 Occupational exposure A10.1.3 Non-neoplastic effects A10.1.4 Neoplastic effects

A10.2 Evaluation of effects on the environment A11. RECOMMENDATIONS

A11.1 Recommendations for the protection of human health A11.2 Recommendation for the protection of the environment A11.3 Recommendations for further research

A12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES PART B: DIESEL EXHAUST EMISSIONS

B1. SUMMARY

B1.1 Identity, physical and chemical properties, and analytical methods

B1.2 Sources of human and environmental exposure B1.3 Environmental transport, distribution, and transformation

B1.4 Environmental levels and human exposure

B1.5 Kinetics and metabolism in laboratory animals and humans

B1.5.1 Deposition

B1.5.2 Retention and clearance of particles B1.5.3 Retention and clearance of polycyclic aromatic hydrocarbons adsorbed onto diesel soot

B1.5.4 Metabolism

B1.6 Effects on laboratory mammals and in vitro test systems

B1.7 Effects on humans

B1.8 Effects on other organisms in the laboratory and the field

B1.9 Evaluation of human health risks B1.9.1 Non-neoplastic effects B1.9.2 Neoplastic effects

B1.10 Evaluation of effects on the environment B2. IDENTITY AND ANALYTICAL METHODS

B2.1 Identity

B2.1.1 Chemical composition of diesel exhaust gases

B2.1.2 Type and composition of emitted particulate matter

B2.2 Analytical methods B2.2.1 Sampling

B2.2.1.1 Sampling from undiluted exhaust gas (raw gas sampling)

B2.2.1.2 Sampling from diluted exhaust (dilution tube sampling) B2.2.2 Extraction from particles

B2.2.3 Clean-up and fractionation B2.2.4 Chemical analysis

B2.3 Conversion factors

B3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE B3.1 Anthropogenic sources

B3.1.1 Diesel exhaust emissions

B3.1.1.1 Emission of chemical

constituents with the gaseous portion of diesel exhaust B3.1.1.2 Emission of particulate matter and adsorbed components in diesel exhaust gases

B3.1.2 Parameters that influence diesel exhaust emissions

B3.1.2.1 Engine conditions

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B3.1.2.2 Fuel specification B3.1.2.3 Malfunction

B3.1.3 Total emissions by diesel engines B3.1.4 Control of emissions

B3.1.4.1 Particle traps

B3.1.4.2 Catalytic converters B3.2 Regulatory approaches

B4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION B4.1 Transport and distribution between media

B4.2 Transformation and removal

B5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE B5.1 Exposure of the general population B5.2 Occupational exposure

B5.2.1 Truck drivers and mechanics B5.2.2 Bus garage and other bus workers B5.2.3 Fork-lift truck operators

B5.2.4 Railroad workers B5.2.5 Mine workers B5.2.6 Fire fighters B5.3 Biomonitoring

B5.3.1 Urinary mutagenicity B5.3.2 Other analyses

B6. KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS B6.1 Deposition

B6.2 Retention and clearance of particles

B6.3 Retention and clearance of polycyclic aromatic hydrocarbons adsorbed onto diesel soot

B6.4 Metabolism

B7. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS B7.1 Single exposure

B7.2 Short-term exposure

B7.3 Long-term exposure and studies of carcinogenicity B7.3.1 Non-neoplastic effects

B7.3.2 Carcinogenicity

B7.3.2.1 Inhalation

B7.3.2.2 Other routes of exposure

B7.4 Dermal and ocular irritation; dermal sensitization B7.5 Reproductive toxicity, embryotoxicity, and

teratogenicity

B7.5.1 Reproductive toxicity B7.5.2 Embryotoxicity

B7.5.3 Teratogenicity

B7.6 Mutagenicity and related end-points B7.6.1 In vitro

B7.6.2 In vivo

B7.6.3 DNA adduct formation B7.7 Special studies

B7.7.1 Immunotoxicity B7.7.2 Behavioural effects

B7.8 Factors that modify toxicity; toxicity of metabolites

B7.9 Mechanisms of toxicity; mode of action B7.9.1 Carcinogenic effects

B7.9.1.1 DNA-reactive mechanisms

B7.9.1.2 Cytotoxicity with regenerative cell proliferation

B7.9.1.3 Effects of particles

B7.9.1.4 Effects of polycyclic aromatic hydrocarbons

B7.9.2 Noncarcinogenic effects B8. EFFECTS ON HUMANS

B8.1 General population

B8.1.1 Acute exposure: olfactory, nasal, and

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ocular irritation B8.1.2 Air pollution B8.2 Occupational exposure

B8.2.1 Effects on the respiratory system B8.2.1.1 Symptoms

B8.2.1.2 Acute changes in pulmonary function

B8.2.1.3 Pulmonary effects

B8.2.2 Epidemiological studies (noncarcinogenic effects)

B8.2.2.1 Effects on the respiratory system

B8.2.2.2 Effects on the circulatory system

B8.2.3 Epidemiological studies (carcinogenic effects)

B8.2.3.1 Lung cancer

B8.2.3.2 Urinary bladder cancer

B9. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD B10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE

ENVIRONMENT

B10.1 Exposure of the general population B10.2 Occupational exposure

B10.3 Non-neoplastic effects

B10.3.1 Hazard identification B10.3.1.1 Humans

B10.3.1.1 Experimental animals B10.3.2 Dose-response assessment

B10.3.2.1 Epidemiological studies

B10.3.2.2 Studies in experimental animals B10.3.3 Exposure assessment

B10.3.4 Risk characterization B10.3.4.1 Humans

B10.3.4.2 Experimental animals B10.4 Neoplastic effects

B10.4.1 Hazard identification

B10.4.1.1 Lung cancer: occupational exposure

B10.4.1.2 Urinary bladder cancer:

occupational exposure B10.4.2 Dose-response assessment

B10.4.2.1 Lung cancer

B10.4.2.2 Urinary bladder cancer B10.4.3 Exposure assessment

B10.4.4 Risk characterization

B10.4.4.1 Human lung cancer

B10.4.4.2 Human urinary bladder cancer B10.4.4.3 Risk characterization based on studies in experimental animals Appendix B10.1 Construction of a biologically based (alternative) model Appendix B10.2 E-M algorithm

Appendix B10.3 A tumour growth model B11. RECOMMENDATIONS

B11.1 Recommendations for the protection of human health B11.2 Recommendation for the protection of the environment B11.3 Recommendations for further research

B12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES REFERENCES

RESUMÉ

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RESUMEN

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 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. 979 9111).

* * *

This publication was made possible by grant number 5 U01 ES02617-15 from the National Institute of Environmental Health

Sciences, National Institutes of Health, USA, and by financial support from the European Commission.

Environmental Health Criteria PREAMBLE

Objectives

The WHO Environmental Health Criteria Programme was initiated in 1973, with the following objectives:

(i) to assess information on the relationship between exposure to environmental pollutants and human health and to provide guidelines for setting exposure limits;

(ii) to identify new or potential pollutants;

(iii) to identify gaps in knowledge concerning the health effects of pollutants;

(iv) to promote the harmonization of toxicological and

epidemiological methods in order to have internationally comparable results.

The first Environmental Health Criteria (EHC) monograph, on mercury, was published in 1976; numerous assessments of chemicals and of physical effects have since been produced. Many EHC monographs have been devoted to toxicological methods, e.g. for genetic, neurotoxic, teratogenic, and nephrotoxic effects. Other publications have been concerned with e.g. epidemiological guidelines, evaluation of short-term tests for carcinogens, biomarkers, and effects on the elderly.

Since the time of its inauguration, the EHC Programme has widened its scope, and the importance of environmental effects has been

increasingly emphasized in the total evaluation of chemicals, in addition to their health effects.

The original impetus for the Programme came from resolutions of

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the World Health Assembly and the recommendations of the 1972 United Nations Conference on the Human Environment. Subsequently, the work became an integral part of the International Programme on Chemical Safety (IPCS), a cooperative programme of UNEP, ILO, and WHO. In this manner, with the strong support of the new partners, the importance of occupational health and environmental effects was fully recognized.

The EHC monographs have become widely established, used, and recognized throughout the world.

The recommendations of the 1992 United Nations Conference on Environment and Development and the subsequent establishment of the Intergovernmental Forum on Chemical Safety, with priorities for action in the six programme areas of Chapter 19, Agenda 21, lend further weight to the need for EHC assessments of the risks of chemicals.

Scope

The Criteria monographs are intended to provide critical reviews of the effect on human health and the environment of chemicals,

combinations of chemicals, and physical and biological agents. They include reviews of studies that are of direct relevance for the

evaluation and do not describe every study that has been carried out.

Data obtained worldwide are used, and results are quoted from original studies, not from abstracts or reviews. Both published and unpublished reports are considered, and the authors are responsible for assessing all of the articles cited; however, preference is always given to published data, and unpublished data are used only when relevant published data are absent or when the unpublished data are pivotal to the risk assessment. A detailed policy statement is available that describes the procedures used for citing unpublished proprietary data, so that this information can be used in the evaluation without

compromising its confidential nature (WHO, 1990).

In the evaluation of human health risks, sound data on humans, whenever available, are preferred to data on experimental animals.

Studies of animals and in vitro systems provide support and are used mainly to supply evidence missing from human studies. It is mandatory that research on human subjects be conducted in full accord with ethical principles, including the provisions of the Helsinki Declaration.

The EHC monographs are intended to assist national and

international authorities in making risk assessments and subsequent risk management decisions. They represent a thorough evaluation of risks and are not in any sense recommendations for regulation or setting standards. The latter are the exclusive purview of national and regional governments.

Content

The layout of EHC monographs for chemicals is outlined below.

* Summary: a review of the salient facts and the risk evaluation of the chemical

* Identity: physical and chemical properties, analytical methods * Sources of exposure

* Environmental transport, distribution, and transformation * Environmental levels and human exposure

* Kinetics and metabolism in laboratory animals and humans * Effects on laboratory mammals and in-vitro test systems * Effects on humans

* Effects on other organisms in the laboratory and the field * Evaluation of human health risks and effects on the environment * Conclusions and recommendations for protection of human health

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and the environment * Further research

* Previous evaluations by international bodies, e.g. the

International Agency for Research on Cancer, the Joint FAO/WHO Expert Committee on Food Additives, and the Joint FAO/WHO Meeting on Pesticide Residues

Selection of chemicals

Since the inception of the EHC Programme, the IPCS has organized meetings of scientists to establish lists of chemicals that are of priority for subsequent evaluation. Such meetings have been held in Ispra, Italy (1980); Oxford, United Kingdom (1984); Berlin, Germany (1987); and North Carolina, United States of America (1995). The selection of chemicals is based on the following criteria: the

existence of scientific evidence that the substance presents a hazard to human health and/or the environment; the existence of evidence that the possible use, persistence, accumulation, or degradation of the substance involves significant human or environmental exposure; the existence of evidence that the populations at risk (both human and other species) and the risks for the environment are of a significant size and nature; there is international concern, i.e. the substance is of major interest to several countries; adequate data are available on the hazards.

If it is proposed to write an EHC monograph on a chemical that is not on the list of priorities, the IPCS Secretariat first consults with the cooperating organizations and the participating institutions.

Procedures

The order of procedures that result in the publication of an EHC monograph is shown in the following flow chart. A designated staff member of IPCS, responsible for the scientific quality of the document, serves as Responsible Officer (RO). The IPCS Editor is responsible for the layout and language. The first draft, prepared by consultants or, more usually, staff at an IPCS participating

institution is based initially on data provided from the International Register of Potentially Toxic Chemicals and reference data bases such as Medline and Toxline.

The draft document, when received by the RO, may require an

initial review by a small panel of experts to determine its scientific quality and objectivity. Once the RO finds the first draft acceptable, it is distributed in its unedited form to over 150 EHC contact points throughout the world for comment on its completeness and accuracy and, where necessary, to provide additional material. The contact points, usually designated by governments, may be participating institutions, IPCS focal points, or individual scientists known for their particular expertise. Generally, about four months are allowed before the

comments are considered by the RO and author(s). A second draft incorporating the comments received and approved by the Director, IPCS, is then distributed to Task Group members, who carry out a peer review at least six weeks before their meeting.

The Task Group members serve as individual scientists, not as representatives of any organization, government, or industry. Their function is to evaluate the accuracy, significance, and relevance of the information in the document and to assess the risks to health and the environment from exposure to the chemical. A summary and

recommendations for further research and improved safety are also drawn up. The composition of the Task Group is dictated by the range

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of expertise required for the subject of the meeting and by the need for a balanced geographical distribution.

The three cooperating organizations of the IPCS recognize the important role played by nongovernmental organizations, so that

representatives from relevant national and international associations may be invited to join the Task Group as observers. While observers may provide valuable contributions to the process, they can speak only at the invitation of the Chairperson. Observers do not participate in the final evaluation of the chemical, which is the sole responsibility of the Task Group members. The Task Group may meet in camera when it considers that to be appropriate.

All individuals who participate in the preparation of an EHC monograph as authors, consultants, or advisers must, in addition to serving in their personal capacity as scientists, inform the RO if at any time a conflict of interest, whether actual or potential, could be perceived in their work. They are required to sign a statement to that effect. This procedure ensures the transparency and probity of the process.

When the Task Group has completed its review and the RO is satisfied as to the scientific correctness and completeness of the document, it is edited for language, the references are checked, and camera-ready copy is prepared. After approval by the Director, IPCS, the monograph is submitted to the WHO Office of Publications for printing. At this time, a copy of the final draft is also sent to the Chairperson and Rapporteur of the Task Group to check for any errors.

It is accepted that the following criteria should initiate the updating of an EHC monograph: new data are available that would substantially change the evaluation; there is public concern about health or environmental effects of the agent because of greater exposure; an appreciable time has elapsed since the last evaluation.

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All participating institutions are informed, through the EHC progress report, of the authors and institutions proposed for the drafting exhaust emissions of the documents. A comprehensive file of all comments received on drafts of each EHC monograph is maintained and is available on request. The chairpersons of task groups are briefed before each meeting on their role and responsibility in ensuring that these rules are followed.

WHO DRAFTING GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS

WHO, Geneva, 6-9 December 1993 Members

Dr J.A. Bond, Chemical Industry Institute of Toxicology, Research Triangle Park, NC, United State

Dr R.P. Bos, University of Nijmegen, Nijmegen, Netherlands

Dr R. Brown, Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom (Joint Rapporteur)

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Dr Chao Chen, Human Health Assessment Group, United States Environmental Protection Agency, Washington DC, United States Dr I. Farkas, National Institute of Hygiene, Budapest, Hungary Dr E. Garshick, Pulmonary Section, Brockton/West Roxbury VA Medical Center, West Roxbury, MA, United States

Dr P. Gustavsson, North Western Health Board, Stockholm, Sweden Dr D. Guth, United States Environmental Protection Agency, Research Triangle Park, NC, United States

Dr U. Heinrich, Department of Experimental Hygiene, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany

Dr R.F. Hertel, Federal Health Office, Bundesgesundheitsamt, Berlin, Germany

Professor G. Oberdörster, Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, United States Dr W. Pepelko, United States Environmental Protection Agency,

Washington DC, United States

Dr P.J.A. Rombout, Laboratory of Toxicology, National Institute of Public Health and Environmental Protection, Bilthoven, Netherlands

(Vice-Chairman)

Dr G. Rosner, Hazardous Substances Documentation Group, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany

Dr J. Roycroft, National Institute of Environmental Health Sciences, Research Triangle Park, NC, United States

Dr A. Sivak, Environmental Health Sciences, Saint Augustine, FL, United States (Chairman)

Dr B.H. Thomas, Environmental Health Directorate, Ottawa, Canada Dr L. Turrio, Istituto Superiore di Sanita, Laboratorio Tossicologia Comparata e Ecotossicologia, Rome, Italy

Mr. R. Waller, Department of Health, London, United Kingdom Secretariat

Dr P. Boffetta, International Agency for Research on Cancer, Lyon, France (6-7 December 1993)

Dr E. Smith, International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland

Representatives/Observers CONCAWE

Dr R.H. McKee, Exxon Biomedical Sciences, East Millstone, NJ, United States

UNITED KINGDOM DEPARTMENT OF THE ENVIRONMENT

Dr P.T.C. Harrison, MRC Institute of Environment & Health, Leicester, United Kingdom

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WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS

Fraunhofer Institute of Toxicology & Aerosol Research, Hanover 27 June-1 July 1994

Members

Dr J.A. Bond, Chemical Industry Institute of Toxicology, Research Triangle Park, NC, United States

Dr R. Brown, Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom

Dr Chao Chen, Human Health Assessment Group, United States Environmental Protection Agency, Washington DC, United States

Dr E. Garshick, Pulmonary Section, Brockton/West Roxbury VA Medical Center, West Roxbury, MA, United States

Dr U. Heinrich, Department of Experimental Hygiene, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany

Dr R.F. Hertel, Federal Health Office, Bundesgesundheitsamt, Berlin, Germany

Dr Jun Kagawa, Tokyo Women's Medical College, Tokyo, Japan Professor G. Oberdörster, Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, United States Dr P.J.A. Rombout, Laboratory of Toxicology, National Institute of Public Health and Environmental Protection, Bilthoven, Netherlands Dr M. Roller, Medizinishes Institut für Umwelthyglene an der

Universität Düsseldorf, Düsseldorf, Germany Dr G. Rosner, Hazardous Substances Documentation Group, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany

Dr A. Sivak, Environmental Health Sciences, Saint Augustine, FL, United States

Dr L. Turrio, Istituto Superiore di Sanita, Laboratorio Tossicologia Comparata e Ecotossicologia, Rome, Italy

Mr R. Waller, Department of Health, London, United Kingdom Secretariat

Dr H. Moller, International Agency for Research on Cancer, Lyon, France

Dr E. Smith, International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland

Dr M. Younes, European Centre for Environment and Health, Bilthoven, Netherlands

Representatives/Observers

Dr Lutz Von Meyerinck, BP Oil Europe, Brussels, Belgium GERMAN AUTOMOBILE ASSOCIATION

Dr N. Pelz, Mercedes-Benz AG, Stuttgart, Germany

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ILSI

Dr I.T. Salmeen, Chemistry Department, Ford Motor Company, Dearborn, MI, United States

IUTOX

Dr P. Montuschi, Department of Pharmacology, School of Medicine, Catholic University of the Sacred Heart, Rome, Italy

ENVIRONMENTAL HEALTH CRIETERIA FOR DIESEL FUEL AND EXHAUST EMISSIONS A WHO Task Group on Environmental Health Criteria for Diesel Fuel and Exhaust Emissions met at the Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany from 27 June to 1 July 1994.

Dr G. Rosner, Fraunhofer Institute, welcomed the participants on behalf of the Institute and its Director, Professor U. Mohr, and Dr E.M. Smith, IPCS, welcomed the participants on behalf of

Dr M. Mercier, Director of the IPCS, and on behalf of the heads of the three IPCS cooperating organizations (UNEP, ILO, and WHO). The Task Group reviewed and revised the draft and evaluated the risks for human health and the environment from exposure to diesel fuel and exhaust emissions.

The first draft of the monograph was prepared at the Fraunhofer Institute. After international circulation for comment, this draft was extensively revised by a Working/Drafting Group, convened at WHO, Geneva, from 6 to 9 December 1993, and a second draft was prepared for further international circulation for comment. The membership of the drafting group is shown previously. A final draft, incorporating comments received from the IPCS contact points for Environmental Health Criteria monographs and new material, was completed at the Fraunhofer Institute under the coordination of Dr G. Rosner, with important contributions to the text from the following Institute staff members:

Dr B. Bellman Dr A. Boehnke Dr O. Creutzenberg Dr J. Kielhorn

Dr E.M. Smith of the IPCS Central Unit was responsible for the scientific content of the monograph and Mrs E. Heseltine, Lajarthe, France, for the editing.

The efforts of all who helped in the preparation and finalization of the monograph are gratefully acknowledged.

PART A DIESEL FUEL A1. SUMMARY

A1.1 Identity, physical and chemical properties, and analytical methods

Diesel fuel is a complex mixture of normal, branched, and cyclic alkanes (60 to > 90% by volume; hydrocarbon chain length, usually between C9 and C30); aromatic compounds, especially alkylbenzenes (5-40% by volume); and small amounts of alkenes (0-10% by volume) obtained from the middle-distillate, gas-oil fraction during petroleum separation. Benzene, toluene, ethylbenzene, and xylenes and polycyclic aromatic hydrocarbons (PAHs), especially naphthalene and its

methyl-substituted derivatives, may be present at levels of parts per million in diesel fuel. The sulfur content of diesel fuels depends on the source of crude oil and the refinery process. It is regulated by

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law in a number of countries and is usually between 0.05 and 0.5

weight percent. Additives are used to influence the flow, storage, and combustion of diesel fuel, to differentiate products, and to meet trademark specifications. At room temperature, diesel fuels are generally moderately volatile, slightly viscous, flammable, brown liquids with a kerosene-like odour. The boiling ranges are usually between 140 and 385°C (> 588°C for marine diesel fuel); at 20°C, the density is 0.87-1.0 g/cm³ and the water solubility is

0.2-5 mg/litre. The quality and composition of diesel fuel influence the emissions of pollutants from diesel engines considerably.

Important variables are ignition behaviour (expressed in terms of cetane number), density, viscosity, and sulfur content. The

specifications of commercial diesel fuel differ considerably in different countries.

Heating fuels and some kerosene jet fuels produced during the refining process may have a composition similar to that of diesel fuel, although with different additives. Biological data on these mixtures have therefore also been taken into account in the

assessments of toxicity and ecotoxicity.

Owing to the complexity of the diesel fuel mixture, there is no specific analytical method, and the analytical techniques used in most environmental assessments are suitable only for measuring the total petroleum hydrocarbon mixture. The methods consist of preliminary solvent extraction, a clean-up procedure to remove naturally occurring hydrocarbons, and subsequent detection by gravimetry, infrared

spectroscopy or gas chromatography. Neither the gravimetric nor the infrared technique provides useful qualitative or quantitative

information on contaminants and can thus be used only for screening.

Gas chromatography combined with detection techniques such as flame ionization and mass spectrometry is the standard procedure for

analysing environmental samples. Many other methods are available for the analysis of individual hydrocarbons in diesel fuels.

A1.2 Sources of human and environmental exposure

Diesel fuels are produced by refining crude oils. In order to meet technical specifications for performance, diesel fuels are generally blended; further formulation with additives improves their properties for specific uses. Diesel fuels are widely used as

transportation fuels. The more volatile fuels, with low viscosity, are required for high-speed engines and the heavier grades for railroad and ship diesel engines. Much heavy-duty road transport is powered by diesel engines. Passenger cars powered by diesel engines are becoming increasingly more common in Europe and Japan (10-25%), whereas in North America the percentage of diesel-fuelled passenger cars is about 1-2%, with a slightly decreasing tendency. Diesel fuel is used in stationary engines and in boilers, e.g. reciprocating engines, gas turbines, pipeline pumps, gas compressors, steam processing units in electric power plants, burner installations, and industrial space and water heating facilities.

Over the last five years, the worldwide demand for diesel fuels has increased steadily. In 1985, the following amounts of diesel fuel were consumed: about 170 000 kt per year in North America; about 160 000 kt per year, including gas oils, in the European Union; and about 46 000 kt per year in Australia, Japan, and New Zealand, equivalent to a total of 1062 kt per day. In 1990, world demand was reported to be about 1110 kt per day.

No information is available on emissions during the production of diesel fuels; however, this source would seem to be of minor

importance, because the refining process is carried out in closed

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systems. Emissions may occur principally during storage and

transportation. Diesel fuels are released as a result of spills and at filling stations during the refuelling of vehicles. The atmosphere and the hydrosphere are the most heavily affected environmental

compartments. Soil contamination with diesel fuels may occur during accidents and is also a problem in railroad yards. The numerous techniques for cleaning soils contaminated with diesel fuel include excavation, biological methods, and containment.

A1.3 Environmental transport, distribution, and transformation Very few data are avilable on the environmental fate of diesel fuels, but the mechanisms of their distribution and transformation are considered to be comparable to those of heating fuels, such as No. 2 fuel oil, which have been well studied. Spills of diesel fuel on water spread almost immediately to form a 'slick'. The polar and

low-relative-molecular-mass components dissolve and leach out of the slick, and the volatile components evaporate from the surface;

microbial degradation also begins. Chemical and biological weathering alter the composition of the spill. These processes are dependent on temperature; spills that occur in Arctic conditions are more

persistent than those that occur in temperate climates. In marine environments, most of the low-relative-molecular-mass aromatic species are dissolved into the water phase, but the primary branched alkanes, cycloalkanes, and remaining aromatic compounds may remain in sediments for more than a year.

Although no information is available on the photooxidation of diesel fuels in water and air, evaporated oil components are degraded photochemically. No. 2 fuel oil has been shown to be photooxidized rapidly in water under environmental conditions.

The individual constituents of diesel fuel are inherently biodegradable, to varying degrees and at different rates. The

n-alkane, n-alkylaromatic, and simple aromatic molecules in the C₁₀-C22

range are the most readily degradable. Smaller molecules are generally rapidly metabolized. Long-chain n-alkanes are more slowly degraded, owing to their hydrophobicity and because they are viscous or solid at ambient temperatures. Branched alkanes and cycloalkanes are relatively resistant to biological breakdown, and PAHs are resistant. The overall rates of degradation of hydrocarbons are limited by temperature, water content, oxygen, pH, inorganic nutrients, and microbial metabolic versatility.

Unicellular algae can take up and metabolize both aliphatic and aromatic hydrocarbons, but the extent to which this actually occurs in nature is poorly understood. Unlike microorganisms that use petroleum carbons as a carbon source, animals generally oxidize and conjugate products, rendering end-products that are more soluble and therefore easier to excrete. All animal species tested can take up petroleum hydrocarbons. PAHs, crude oil, and refined petroleum products are known to induce cytochrome P450 enzymes and to increase the levels of hydrocarbon metabolism in numerous marine and freshwater fish species.

Few data are available on the bioaccumulation of diesel fuel in the laboratory, but there is plentiful evidence from studies of spills and laboratory studies on other oils, particularly No. 2 fuel oil, that aquatic organisms bioconcentrate hydrocarbons. The

n-octanol-water partition coefficient for diesel fuel is 3.3-7.06, which suggests high potential bioaccumulation; however, many of the lower-relative-molecular-mass compounds are readily metabolized, and the actual bioaccumulation of higher-relative-molecular-mass compounds is limited by their low water solubility and large molecular size.

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Thus, actual bioaccumulation may be low.

Fish have been tainted by diesel fuel after spills. No data are available on the biomagnification of diesel fuel.

No experimental data are available on the movement of diesel fuel through the soil, although a direct correlation between the movement and kinematic viscosity has been proposed. The movement of kerosene through soil depends on the moisture content and nature of the soil.

A1.4 Environmental levels and human exposure

As diesel fuels are complex mixtures, the environmental levels have not been measured. The individual constituents of diesel fuels can be detected in almost all compartments of the environment,

although their source cannot be verified. The general population may be exposed to diesel fuel at filling stations and as a result of spills.

Occupational exposure to diesel fuel occurs in a large number of activities. Because of their low volatility, diesel fuels should generate only low concentrations of vapours at normal temperatures, but high operating temperatures can result in significant

concentrations.

A1.5 Effects on laboratory mammals and in-vitro test systems

The acute toxicity of diesel fuels is low after oral or dermal exposure or after inhalation. The oral LD50 value was > 5000 mg/kg body weight in all species tested (mouse, rabbit, rat, guinea-pig).

Dermal application resulted in an LD₅₀ value of > 5000 mg/kg body weight in mice and rabbits, although values of > 2000 mg/kg body weight were reported for some kerosenes and middle distillates, with different protocols and lower limit doses. The LC0 value in rats exposed by inhalation was about 5 mg/litre, except for one

straight-run middle distillate for which a value of 1.8 mg/litre was seen.

In rabbits treated dermally with up to 8000 µl/kg body weight per day and mice with up to 40 000 mg/kg body weight per day, acanthosis and hyperkeratosis due to severe irritation were seen. Rabbits were more sensitive than mice. Inhalation of diesel fuel was neurodepressive in mice at concentrations up to 0.2 mg/litre but not in rats exposed to up to 6 mg/litre. Body and liver weights were reduced in rats.

Mice, rats, and dogs did not show significant cumulative toxicity after inhalation of up to 1.5 mg/litre subchronically. The specific nephropathy syndrome seen in male rats is linked to an inherent accumulation of hyalin droplets in the renal tubules.

The only effects of long-term exposures were ulceration after dermal application to mice (250 or 500 mg/kg body weight per day) and significant alterations in organ weight after inhalation of 1 or 5 mg/litre by rats. In both studies the mean body weights were reduced.

Various types of diesel fuels were slightly to severely

irritating to the skin of rabbits. Diesel fuels do not irritate the eye, but some kerosenes have been reported to have a slight irritating effect. Diesel fuels do not cause skin sensitization.

Diesel and jet fuels (kerosene) were neither embryotoxic nor teratogenic in two studies in rats exposed by inhalation to 100 or

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400 ppm and in one study in which rats were given up to 2000 mg/kg body weight per day by gavage. In the last study, reduced fetal weight was observed.

Tests in Salmonella typhimurium did not provide clear evidence of mutagenicity. Some positive findings in S. typhimurium and in mouse lymphoma cells were considered to be equivocal owing to the inconsistency of the results. Tests for genotoxicity in mice in vivo (induction of micronuclei or chromosomal aberrations) also gave equivocal or negative responses.

Diesel fuels induced a low level of dermal carcinogenicity. In the present state of research, it cannot be concluded whether the carcinogenic potency of diesel fuels is mediated by a genotoxic mechanism or by chronic dermal damage.

A1.6 Effects on humans

Non-occupational exposure to diesel fuel can occur during manual filling of fuel tanks. The primary source of dermal exposure is

accidental spills, which result in immediate high levels of exposure but are of short duration.

After accidental dermal contact, anuria, renal failure, gastro- intestinal symptoms, and cutaneous hyperkeratosis have been reported.

Toxic lung disease has been observed after accidental ingestion of diesel fuel and subsequent aspiration. Persistent productive cough has been reported after inhalation. In a case-control study of men exposed to diesel fuel, an increased risk for cancer of the lung other than adenocarcinoma was found; a positive association was also seen with prostatic cancer, although a higher risk was noted for the group with 'nonsubstantial' exposure than for that with 'substantial' exposure.

In a cross-sectional study of factory workers exposed to kerosene jet fuels, dizziness, headache, nausea, palpitation, pressure in the chest, and eye irritation were found to be more prevalent than in unexposed controls. The time-weighted average concentration of vapour from the fuel in the breathing zone was estimated to be 128-423 mg/m³.

A1.7 Effects on other organisms in the laboratory and the field

Diesel fuel is more toxic than crude oil to aquatic organisms and plants. The ecotoxicity of diesel fuel is generally attributed to soluble aromatic compounds, but insoluble aliphatic hydrocarbons may also be implicated. Of the aromatic compounds, monoaromatics are the least toxic, their acute toxicity increasing with molecular mass up to the four- to five-ring compounds, although these are poorly soluble in seawater. In some animals, e.g. fish and birds, physical coating of the body surface by the fuel can produce toxicity and mortality.

Laboratory experiments have been carried out on diesel fuel, water-soluble fractions, oil-water dispersions, and microencapsulated oil. Diesel fuel did not significantly reduce the growth in culture of the green alga Euglena gracilis, whereas a low concentration (0.1%) almost completely inhibited the growth of Scenedesmus quadricauda.

Light diesel fuel (0.05%) stimulated the growth, photosynthesis, and chlorophyll asynthesis of Chlorella salina but slightly inhibited respiration; at higher concentrations, the growth rate and

photosynthesis were greatly reduced. Long-term exposure inhibited the growth of the benthic algae Ascophyllum nodosum and Laminaria

digitata. In blue-green algae, photosynthesis was reduced by the aromatic and asphaltic fractions but not by the aliphatic fraction.

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Diesel fuel was acutely toxic to Daphnia spp., chironomid larvae, and the mollusc Viviparus bengalensis (Gastropoda). A

concentration of 0.1 ml/litre caused the death of tidepool copepods, Tigriopus californicus, within five days.

Mytilus edulismussels accumulate diesel fuel, have markedly reduced feeding and growth rates, and show reproductive toxicity after chronic exposure to diesel fuel. The EC50 for spawning in mussels

exposed for 30 days was about 800 µg/litre. The LC50 of microencapsulated diesel oil after exposure of maturing mussels for

30 days was about 5000 µg/litre. Diesel oil was more toxic to larvae than to juveniles: 10 µg/litre had adverse effects on the growth of larvae.

Freshwater crabs (Barytelphusa cunicularis) exposed to sublethal concentrations of diesel fuel for up to 96 h generally reduced their oxygen consumption, particularly at lower exposures up to 8 h. With longer exposures, the oxygen consumption was equal to or higher than that of the controls.

In 96-h tests of acute toxicity in juvenile salmonids under static conditions, diesel fuel was more toxic to pink salmon,

Onchorhychus gorbuscha (LC₅₀: 32-123 mg/litre), than to cohosalmon, O. kisutch (LC50: 2186-3017 mg/litre), or rainbow trout,

O. mykiss (LC50: 3333-33 216 mg/litre), irrespective of water type.

The threshold for detection of behavioural responses of cod ( Gadus morhua L.) exposed to diesel fuel in seawater was within 100-400 ng/litre. The Antarctic fish Pagothenia borchgrevinki

withstood an undiluted water-soluble fraction of diesel fuel oil for up to 72 h but showed signs of stress.

Birds are affected externally and internally by oil

contamination. Diesel fuel destroys the waterproof nature of the birds' plumage and is ingested during preening. Diesel and fuel oil fed by gavage at 2 ml/kg body weight to ducks caused lipid pneumonia, extreme inflammation of the lungs, fatty infiltration of the liver, and hepatic degeneration after 24 h. Administration of diesel or fuel oil at 1 ml/kg caused severe irritation of the digestive tract and toxic nephrosis. Higher doses resulted in adrenal enlargement (mainly due to hyperplasia of cortical tissue), depression of plasma

cholinesterase levels, ataxia, and tremors. Doses up to 20 ml/kg body weight were not fatal to healthy birds, but the LD50 for diesel and fuel oil administered to birds under stress was 3-4 ml/kg body weight.

After spills of diesel fuel, zooplankton appear to be highly vulnerable to dispersed and dissolved petroleum constituents but less so to floating oils. Aquatic organisms may be affected in a number of ways, including direct mortality (fish eggs, copepods, and mixed plankton), external contamination by oil (chorions of fish eggs and cuticles and feeding appendages of crustaceans), tissue contamination by aromatic constituents, abnormal development of fish embryos, and altered metabolic rates.

The general population can be exposed to diesel fuel and other middle distillates at filling stations, as a result of accidental spills, during the handling of such fuels, and during use of kerosene for domestic cooking or heating. Workers can be exposed to diesel fuel and other middle distillates while handling and discharging the fuel at terminals, storage tanks, and filling stations; during the

manufacture, repair, maintenance, and testing of diesel engines and other equipment; during use of diesel fuel as a cleaning agent or

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solvent; and in handling and routine sampling of diesel fuel in the laboratory. Owing to the low volatility of diesel fuel, only low concentrations of vapour are likely to occur at room temperature, although in confined spaces at high temperatures significant levels may be found.

Exposure to vapour is minimal during the normal handling of diesel fuel. The most likely effect on human health is dermatitis after skin contact. Diesel fuel is a skin irritant but does not appear to irritate the eye. Acute toxic effects on the kidney can occur after dermal exposure, but the effects of long-term dermal absorption of low concentrations are unknown.

Diesel fuels are toxic when ingested, sometimes resulting in regurgitation and aspiration, which can cause chemical pneumonia; the same is true for any hydrocarbon in a particular range of viscosity.

In rodents exposed by inhalation to diesel fuel at concentrations up to 0.2 mg/litre, a neurodepressive effect was seen in mice but not in rats at the higher concentrations. Subchronic exposure by

inhalation to various distillate fuels induced specific

alpha2-microglobulin nephropathy in male rats; this effect is considered irrelevant for humans.

Diesel fuels were neither embryotoxic nor teratogenic in animals exposed orally or by inhalation.

There is no clear evidence of mutagenic activity in bacteria, and the results of other tests for genotoxicity in vitro and in vivo were equivocal.

A case-control study of workers exposed to diesel fuel suggested an increased risk for cancer of the lung other than adenocarcinoma and for prostatic cancer. In neither case was there an exposure-response relationship. In view of the small number of studies available, the small number of cases, and the correspondingly wide confidence intervals, no conclusion can be drawn about the carcinogenicity to humans of diesel fuel.

In mice, dermally administered diesel fuels had weak carcinogenic potential. In view of the absence of clear genotoxicity, cancer could be induced by nongenotoxic mechanisms, e.g. by chronic dermal

irritation characterized by repeated cycles of skin lesions, causing epidermal hyperplasia.

A1.9 Evaluation of effects on the environment

The environment can be polluted by accidental release of diesel fuel on a large scale, such as during tanker disasters and pipeline leaks, or on a smaller scale from contamination of soil around factories or garages. In water, diesel fuel spreads almost

immediately, polar and low-relative-molecular-mass components dissolve and leach out, volatile components evaporate from the water surface, and microbial degradation begins. The extent to which 'weathering' takes place depends on the temperature and on climatic conditions. The chemical composition of spills changes with time: after spillage on water, some fractions evaporate, and the evaporated diesel components are degraded photochemically; in sediment, diesel fuel appears

generally to be delivered to bottom sediments by settling particles;

in soil, the components of diesel fuel migrate at different rates, depending on the soil type.

The individual constituents of diesel fuel are inherently biodegradable, but the rates of biodegradation depend heavily on

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physical and climatic conditions and on microbial composition.

Aquatic organisms, in particular molluscs, bioaccumulate

hydro-carbons to varying extents, but the hydrocarbons are depurated on transfer to clean water. Diesel fuel may be bioaccumulated; no data are available about biomagnification.

Spills of diesel fuel have an immediate detrimental effect on the environment, causing substantial mortality of biota. Recolonization may occur after about one year, depending on the animal or plant species and the chemical and physical content of the spill residues.

Aquatic organisms that survive diesel fuel spills can be affected by external oil contamination and tissue accumulation: abnormal

development and altered metabolic rates are signs of the resulting stress.

A2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND ANALYTICAL METHODS

A2.1 Identity

Diesel fuels are a gas-oil fraction occurring during petroleum separation and commonly known as middle distillates (International Agency for Research on Cancer, 1989a). Gas oils are generally blended materials formulated to meet technical specifications (CONCAWE, in press). Commercial diesel fuels contain aliphatic, olefinic,

cycloparaffinic, and aromatic hydrocarbons (see section A2.1.1), and additives (see section A2.1.2) to improve their fuelling properties (Sandmeyer, 1981).

Four qualities of diesel fuel are available commercially: diesel fuel (general), diesel fuel No. 1, diesel fuel No. 2, and diesel fuel No. 4 (see Table 1). The composition of diesel fuels is comparable to that of heating oils (e.g. No. 1 and No. 2 fuel oils), except for the additives (International Agency for Research on Cancer, 1989a; Agency for Toxic Substances and Disease Registry, 1995).

Diesel fuel No. 2 is used mainly as automobile fuel and corresponds to diesel fuel (general). In Europe (countries of the European Union (EU) and European Free Trade Area (EFTA)), the

specifications for diesel fuel for transportation purposes are given in European standard EN 590 (European Committee for Standardization, 1993), which also provides for changes in the specifications to meet the requirements of different climatic conditions. In Sweden, two further qualities of on-road diesel fuel are available: environmental class 1 and class 2 (city diesel), with sulfur contents of 0.05% and 0.001%, respectively (Standardization Board in Sweden, 1991). The sulfur content of city diesel corresponds to that of kerosene. Diesel fuel for ship engines is covered by the International Standards

Organization (ISO) standard 8217 (International Standards

Organization, 1987). In the United States of America, three grades of diesel fuel are available: diesel fuel No. 1 (relatively high

volatility) for road vehicle engines subject to frequent speed and load changes; diesel fuel No. 2 (lower volatility) for industrial or heavy-duty, high-load engines running at uniform speed; and diesel fuel No. 4 (viscous) for low- and medium-speed engines such as those used in ships (American Society for Testing and Materials, 1988, 1992).

Several types of kerosene, also derived from the gas-oil fraction of petroleum separation, are used as aviation turbine fuels (JP fuels, jet fuels). Their hydrocarbon composition is comparable to that of diesel fuels.

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A2.1.1 Fuel components A2.1.1.1 Alkanes

Normal, branched, and cyclic alkanes (paraffins) are the most abundant components (about 65-85%) of diesel fuels. Pristane

(2,6,10,14-tetramethylpentadecane) and phytane (2,6,10,14-

tetramethyl-hexadecane) are of particular interest environmentally, as the ratios of pristane to heptadecane and of phytane to octadecane make it possible to identify the source of a fuel spill; furthermore, as these ratios increase during biological degradation, they can be used to estimate the age of an environmental contamination and the degree of elimination. Cycloalkanes and bicycloalkanes constitute a significant portion of the mixture, but individual compounds are present only at low levels and are difficult to analyse. Alkyl

derivatives of cyclopentane, cyclohexane, and cycloheptane are common components (Block et al., 1991; Table 2).

A2.1.1.2 Alkenes

Alkenes are not common components of crude oil but may be

present in diesel fuel if converted products are added after cracking.

These alkenes have predominantly branched and cyclic structures (Block et al., 1991). The total alkene content of diesel fuels is up to 10%

(CONCAWE, 1985) (see also Table 2).

A2.1.1.3 Aromatic compounds

Aromatic compounds constitute 5-30% of automotive diesel fuel, 5-40% of marine diesel fuel (CONCAWE, 1985), and 10-30% of diesel fuel No. 2 (Block et al., 1991). Table 2 shows the specifications of commercial diesel fuels in this regard.

Table 1. Synonyms and trade names of commercial diesel fuels

Name CAS CAS Registry Range of Synonyms name number carbon

numbers

Diesel fuel Diesel oil 68334-30-5 C9-C20a

Auto diesel, au (general) C10-C28b

diesel oil, DER diesel fuel oi oil, gas oil Diesel fuel Not assigned C9-C16c

Diesel fuel oil No. 1 (essentially C4-C16 (for diesel oil No.

equivalent to wide-cut diesel^d kerosene, aviation)^c

8008-20-6)

Diesel fuel No. 2 68476-34-6 Diesel fuel, d No. 2 diesel (applicable for oil No. 2, die fuel specific No. 2, No. 2 d viscosity

limits)

Diesel fuel 68476-31-3 C10-C30f

Marine diesel f No. 4 distillate mar fuel

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Adapted from International Agency for Research on Cancer (1989a) and suppleme

a From CONCAWE (in press)

b From CONCAWE (1985); automotive gas oil (automotive diesel fuel, DERV)

c From CONCAWE (1985, 1995)

d In Europe, fuels similar to US diesel No. 1 are commonly referred to as 'kerosene' or 'Arctic diesel'

e Term uncommon in Europe. In the United Kingdom, distillate fuels are frequ categorized as Class A1 (road diesel) and A2 (off-highway diesel)

f From CONCAWE (1985); distillate marine diesel

Only trace quantities of toxicologically relevant benzene, toluene, ethyl benzene, and xylene compounds (for physicochemical properties, see Table 6) are present in diesel fuel No. 2, but significant levels are found in diesel fuel No. 1 (Arctic diesel), which has lower flash-point specifications (Block et al., 1991); the International Agency for Research on Cancer (1989a) cites a

flash-point of 0.25-0.5%. The concentration of benzene in kerosenes is < 0.01% by volume; wide-cut aviation kerosenes may have higher

levels, but they are usually < 1% by volume (IPCS, 1986; CONCAWE, 1995; IPCS, 1993).

Table 2. Hydrocarbon specifications of some commercial diesel fuel oils

Specification Diesel Kerosene^b Distillate Di fuel^a marine fu diesel^c

Paraffins/naphthenes 65-95^e 78-96 60-90 (volume %) (wide-cut

aviation, < 1) n-Hexane (volume %) < 0.01

(wide-cut aviation, < 1)

Saturates (volume %) 59 Olefins (volume %) 0-10 0-5 0-10 0.

Aromatics (volume %) 5-30 4-25 5-40 23 (wide-cut

aviation, 6-25)

Aromaticity (weight %) 11