CARBON TETRACHLORIDE

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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 208

CARBON TETRACHLORIDE

First draft prepared by Ms J. de Fouw, National Institute of Public Health and the Environment, Bilthoven, the Netherlands

The layout and pagination of this pdf file and the printed EHC are not identical

Corrigenda published by November 2004 are incorporated in this file.

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 of the Inter-Organization Programme for the Sound Management of Chemicals.

World Health Organization Geneva, 1999

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The International Programme on Chemical Safety (IPCS), established in 1980, is a joint venture of the United Nations Environment Programme (UNEP), the International Labour Organisation (ILO), and the World Health Organization (WHO). The overall objectives of the IPCS are to establish the scientific basis for assessment of the risk to human health and the environment from exposure to chemicals, through international peer review processes, as a prerequisite for the promotion of chemical safety, and to provide technical assistance in strengthening national capacities for the sound management of chemicals.

The Inter-Organization Programme for the Sound Management of Chemicals (IOMC) was established in 1995 by UNEP, ILO, the Food and Agriculture Organization of the United Nations, WHO, the United Nations Industrial Development Organization, the United Nations Institute for Training and Research, and the Organisation for Economic Co-operation and Development (Participating Organizations), following recommendations made by the 1992 UN Conference on Environment and Development to strengthen cooperation and increase coordination in the field of chemical safety. The purpose of the IOMC is to promote coordination of the policies and activities pursued by the Participating Organizations, jointly or separately, to achieve the sound management of chemicals in relation to human health and the environment.

WHO Library Cataloguing in Publication Data Carbon tetrachloride.

(Environmental health criteria ; 208)

1.Carbon tetrachloride - toxicity 2.Environmental exposure I.International Programme on Chemical Safety II.Series

ISBN 92 4 157208 6 (NLM Classification: QD 305.H5) 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.

©World Health Organization 1999

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

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CONTENTS

ENVIRONMENTAL HEALTH CRITERIA FOR CARBON TETRACHLORIDE

PREAMBLE ix

ABBREVIATIONS xviii

1. SUMMARY 1

2. IDENTITY, PHYSICAL AND CHEMICAL

PROPERTIES, AND ANALYTICAL METHODS 6

2.1 Identity 6

2.2 Physical and chemical properties 7

2.3 Conversion factors 8

2.4 Analytical methods 8

2.4.1 Sampling and analysis in air 13 2.4.2 Sampling and analysis in water 13 2.4.3 Sampling and analysis in biological

samples 14

2.4.3.1 Blood and tissues 14

2.4.3.2 Urine 14

2.4.3.3 Fish 14

2.4.4 Sampling and analysis in foodstuffs 14

3. SOURCES OF HUMAN AND ENVIRONMENTAL

EXPOSURE 16

3.1 Natural occurrence 16

3.2 Anthropogenic sources 16

3.2.1 Production 16

3.2.1.1 Direct production and procedures 16

3.2.1.2 Indirect production 17

3.2.1.3 Emissions 18

3.2.2 Uses 18

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EHC 208: Carbon Tetrachloride

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iv

4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION

AND TRANSFORMATION 19

4.1 Transport and distribution between media 19

4.1.1 Transport 19

4.1.2 Distribution 19

4.1.3 Removal from the atmosphere; global

warming potential 21

4.1.4 Removal from water 22

4.1.5 Removal from soil 22

4.2 Abiotic degradation 22

4.2.1 Degradation in atmosphere 22

4.2.1.1 Photodegradation 22

4.2.1.2 Photolysis 23

4.2.1.3 Ozone-depletion potential 23

4.2.2 Degradation in water 24

4.2.3 Other degradation processes 24

4.3 Biotic degradation 24

4.3.1 Aerobic 24

4.3.2 Anaerobic 25

4.4 Bioaccumulation 26

5. CONCENTRATIONS IN THE ENVIRONMENT

AND EXPOSURE 28

5.1 Environmental levels 28

5.1.1 Air 28

5.1.2 Water 28

5.1.3 Soil and sediment 30

5.1.4 Biota 30

5.2 General population exposure 30

5.2.1 Outdoor air 30

5.2.2 Indoor air 30

5.2.3 Drinking-water 32

5.2.4 Foodstuffs 33

5.2.5 Intake averages 34

5.3 Occupational exposure 34

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v 6. KINETICS AND METABOLISM IN LABORATORY

ANIMALS AND HUMANS 36

6.1 Pharmacokinetics 36

6.1.1 Absorption 36

6.1.1.1 Oral 36

6.1.1.2 Dermal 37

6.1.1.3 Inhalation 37

6.1.2 Distribution 38

6.1.3 Elimination and fate 40

6.1.4 Physiologically based pharmacokinetic

modelling 42

6.2 Biotransformation and covalent binding of

metabolites 43

6.3 Human studies 48

6.3.1 Uptake 48

6.3.1.1 Dermal 48

6.3.1.2 Inhalation 49

6.3.2 Elimination 49

7. EFFECTS ON LABORATORY MAMMALS AND

IN VITRO TEST SYSTEMS 50

7.1 Single exposure 50

7.1.1 Lethality 50

7.1.2 Non-lethal effects 50

7.1.2.1 Oral exposure 50

7.1.2.2 Inhalation exposure 55

7.1.2.3 Subcutaneous and intraperitoneal

exposure 57

7.1.2.4 Dermal exposure 59

7.2 Short-term exposure 59

7.2.1 Oral exposure 59

7.2.2 Inhalation exposure 62

7.2.3 Intraperitoneal exposure 66

7.3 Long-term exposure 68

7.4 Irritation 70

7.4.1 Skin irritation 70

7.4.2 Eye irritation 70

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vi

7.5 Toxicity to the reproductive system,

embryotoxicity, teratogenicity 71

7.5.1 Reproduction 71

7.5.2 Embryotoxicity and teratogenicity 71

7.5.2.1 Oral exposure 72

7.5.2.2 Inhalation exposure 72

7.6 Mutagenicity 73

7.7 Carcinogenicity 83

7.7.1 Mice 83

7.7.2 Rats 85

7.8 Special studies 86

7.8.1 Immunotoxicity 86

7.8.2 Influence of oxygen levels 87

7.9 Factors modifying toxicity 88

7.9.1 Dosing vehicles 88

7.9.2 Diet 89

7.9.3 Alcohol 90

7.9.4 Enhancement of carbon tetrachloride- induced hepatotoxicity by various

compounds 93

7.9.5 Reduction of carbon tetrachloride-induced hepatotoxicity by various compounds 97

7.10 Mode of action 100

8. EFFECTS ON HUMANS 105

8.1 Controlled studies 105

8.1.1 Inhalation 105

8.1.2 Dermal 105

8.2 Case reports 106

8.3 Epidemiology 108

8.3.1 Non-cancer epidemiology 108

8.3.2 Cancer epidemiology 109

9. EFFECTS ON OTHER ORGANISMS IN THE

LABORATORY AND FIELD 113

9.1 Toxicity to microorganisms 113

9.2 Aquatic toxicity 113

9.2.1 Algae 113

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vii

9.2.2 Invertebrates 113

9.2.3 Vertebrates 118

9.3 Terrestrial toxicity 118

9.3.1 Earthworms 118

10. EVALUATION OF HUMAN HEALTH RISKS AND

EFFECTS ON THE ENVIRONMENT 120

10.1 Evaluation of human health risks 120

10.1.1 Exposure 120

10.1.2 Health effects 121

10.1.3 Approaches to health risk assessment 122 10.1.3.1 Calculation of a TDI based

on oral data 122

10.1.3.2 Calculation of a TC based

on inhalation data 123

10.1.3.3 Summary of the results of

risk assessment 124

10.1.3.4 Conclusions based on exposure and health risk assessment 124 10.2 Evaluation of effects on the environment 125

11. FURTHER RESEARCH 128

12. PREVIOUS EVALUATION BY INTERNATIONAL

BODIES 129

REFERENCES 130

RÉSUMÉ 166

RESUMEN 172

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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. + 41 22 – 9799111, fax no. + 41 22 – 7973460, E-mail irptc@unep.ch).

* * *

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.

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Environmental Health Criteria P R E A M B L E Objectives

In 1973 the WHO Environmental Health Criteria Programme was initiated 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 and since that time an ever- increasing number of assessments of chemicals and of physical effects have been produced. In addition, many EHC monographs have been devoted to evaluating toxicological methodology, e.g., for genetic, neurotoxic, teratogenic and nephrotoxic effects. Other publications have been concerned with epidemiological guidelines, evaluation of short-term tests for carcinogens, biomarkers, effects on the elderly and so forth.

Since its inauguration the EHC Programme has widened its scope, and the importance of environmental effects, in addition to health effects, has been increasingly emphasized in the total evaluation of chemicals.

The original impetus for the Programme came from World Health Assembly resolutions and the recommendations of the 1972 UN 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

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

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

Scope

The criteria monographs are intended to provide critical reviews on the effect on human health and the environment of chemicals and of combinations of chemicals and physical and biological agents. As such, they include and review studies that are of direct relevance for the evaluation. However, they do not describe every study carried out.

Worldwide data are used and are quoted from original studies, not from abstracts or reviews. Both published and unpublished reports are considered and it is incumbent on the authors to assess all the articles cited in the references. Preference is always given to published data. Unpublished data are only used when relevant published data are absent or when they are pivotal to the risk assessment. A detailed policy statement is available that describes the procedures used for unpublished proprietary data so that this information can be used in the evaluation without compromising its confidential nature (WHO (1990) Revised Guidelines for the Preparation of Environmental Health Criteria Monographs.

PCS/90.69, Geneva, World Health Organization).

In the evaluation of human health risks, sound human data, whenever available, are preferred to animal data. Animal and in vitro studies provide support and are used mainly to supply evidence missing from human studies. It is mandatory that research on human subjects is 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

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xi standard setting. These 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 field

• Evaluation of human health risks and effects on the environment

• Conclusions and recommendations for protection of human health and the environment

• Further research

• Previous evaluations by international bodies, e.g., IARC, JECFA, JMPR

Selection of chemicals

Since the inception of the EHC Programme, the IPCS has organized meetings of scientists to establish lists of priority chemicals for subsequent evaluation. Such meetings have been held in: Ispra, Italy, 1980; Oxford, United Kingdom, 1984; Berlin, Germany, 1987;

and North Carolina, USA, 1995. The selection of chemicals has been based on the following criteria: the existence of scientific evidence that the substance presents a hazard to human health and/or the environment; the possible use, persistence, accumulation or degradation of the substance shows that there may be significant human or environmental exposure; the size and nature of populations at risk (both human and other species) and risks for environment;

international concern, i.e. the substance is of major interest to several countries; adequate data on the hazards are available.

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If an EHC monograph is proposed for a chemical not on the priority list, the IPCS Secretariat consults with the Cooperating Organizations and all the Participating Institutions before embarking on the preparation of the monograph.

Procedures

The order of procedures that result in the publication of an EHC monograph is shown in the 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 layout and language. The first draft, prepared by consultants or, more usually, staff from 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 document acceptable as a first draft, it is distributed, in its unedited form, to well over 150 EHC contact points throughout the world who are asked to comment on its completeness and accuracy and, where necessary, 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 some four months are allowed before the comments are considered by the RO and author(s). A second draft incorporating comments received and approved by the Director, IPCS, is then distributed to Task Group members, who carry out the 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 health and environmental risks from exposure to the chemical. A summary and recommendations for further research and improved safety aspects are also required. The composition of the Task Group is dictated by the range of expertise required for the subject of the meeting and by the need for a balanced geographical distribution.

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Commitment to draft EHC Commitment to draft EHC

Document preparation initiated

Draft sent to IPCS Responsible Officer (RO)

EHC PREPARATION FLOW CHART

Revision as necessary

Possible meeting of a few experts to resolve controversial issues

First Draft First Draft

Responsible Officer, Editor check for coherence of text and readability (not language editing)

International circulation to Contact Points (150+)

Comments to IPCS (RO)

Review of comments, reference cross-check;

preparation of Task Group (TG) draft

Task Group meeting

Insertion of TG changes

Post-TG draft; detailed reference cross-check

Editing Editing

Word-processing

Camera-ready copy

Final editing

Approval by Director, IPCS

WHO Publication Office

Printer Proofs PublicationPublication Graphics

Library for CIP Data French/Spanish translations of Summary

Working group, if required Editor

routine procedure optional procedure

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The three cooperating organizations of the IPCS recognize the important role played by nongovernmental organizations.

Representatives from relevant national and international associations may be invited to join the Task Group as observers. While observers may provide a valuable contribution to the process, they can only speak at the invitation of the Chairperson. Observers do not participate in the final evaluation of the chemical; this is the sole responsibility of the Task Group members. When the Task Group considers it to be appropriate, it may meet in camera.

All individuals who as authors, consultants or advisers participate in the preparation of the EHC monograph 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 conflict of interest statement. Such a 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 then goes for language editing, reference checking, and preparation of camera-ready copy. 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 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 for health or environmental effects of the agent because of greater exposure; an appreciable time period has elapsed since the last evaluation.

All Participating Institutions are informed, through the EHC progress report, of the authors and institutions proposed for the drafting 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.

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WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR CARBON TETRACHLORIDE

Members

Dr D. Anderson, British Industry Biological Research Association (BIBRA) Toxicology International, Carshalton, Surrey, United Kingdom (Chairperson)

Dr E. Elovaara, Finnish Institute for Occupational Health, Helsinki,

Finland

Dr E. Frantik, National Institute of Public Health, Center of Industrial Hygiene and Occupational Diseases, Prague, Czech Republic

Dr B. Gilbert, Ministry of Health, Far-Manguinhas-FIOCRUZ, Rio de Janeiro, Brazil (Co-Rapporteur)

Mr M. Greenberg, National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, North Carolina, USA

Mr P. Howe, Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, United Kingdom

Professor H. Kappus, Virchow Klinikum der Humboldt Universitat, Berlin, Germany

Dr D. McGregor, Unit of Carcinogen Identification and Evaluation, International Agency for Research on Cancer, Lyon, France (Co-Rapporteur)

Dr P. Parsons, Health and Safety Executive, Bootle, Merseyside, United Kingdom

Professor J.A. Sokal, Institute of Occupational Medicine and Environmental Health, Sosnowiec, Poland

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Secretariat

Dr J. de Fouw, Centre for Substances and Risk Assessment, National Institute of Public Health and the Environment, Bilthoven, The Netherlands

Professor F. Valiƒ, IPCS Scientific Adviser, Andrija Štampar School of Public Health, Zagreb University, Zagreb, Croatia (Responsible Officer and Secretary of Meeting)

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ENVIRONMENTAL HEALTH CRITERIA FOR CARBON TETRACHLORIDE

A Task Group on Environmental Health Criteria for Carbon Tetrachloride met at the British Industrial and Biological Research Association (BIBRA), Carshalton, United Kingdom, from 2 to 6 March 1998. Dr D. Anderson, welcomed the participants on behalf of the host institution, and Professor F. Valiƒ opened the Meeting on behalf of the heads of the three cooperating organizations of the IPCS (UNEP/ILO/WHO). The Task Group reviewed and revised the draft monograph and made an evaluation of the risks for human health from exposure to carbon tetrachloride.

The first draft of this monograph was prepared by Ms J. de Fouw, Centre for Substances and Risk Assessment, National Institute of Public Health and the Environment, Bilthoven, the Netherlands.

Professor Valiƒ, Zagreb University, Croatia, was responsible for the overall scientific content of the monograph and for the organization of the Meeting, and Dr P.G. Jenkins, IPCS Central Unit, for the technical editing of the monograph.

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

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ABBREVIATIONS

ALAT alanine aminotransferase AP alkaline phosphatase ASAT aspartate aminotransferase ATPase adenosine triphosphatase

ATSDR Agency for Toxic Substances and Disease Registry CNS central nervous system

CPK creatine phosphokinase CYP cytochrome P-450

Hb haemoglobin

Ht haematocrit

ip intraperitoneal LDH lactate dehydrogenase

LOAEL lowest-observed-adverse-effect level MPV mean packed volume

NADPH reduced nicotinamide adenine dinucleotide phosphate NIOSH National Institute for Occupational Safety and Health

(USA)

NOAEL no-observed-adverse-effect level PBB polybrominated biphenyl PCB polychlorinated biphenyl RBC red blood cell

SDH sorbitol dehydrogenase SRBC sheep red blood cells TC tolerable concentration TDI tolerable daily intake

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1

1. SUMMARY

Carbon tetrachloride is a clear, colourless, volatile liquid with a characteristic, sweet odour. It is miscible with most aliphatic solvents and is itself a solvent. The solubility in water is low. Carbon tetrachloride is non-flammable and is stable in the presence of air and light. Decomposition may produce phosgene, carbon dioxide and hydrochloric acid.

The source of carbon tetrachloride in the environment is likely to be almost exclusively anthropogenic in origin. Most of the carbon tetrachloride produced is used in the production of chlorofluorocarbons (CFCs) and other chlorinated hydrocarbons. The global production of carbon tetrachloride amounted to 960 000 tonnes in 1987. However, since the Montreal Protocol on Substances that Deplete the Ozone Layer (1987) and its amendments (1990 and 1992) have established a timetable for the phase-out of the production and consumption of carbon tetrachloride, manufacture has dropped and will continue to drop.

Several sufficiently sensitive and accurate analytical methods for determining carbon tetrachloride in air, water and biological samples have been developed. The majority of these methods are based on direct injection into a gas chromatograph or adsorption on activated charcoal, then desorption or evaporation and subsequent gas chromatographic detection.

Nearly all carbon tetrachloride released to the environment will ultimately be present in the atmosphere, owing to its volatility. Since the atmospheric residence time of carbon tetrachloride is long, it is widely distributed. During the period 1980–1990, atmospheric levels were around 0.5–1.0 :g/m³. Estimates of atmospheric lifetime are variable, but 45–50 years is accepted as the most reasonable value.

Carbon tetrachloride contributes both to ozone depletion and to global warming. It is in general resistant to aerobic biodegradation but less so to anaerobic. Acclimation increases biodegradation rates. Although the octanol-water partition coefficient indicates moderate potential for bioaccumulation, short tissue lifetime reduces this tendency.

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2

In water, reports have indicated levels of less than 10 ng/litre in the ocean and generally less than 1 :g/litre in fresh water, but much higher values close to release sites. Levels of up to 60 :g/kg have been recorded in foods processed with carbon tetrachloride, but this practice has now ceased.

The general population is exposed to carbon tetrachloride mainly via air. On the basis of the reported concentrations in ambient air, foodstuffs and drinking-water, a daily carbon tetrachloride intake of around 1 :g/kg body weight has been estimated. This estimate is probably rather high for the present day, because the use of carbon tetrachloride as a fumigant of grain has stopped and the carbon tetrachloride values reported for food and used in the calculation were especially those found in fatty and grain-based foods. Values of 0.1 to 0.27 :g/kg body weight for daily exposure of the general population have been reported elsewhere. Exposure to higher levels of carbon tetrachloride can occur in the workplace as a result of accidental spillage.

Carbon tetrachloride is well absorbed from the gastrointestinal and respiratory tract in animals and humans. Dermal absorption of liquid carbon tetrachloride is possible, but dermal absorption of the vapour is slow.

Carbon tetrachloride is distributed throughout the whole body, with highest concentrations in liver, brain, kidney, muscle, fat and blood. The parent compound is eliminated primarily in exhaled air, while minimal amounts are excreted in the faeces and urine.

The first step in the biotransformation of carbon tetrachloride is catalysed by cytochrome P-450 enzymes, leading to the formation of the reactive trichloromethyl radical. Oxidative biotransformation is the most important pathway in the elimination of the radical, forming the even more reactive trichloromethylperoxyl radical, which can react further to form phosgene. Phosgene may be detoxified by reaction with water to produce carbon dioxide or with glutathione or cysteine. Formation of chloroform and dichlorocarbene occurs under anaerobic conditions.

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Summary ________________________________________________________

3 Covalent binding to macromolecules and lipid peroxidation occur via metabolic intermediates of carbon tetrachloride.

The liver and kidney are target organs for carbon tetrachloride toxicity. The severity of the effects on the liver depends on a number of factors such as species susceptibility, route and mode of exposure, diet or co-exposure to other compounds, in particular ethanol.

Furthermore, it appears that pretreatment with various compounds, such as phenobarbital and vitamin A, enhances hepatotoxicity, while other compounds, such as vitamin E, reduce the hepatotoxic action of carbon tetrachloride.

Moderate irritation after dermal application was seen on the skins of rabbits and guinea-pigs, and there was a mild reaction after application into the rabbit eye.

The lowest LD50 of 2391 mg/kg body weight (14-day period) was reported in a study on dogs involving intraperitoneal administration.

In rats the LD50 values ranged from 2821 to 10 054 mg/kg body weight.

In a 12-week oral study on rats (5 days/week), the no-observed- adverse-effect level (NOAEL) was 1 mg/kg body weight. The lowest- observed-adverse-effect level (LOAEL) reported in this study was 10 mg/kg body weight, showing a slight, but significant increase in sorbitol dehydrogenase (SDH) activity and mild hepatic centrilobular vacuolization. A similar NOAEL of 1.2 mg/kg body weight (5 days/

week) was found in a 90-day oral study on mice, with a LOAEL of 12 mg/kg body weight, where hepatotoxicity occurred.

When rats were exposed to carbon tetrachloride by inhalation for approximately 6 months, 5 days/week, 7 h/day, a NOAEL of 32 mg/m³ was reported. The LOAEL, based on changes in the liver morphology, was reported to be 63 mg/m³. In another 90-day study on rats, a NOAEL of 6.1 mg/m³ was found after continuous exposure to carbon tetrachloride. The lowest exposure level of 32 mg/m³ (the lowest concentration studied) in a 2-year inhalation study on rats caused marginal effects.

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4

The only oral long-term toxicity study available was a 2-year study in rats, which were exposed to 0, 80 or 200 mg carbon tetrachloride/kg feed. Owing to chronic respiratory disease in all animals beginning at 14 months, which resulted in increased mortality, the results reported upon necropsy at 2 years are inadequate for a health risk evaluation.

It was concluded that carbon tetrachloride can induce embryo- toxic and embryolethal effects, but only at doses that are maternally toxic, as observed in inhalation studies in rats and mice. Carbon tetrachloride is not teratogenic.

Many genotoxicity assays have been conducted with carbon tetrachloride. On the basis of available data, carbon tetrachloride can be considered as a non-genotoxic compound.

Carbon tetrachloride induces hepatomas and hepatocellular carcinomas in mice and rats. The doses inducing hepatic tumours are higher than those inducing cell toxicity.

In humans, acute symptoms after carbon tetrachloride exposure are independent of the route of intake and are characterized by gastrointestinal and neurological symptoms, such as nausea, vomiting, headache, dizziness, dyspnoea and death. Liver damage appears after 24 h or more. Kidney damage is evident often only 2 to 3 weeks following the poisoning.

Epidemiological studies have not established an association between carbon tetrachloride exposure and increased risk of mortality, neoplasia or liver disease. Some studies have suggested an association with increased risk of non-Hodgkin’s lymphoma and, in one study, with mortality and liver cirrhosis. However, not all of these studies pinpointed specific exposure to carbon tetrachloride, and the statistical associations were not strong.

In general carbon tetrachloride appears to be of low toxicity to bacteria, protozoa and algae; the lowest toxic concentration reported was for methanogenic bacteria with an IC50 of 6.4 mg/litre. For aquatic invertebrates acute LC50 values range from 28 to > 770

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Summary ________________________________________________________

5 mg/litre. In freshwater fish the lowest acute LC50 value of 13 mg/litre was found in the golden orfe (Leuciscus idus melanotus), and for marine species an LC50 value of 50 mg/litre was reported for the dab (Limanda limanda). Carbon tetrachloride appears to be more toxic to embryo-larval stages of fish and amphibians than to adults. The common bullfrog (Rana catesbeiara) is the most susceptible species, the LC50 being 0.92 mg/litre (fertilization to 4 days after hatching).

The available data indicate that hepatic tumours are induced by a non-genotoxic mechanism, and it therefore seems acceptable to develop a tolerable daily intake (TDI) and a tolerable daily concentration in air (TC) for carbon tetrachloride.

On the basis of the study of Bruckner et al. (1986), in which a NOAEL of 1 mg/kg body weight was observed in a 12-week oral study on rats, and incorporating a conversion factor of 5/7 for daily dosing and applying an uncertainty factor of 500 (100 for inter- and intraspecies variation, 10 for duration of the study, and modifying factor 0.5 because it was a bolus study), a TDI of 1.42 :g/kg body weight is obtained.

On the basis of a 90-day inhalation study on rats (Prendergast et al., 1967), in which a NOAEL of 6.1 mg/m³ was reported, a TC of 6.1 :g/m³ was calculated using the factors 7/24 and 5/7 to convert to continuous exposure and an uncertainty factor of 1000 (100 for inter- and intraspecies variation and 10 for the duration of the study). This TC corresponds to a TDI of 0.85 :g/kg body weight.

Comparing the estimated upper limit of prevailing human daily intake of 0.2 :g/kg body weight with the lowest TDI value (0.85 :g/kg body weight), the conclusion can be drawn that the currently prevailing exposure of the general population to carbon tetrachloride from all sources is unlikely to cause excessive intake of the chemical.

In general, the risk to aquatic organisms from carbon tetrachloride is low. However, it may present a risk to embryo-larval stages at, or near, sites of industrial discharges or spills.

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6

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

2.1 Identity

Chemical formula: CCl4

Chemical structure:

C l

C l C C l

Common name: carbon tetrachloride Common synonyms: Carbona, carbon chloride,

tetrachloromethane, carbon tet, methane tetrachloride, perchloromethane, tetrachlorocarbon

Trade names: Benzinoform, Fasciolin, Flukoids, Freon 10, Halon 104, Necatorina, Necatorine, Tetrafinol, Tetraform, Tetrasol, Univerm, Vermoestricid CAS chemical name: tetrachloromethane

CAS registry number: 56-23-5 RTECS registry number: FG 4900000

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Identity, Physical and Chemical Properties, and Analytical Methods ______________________________________________________

7

2.2 Physical and chemical properties

The most important physical properties of carbon tetrachloride are given in Table 1.

Table 1. Physical properties of carbon tetrachloride^a

Colour colourless

Relative molecular mass 153.8

Boiling point at 101.3 kPa, 20/C 76.72 /C Melting point at 101.3 kPa, 20 /C !22.92 /C

Density (25 /C) 1.594 g/ml

Density of solid at !186 /C 1831 kg/m³

!80 /C 1809 kg/m³

Refractive index at 20 /C 1.4607

Vapour pressure at 20 /C 91.3 mmHg; 12.2 kPa

at 0 /C 32.9 mmHg; 4.4 kPa

Autoignition temperature > 1000 /C

Critical pressure 4.6 MPa

Critical temperature 283.2 /C

Solubility in water at 25 /C 785 mg/litre Solubility of water in carbon tetrachloride

at 25 /C

0.13 g/kg

Henry's law constant at 24.8 /C 2.3 × 10^-2 atm-m³/mol

Heat of evaporation 194.7 kJ/kg

Log K_ow 2.64

Log K_oc 2.04

a From Kenaga (1980); US EPA (1984b); Huiskamp et al. (1986); ATSDR (1994).

Carbon tetrachloride is a volatile colourless clear heavy liquid with a characteristic sweet non-irritant odour. The odour threshold in water is 0.52 mg/litre and in air is > 10 ppm. Carbon tetrachloride is miscible with most aliphatic solvents and it is a solvent for benzyl resins, bitumen, chlorinated rubber, rubber-based gums, oils and fats.

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________________________________________________________

8

The chemical is non-flammable and fairly stable in the presence of air and light. Upon heating by a flame or hot metal surface in air, toxic phosgene is produced. Thermal dissociation in the absence of air proceeds slowly at about 400 /C and is extensive at temperatures ranging from 900 to 1300 /C with the formation of perchloroethylene, hexachloroethane and some molecular chlorine. A mixture of carbon tetrachloride and excess of water vapour decomposes at 250 /C to carbon dioxide and hydrochloric acid. When the amount of water in the mixture is limited, phosgene will be formed too. This decomposition also occurs when moist or wet carbon tetrachloride is exposed to UV radiation (253.7 nm). Like other chloromethanes, carbon tetrachloride reacts (sometimes explosively) with aluminium and its alloys.

Similar violent reaction may occur with metals, such as barium, magnesium and zinc, boranes and silanes, and, in the presence of peroxides or light, with unsaturated compounds (such as ethene).

Carbon tetrachloride may be reduced to chloroform when treated with zinc and acid, and to methane when treated with potassium amalgam and water (Huiskamp et al., 1986).

2.3 Conversion factors

1 mg carbon tetrachloride/m³ air = 0.156 ppm at 20 /C and 101.3 kPa (760 mmHg)

1 ppm = 6.41 mg carbon tetrachloride/m³ 2.4 Analytical methods

Procedures used for the sampling and determination of carbon tetrachloride in different media are summarized in Table 2.

The preferred analytical technique is gas chromatography (GC) using either electron capture detection (ECD), ion trap detection, flame or photo ionisation detection or mass spectrometry. Only one method, reported by Lioy & Lioy (1983), depends on the use of MIRAN-infrared spectrometry, a method of very poor sensitivity.

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Table 2. Sampling and analysis of carbon tetrachloride^a

Medium Sampling method Analytical method Detection limit Sample size Comments Reference

Air aspiration velocity: 28 l/min optical path: 20 m

MIRAN infrared spectrometry

400 :g/m³ Lioy & Lioy,

1983

Air direct injection GC with 2 ECD’s

in series

0.4 :g/m³ (estimated)

8 ml injected Lillian & Singh,

1974

Air direct injection GC – ECD 0.2 :g/m³ 2 ml injected BIT-SC, 1976

Air direct injection GC – ECD 0.06 :g/m³ 5 ml injected Lasa et al.,

1979 Air direct injection, methane

added

GC – ECD 0.01 :g/m³ 12 ml injected thorough purification of carrier gas and apparatus required

Makide &

Yokohata, 1983 Air adsorption on Porapak-N liquid

desorption (methanol)

GC – ECD 1 :g/m³ 20 litres advantage of using methanol over CS₂ is the absence of a background signal in the ECD

Van Tassel et al., 1981

Air adsorption on activated charcoal, liquid desorption (ethanol) trichloroethylene used as IS

adsorption on activated charcoal liquid desorption (CS2) methylcyclohexane used as IS

GC – ECD

GC – FID

0.2 :g

ca. 0.15 mg (detector sensitivity)

up to 30 litres can be sampled

activated charcoal shown to be more efficient trapping material than XADs, Tenax or Chromosorbs

Morele et al., 1989

Air adsorption on activated charcoal, liquid desorption (CS₂)

GC – FID 0.01 mg 5–15 litres NIOSH, 1977,

1984

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Medium Sampling method Analytical method Detection limit Sample size Comments Reference Air adsorption on Chromosorb 102

or Silicone OV 101 (at

!³⁵/C), thermal desorption

GC – ECD 0.003 :g/m³ 20 ml Makide et al.,

1979 Air adsorption on Porapak-N,

thermal desorption at 200 /C

GC – ECD 0.005 :g/m³ 0.3–3 litres confirmation of results by use of GC – MS

Russell &

Shadoff, 1977 Air adsorption on Chromosorb

102, thermal desorption at 200 /C

GC – ECD (collection tube already connected to GC)

0.01 :g/m³ (estimated)

1 litre Elias, 1977

Air adsorption on Carbopak-B at 78 /C, thermal desorption

GC – ECD 0.01 :g/m³ 1 litre calibration with permeation tubes

Crescentini et al., 1981 Air adsorption on Chromosorb-102

and activated charcoal, thermal desorption at 150 /^C

GC – ECD – FID (2 detectors in parallel)

ca. 0.06 :g/m³ 1–3 litres Heil et al.,

1979 Air adsorption on Tenax-GC,

GC – MS 0.2 :g/m³ 20 litres compounds were

cryofocused

Krost et al., 1982 Air adsorption on Carbopak-C,

GC – MS 0.1 :g/m³ 300 ml Crescentini et

al., 1983 Air adsorption on activated

charcoal, liquid desorption (5%

CS₂ in methanol)

GC – ECD followed by a PID

0.7 :g/m³ 24 h sample Coutant &

Scott, 1982 Air cold trap (liquid oxygen),

heating

GC – ECD 0.006 :g/m³ 30 ml aliquot in trap

measurement of air samples from the stratosphere

Harsch &

Cronn, 1978

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Air injection in cold trap, heating GC – MS (SIM) 0.04 :g/m³ 100 ml Cronn &

Harsch, 1979 Air cold trap (!¹⁷³/C), heating to

257 /^C GC – PID – ECD –

FID (3 detectors in series)

0.006 :g/m³ 0.5–1.7 litres column is kept at !¹⁰³/^C (cryofocusing)

Rudolph &

Jebsen, 1983 Water dibromomethane used as IS GC – ECD 0.001 :g/litre 500 :l injected suitable for routine analysis

of river waters

Herzfeld et al., 1989

Water direct aqueous injection GC – MS (SIM) 2 :g/litre 10 :l injected Fujii, 1977

Water direct aqueous injection GC – ECD 0.015 :g/litre 2 :l injected suitable for halocarbons in water in the 0.01 to 10 :g/litre range

Grob, 1984

Water direct aqueous injection, water removal by permeaselective membrane

GC – ECD 0.05 :g/litre 5–20 :l injected

Simmonds &

Kerns, 1979 Water liquid-liquid extraction (using

hexane)

GC – ECD 0.10 :g/litre 10–20 ml Van Rensburg

et al., 1978 Water liquid-liquid extraction (using

xylene)

GC – ECD 0.2 :g/litre Inoko et al.,

1984 Water liquid-liquid extraction (using

pentane)

GC – ECD 0.05 :g/litre Kroneld, 1985

Water purge and trap technique, thermal desorption, fluorobenzene as IS

GC – ITD 0.1 :g/litre 5 ml Eichelberger et

al., 1990

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Medium Sampling method Analytical method Detection limit Sample size Comments Reference Grain codistillation of carbon

tetrachloride in food sample and mixture of 1,2- dichloropropane and 1,2- dibromopropane as IS in hexane

GC – ECD 1 :g/kg De Vries et al.,

1985

Adipose tissue

purge and trap technique (Tenax-silica gel), thermal desorption

GC – MS < 1.3 :g/litre 200–500 mg liquefied fat samples

Peoples et al., 1979 Blood purge and trap technique

(Tenax-silica gel), thermal desorption

GC – MS < 1.3 :g/litre 0.5 ml water- serum sample

Peoples et al., 1979 Blood warming and passing an inert

gas, vapours trapped on Tenax-GC, thermal desorption

GC – MS 3 :g/litre 10 ml sample Pellizzari et al.,

1985 Urine liquid-liquid extraction using

pentane (adding 2.6 g ammonium carbonate)

GC – ECD (20%

SP-2100/0.1%

Carbowax 1500 column)

< 1 :g/litre 10 ml sample Youssefi et al.,

1978

Fish extraction with pentane and isopropanol, with bromotri- chloromethane used as IS

GC – ECD 0.1 :g/kg in fresh material

Baumann Ofstad et al., 1981

aAbbreviations: GC = gas chromatography; MS = mass spectrometry; ECD = electron capture detector; SIM = single (selected) ion monitoring;

FID = flame ionisation detector; ITD = ion trap detector; PID = photo ionisation detector; IS = internal standard.

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13 2.4.1 Sampling and analysis in air

Methods reported in Table 2 for detecting carbon tetrachloride in air are of four types.

a) Direct measurement

These methods are simple, because the air is aspirated or injected directly into the measuring instrument, but they can only be used when carbon tetrachloride is present in the air at relatively high levels.

b) Adsorption – liquid desorption

In this type of method, air samples are passed through an activated adsorbing agent. The adsorbed carbon tetrachloride is desorbed with an appropriate solvent and then passed through the gas chromatograph. Activated carbon has been described as superior to other adsorbents for adsorption. Elution from the carbon is achieved with carbon disulfide (Morele et al., 1989; ATSDR, 1994).

c) Adsorption – thermal desorption

After adsorption on an activated adsorbing agent, the carbon tetrachloride is thermally desorbed and driven into the gas chromatograph.

d) Cold trap – heating

In this type of procedure, air samples are injected into a cold trap. The trap is then heated and the carbon tetrachloride content transferred into the column of a gas chromatograph.

2.4.2 Sampling and analysis in water

Several methods for sampling analysing the carbon tetrachloride content in water are included in Table 2. Most of these methods are based on direct injection techniques or on liquid-liquid extraction by means of a non-polar non-halogenated solvent.

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2.4.3 Sampling and analysis in biological samples 2.4.3.1 Blood and tissues

Peoples et al. (1979) developed a method to determine carbon tetrachloride in adipose tissue and blood. In both cases the carbon tetrachloride is purged and trapped on Tenax-silica gel and determined by mass spectrometry after thermal desorption.

Pellizzari et al. (1985) similarly passed an inert gas over a warmed plasma sample with adsorption of the vapour on a Tenax- GC cartridge, and then recovered the carbon tetrachloride by thermal desorption.

2.4.3.2 Urine

The only method listed in Table 2 for measuring carbon tetrachloride concentrations in urine is based on an extraction technique with pentane and direct gas chromatographic analysis of the pentane extract (Youssefi et al., 1978).

2.4.3.3 Fish

Baumann Ofstad et al. (1981) developed a method for the analysis of volatile halogenated hydrocarbons in biological samples and used this method for the analysis of fish samples. It should be noted that the identification and quantification of carbon tetrachloride is especially vulnerable to contamination, so the practical usefulness of this method is very limited.

2.4.4 Sampling and analysis in foodstuffs

A method for the determination of 22 compounds (including carbon tetrachloride) in a variety of foods was described by Daft (1988). In this method the samples are extracted with isooctane, and cleaned up according to fat content and food type. Most samples (6–10 :l) are injected for GC with ECD and Hall-electron conductivity detection immediately following the initial extraction or dilution.

De Vries et al. (1985) provided a method for analysis of carbon tetrachloride in grain and grain-based products containing 1–2000 :g/kg. A food sample is mixed with water and an internal standard

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15 mixture of 1,2-dichloropropane and 1,2-dibromopropane is added.

The water is then distilled until 1 ml has been collected under hexane. The hexane is then separated, dried and injected (2 :l) into the GC column.

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16

3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

3.1 Natural occurrence

It has been suggested that carbon tetrachloride can be formed in the troposphere by the solar-induced photochemical reactions of chlorinated alkenes (Singh et al., 1975). However, so far this reaction has only been demonstrated in the laboratory, and, even if it could happen in nature, it is not certain that it would be a major source of environmental carbon tetrachloride. Carbon tetrachloride has been detected in volcanic emission gases (Isidorov et al., 1990). Several studies have shown that global atmospheric levels of carbon tetrachloride can be explained by anthropogenic sources alone (Singh et al., 1976).

3.2 Anthropogenic sources

3.2.1 Production

3.2.1.1 Direct production and procedures

Production of carbon tetrachloride began in about 1907 in the USA. It can be produced by chlorination of methane, methanol, carbon disulfide, propane, 1,2-dichloroethane and higher hydrocarbons.

The world production of carbon tetrachloride ranged from 850 to 960 kilotonnes over the years 1980–1988. Table 3 provides some data on past production and production capacities of carbon tetrachloride. These data are based on information in the ECDIN database (ECDIN, 1992) and BUA-Stoffbericht 45 (BUA, 1990).

Since 1990 the production of carbon tetrachloride has dropped.

The Montreal Protocol of 1990 and its subsequent amendments established the phase-out by 1996 of production and use of carbon tetrachloride and of chlorofluorocarbons (CFCs) by major manufacturing countries. Special conditions were allowed for developing countries, where consumption of controlled substances under Annex B (including carbon tetrachloride) was required to be reduced by 85%

of its 1998–2000 average level (or a calculated consumption level of

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Sources of Human and Environmental Exposure ________________________________________________________

17 0.2 kg per capita, whichever is lower) by 2005 and completely stopped by 2010 (UNEP, 1996).

Table 3. Past production and production capacity of carbon tetrachloride

Country Year Production

(in kilotonnes)

Capacity (in kilotonnes)

France 1988 – 90

Italy 1987

1988

95 –

– 130 Germany (former FRG) 1985

1987 1988

150 180 170

– – 180

EEC 1985 – 520

1987 480 –

1988 478 540

Japan 1985 – 72

1987 52 –

1988 – 70

United Kingdom 1988 – 75

USA 1986 286 –

1987 340 –

1988 – 281

1991 143 –

World 1985 – 1200

1987 960 –

1988 – 1100

3.2.1.2 Indirect production

Carbon tetrachloride can be produced as a by-product during the manufacture of other products and compounds (US EPA, 1984a) and during wood pulp bleaching.

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18 3.2.1.3 Emissions

According to US EPA (1991), in 1989 approximately 2000 tonnes of carbon tetrachloride were released during manufacturing and processing to the air in the USA. US EPA (1984a) reported emission factors for carbon tetrachloride arising during the chlorination of hydrocarbons ranging from 0.9 kg/tonne of carbon tetrachloride (controlled) to 2.8 kg/tonne of carbon tetrachloride (uncontrolled). Furthermore, emissions may result from industrial water treatment or from old landfill sites.

3.2.2 Uses

Most of the carbon tetrachloride produced is used in the production of CFCs, which were primarily used as refrigerants, propellants, foam-blowing agents and solvents and in the production of other chlorinated hydrocarbons.

The use of carbon tetrachloride increased in the EEC as well as in the USA during the years 1980–1987. However, this use has decreased in recent years due to the Copenhagen Amendment to the Montreal Protocol (1992) (UNEP, 1996). A survey in Japan could detect no use of carbon tetrachloride in small to medium scale industries in 1996 (Ukai et al., 1997).

Carbon tetrachloride has been used as a grain fumigant, pesticide, solvent for oils and fats, metal degreaser, fire extinguisher and flame retardant, and in the production of paint, ink, plastics, semi-conductors and petrol additives. It was previously also widely used as a cleaning agent. All these uses have tended to be phased-out as production has dropped (ECDIN, 1992; ATSDR, 1994).

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19

4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION

4.1 Transport and distribution between media

4.1.1 Transport

Carbon tetrachloride introduced into water resources is trans- ported by movement of surface water and groundwater. Because of its volatility, evaporation is considered to be the main process for the removal of carbon tetrachloride from aquatic systems. The amount of carbon tetrachloride dissolved in the oceans is reported to be less than 1–3% of that in the atmosphere (Galbally, 1976; Singh et al., 1976).

Practically all the carbon tetrachloride released to the environment is thus present in the atmosphere (US EPA, 1991). Because carbon tetrachloride does not degrade readily in the atmosphere, significant global transport is expected.

Following releases to soil, most carbon tetrachloride is expected to evaporate rapidly due to its high vapour pressure. A small fraction of carbon tetrachloride may adsorb to organic matter, based on a calculated soil adsorption coefficient of 100 (log Koc = 2.04) (Kenaga, 1980).

Walton et al. (1992) studied the adsorption of carbon tetrachloride from solution onto two soils, a silt loam (1.49% organic carbon) and a sandy loam (0.66% organic carbon). The soil was shaken with several concentrations of carbon tetrachloride (100 to 650 mg/kg soil) for 18 h. The Koc values determined were 143.6 for the silt loam and 48.9 for the sandy loam. Duffy et al. (1997) studied the downward movement of carbon tetrachloride in 3 horizons of a fine montmorillonitic soil. Koc values of 55, 77.6 and 269 were calculated for the modern A, buried A and loess C soil horizons. However, the authors point out that Koc values are unreliable in soils with low organic carbon and high clay content. Therefore, the highest Koc value should be treated with some caution.

4.1.2 Distribution

The evidence that the residence time of carbon tetrachloride in the atmosphere is long (see section 4.1.3) and that nearly all of the