Asbestos and other natural mineral fibres



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INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY

ENVIRONMENTAL HEALTH CRITERIA 53

ASBESTOS AND OTHER NATURAL MINERAL FIBRES

This report contains the collective views of an international group of

experts and does not necessarily represent the decisions or the stated

policy of the United Nations Environment Programme, the International

Labour Organisation, or the World Health Organization.
Published under the joint sponsorship of

the United Nations Environment Programme,

the International Labour Organisation,

and the World Health Organization


World Health Orgnization

Geneva, 1986

The International Programme on Chemical Safety (IPCS) is a

joint venture of the United Nations Environment Programme, the

International Labour Organisation, and the World Health

Organization. The main objective of the IPCS is to carry out and

disseminate evaluations of the effects of chemicals on human health

and the quality of the environment. Supporting activities include

the development of epidemiological, experimental laboratory, and

risk-assessment methods that could produce internationally

comparable results, and the development of manpower in the field of

toxicology. Other activities carried out by the IPCS include the

development of know-how for coping with chemical accidents,

coordination of laboratory testing and epidemiological studies, and

promotion of research on the mechanisms of the biological action of

chemicals.

ISBN 92 4 154193 8
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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 1986
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

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whatsoever on the part of the Secretariat of the World Health

Organization concerning the legal status of any country, territory,

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The mention of specific companies or of certain manufacturers'

products does not imply that they are endorsed or recommended by the

World Health Organization in preference to others of a similar

nature that are not mentioned. Errors and omissions excepted, the

names of proprietary products are distinguished by initial capital

letters.

CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR ASBESTOS AND OTHER NATURAL

MINERAL FIBRES


1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary

1.1.1. Identity; physical and chemical properties,

methods of sampling and analysis



1.1.2. Sources of occupational and environmental exposure

1.1.3. Environmental levels and exposures

1.1.4. Toxicological effects on animals

1.1.5. Effects on man

1.1.6. Evaluation of health risks

1.2. Recommendations for further research
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, SAMPLING AND

ANALYSIS


2.1. Identity; physical and chemical properties

of asbestos minerals



2.1.1. Serpentine group minerals - chrysotile

2.1.2. Amphibole group minerals

2.1.2.1 Crocidolite (Riebeckite asbestos)

2.1.2.2 Amosite (Grunerite asbestos)

2.1.2.3 Anthophyllite asbestos

2.1.2.4 Tremolite and actinolite asbestos

2.2. Identity; physical and chemical properties

of other natural mineral fibres



2.2.1. Fibrous zeolites

2.2.2. Other fibrous silicates (attapulgite,

sepiolite, and wollastonite)



2.3. Sampling and analytical methods

2.3.1. Collection and preparation of samples

2.3.1.1 Air

2.3.1.2 Water

2.3.1.3 Biological tissues

2.3.1.4 Geological samples

2.3.2. Analysis

2.3.2.1 Light microscopy

2.3.2.2 Electron microscopy

2.3.2.3 Gravimetric determination



2.3.3. Other methods

2.3.4. Relationships between fibre, particle, and mass

concentration


3. SOURCES OF OCCUPATIONAL AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence

3.2. Man-made sources

3.2.1. Asbestos

3.2.1.1 Production

3.2.1.2 Mining and milling

3.2.1.3 Uses


3.2.2. Other natural mineral fibres

3.2.3. Manufacture of products containing asbestos

3.2.3.1 Asbestos-cement products

3.2.3.2 Vinyl asbestos floor tiles

3.2.3.3 Asbestos paper and felt

3.2.3.4 Friction materials (brake

linings and clutch facings)

3.2.3.5 Asbestos textiles

3.2.4. Use of products containing asbestos
4. TRANSPORT AND ENVIRONMENTAL FATE
4.1. Transport and distribution

4.1.1. Transport and distribution in air

4.1.2. Transport and distribution in water

4.2. Environmental transformation, interaction, and

degradation processes


5. ENVIRONMENTAL EXPOSURE LEVELS
5.1. Air

5.1.1. Occupational exposure

5.1.2. Para-occupational exposure

5.1.3. Ambient air

5.2. Levels in other media
6. DEPOSITION, TRANSLOCATION, AND CLEARANCE
6.1. Inhalation

6.1.1. Asbestos

6.1.1.1 Fibre deposition

6.1.1.2 Fibre clearance, retention,and translocation

6.1.2. Ferruginous bodies

6.1.3. Content of fibres in the respiratory tract

6.2. Ingestion
7. EFFECTS ON ANIMALS AND CELLS
7.1. Asbestos

7.1.1. Fibrogenicity

7.1.1.1 Inhalation

7.1.1.2 Intrapleural and intraperitoneal injection

7.1.1.3 Ingestion



7.1.2. Carcinogenicity

7.1.2.1 Inhalation

7.1.2.2 Intratracheal instillation

7.1.2.3 Direct administration into body cavities

7.1.2.4 Ingestion

7.1.3. In vitro studies

7.1.3.1 Haemolysis

7.1.3.2 Macrophages

7.1.3.3 Fibroblasts

7.1.3.4 Cell-lines and interaction with DNA

7.1.3.5 Mechanisms of fibrogenic and carcinogenic

action of asbestos
7.1.3.6 Factors modifying carcinogenicity

7.2. Other natural mineral fibres

7.2.1. Fibrous clays

7.2.1.1 Palygorskite (Attapulgite)

7.2.1.2 Sepiolite

7.2.2. Wollastonite

7.2.3. Fibrous zeolites - erionite

7.2.4. Assessment
8. EFFECTS ON MAN
8.1. Asbestos

8.1.1. Occupational exposure

8.1.1.1 Asbestosis

8.1.1.2 Pleural thickening, visceral, and parietal

8.1.1.3 Bronchial cancer

8.1.1.4 Mesothelioma

8.1.1.5 Other cancers

8.1.1.6 Effects on the immune system

8.1.2. Para-occupational exposure

8.1.2.1 Neighbourhood exposure

8.1.2.2 Household exposure

8.1.3. General population exposure

8.2. Other natural mineral fibres

8.2.1. Fibrous clays

8.2.1.1 Palygorskite (Attapulgite)

8.2.1.2 Sepiolite

8.2.2. Wollastonite

8.2.3. Fibrous zeolites - erionite
9. EVALUATION OF HEALTH RISKS FOR MAN FROM EXPOSURE TO ASBESTOS

AND OTHER NATURAL MINERAL FIBRES


9.1. Asbestos

9.1.1. General considerations

9.1.2. Qualitative approach

9.1.2.1 Occupational

9.1.2.2 Para-occupational exposure

9.1.2.3 General population exposure



9.1.3. Quantitative approach

9.1.3.1 Bronchial cancer

9.1.3.2 Mesothelioma

9.1.3.3 Risk assessment based on mesothelioma

incidence in women

9.1.4. Estimating the risk of gastrointestinal cancer

9.2. Other natural mineral fibres

9.3. Conclusions

9.3.1. Asbestos

9.3.1.1 Occupational risks

9.3.1.2 Para-occupational risks

9.3.1.3 General population risks



9.3.2. Other mineral fibres
10. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
10.1. IARC

10.2. CEC
REFERENCES

WHO TASK GROUP ON ASBESTOS AND OTHER NATURAL MINERAL FIBRES


Members
Dr I.M. Ferreira, Department of Preventive and Social Medicine,

Unicamp, Campinas, Brazil


Dr J.C. Gilson, Hembury Hill Farm, Honiton, Devon, United Kingdom

(Chairman)
Professor M. Ikeda, Department of Environmental Health, Tohoku

University School of Medicine, Sendai, Japan


Dr V. Kodat, Department of Hygiene and Epidemiology, Ministry of

Health of the Czech Socialist Republic, Prague, Vinohrady,

Czechoslovakia
Dr A.M. Langer, Environmental Sciences Laboratory, Mount Sinai

School of Medicine, New York, New York, USA


Dr F. Mansour, Amiantit, Saudi Arabia and Middle East, Damman,

Saudi Arabia


Ms M.E. Meek, Health and Welfare Canada, Health Protection Branch,

Environmental Health Centre, Tunney's Pasture, Ottawa, Ontario,

Canada (Rapporteur)
Ms C. Sonich-Mullin, US Environmental Protection Agency, ECAO,

Cincinnati, Ohio, USA


Dr U.G. Oleru, College of Medicine, University of Lagos, Lagos,

Nigeria (Vice-Chairman)


Professor K. Robock, Institute for Applied Fibrous Dust Research,

Neuss, Federal Republic of Germany


Members from Other Organizations
Dr A. Berlin, Commission of the European Communities, Luxembourg
Dr A.R. Kolff van Oosterwijk, Commission of European Communities,

Luxembourg


Observers
Dr K. Browne, Asbestos International Association, London, United

Kingdom


Dr E. Costa, Asbestos International Association (London), Genoa,

Italy
Dr J. Dunnigan, L'Institut de l'Amiante, Sherbrooke, Canada


Dr Fischer, Federal Health Office, Berlin (West)
Dr R. Konstanty, German Trade Union Congress, Düsseldorf, Federal

Republic of Germany


Mr L. Mazzuckelli, National Institute for Occupational Safety and

Health, Cincinnati, Ohio, USA


Dr E. Meyer, Federal Health Office, Institute for Hygiene of Water,

Soil, and Air, Berlin (West)


Dr H.-J. Nantke, Umweltbundesamt, Berlin (West)
Secretariat
Professor F. Valic, IPCS Consultant, World Health Organization,

Geneva, Switzerland (Secretary)a


Dr A. David, International Labour Office, Geneva, Switzerland
Mr A. Fletcher, International Agency for Research on Cancer, Lyons,

Franceb


Ms B. Goelzer, Office of Occupational Health, World Health

Organization, Geneva, Switzerland


Dr H. Muhle, Fraunhofer Institute for Toxicology and Aerosol

Research, Hanover, Federal Republic of Germany (Temporary



Adviser)

---------------------------------------------------------------------------



a Department of Public Health, Andrija Stampar School of

Public Health, University of Zagreb, Zagreb, Yugoslavia



b Present for only part of meeting.
NOTE TO READERS OF THE CRITERIA DOCUMENTS
Every effort has been made to present information in the

criteria documents as accurately as possible without unduly

delaying their publication. In the interest of all users of the

environmental health criteria documents, readers are kindly

requested to communicate any errors that may have occurred to the

Manager of the International Programme on Chemical Safety, World

Health Organization, Geneva, Switzerland, in order that they may be

included in corrigenda, which will appear in subsequent volumes.


ENVIRONMENTAL HEALTH CRITERIA FOR ASBESTOS AND OTHER NATURAL

MINERAL FIBRES


Following the recommendations of the United Nations Conference

on the Human Environment held in Stockholm in 1972, and in response

to a number of resolutions of the World Health Assembly and a

recommendation of the Governing Council of the United Nations

Environment Programme, a programme on the integrated assessment of

the health effects of environmental pollution was initiated in

1973. The programme, known as the WHO Environmental Health

Criteria Programme, has been implemented with the support of the

Environment Fund of the United Nations Environment Programme. In

1980, the Environmental Health Criteria Programme was incorporated

into the International Programme on Chemical Safety (IPCS), a joint

venture of the United Nations Environment Programme, the

International Labour Organisation, and the World Health

Organization. The Programme is responsible for the publication of

a series of criteria documents.
A WHO Task Group on Environmental Health Criteria for Asbestos

and Other Natural Mineral Fibres was held at the Fraunhofer

Institute for Toxicology and Aerosol Research, Hanover, Federal

Republic of Germany from 15-22 July 1985. Professor W. Stöber

opened the meeting and greeted the members on behalf of the host

institution, and Dr U. Schlottmann spoke on behalf of the

Government. Professor F. Valic addressed the meeting on behalf of

the three co-sponsoring organizations of the IPCS (WHO/ILO/UNEP).

The Task Group reviewed and revised the draft criteria document and

made an evaluation of the risks for human health from exposure to

asbestos and other natural mineral fibres.
The first draft of the document was a combination of texts

prepared by DR H. MUHLE and DR K. SPURNY of the Fraunhofer

Institute for Toxicology and Aerosol Research, Hanover, Federal

Republic of Germany, PROFESSOR F. POTT of the Medical Institute for

Environmental Hygiene, Düsseldorf, Federal Republic of Germany,

PROFESSOR J. PETO, of the Institute of Cancer, University of

London, London, United Kingdom, PROFESSOR M. LIPPMANN, of the

Institute of Environmental Medicine, New York University Medical

Center, New York, USA, MS M.E. MEEK, Department of National Health

and Welfare, Ottawa, Canada, and DR J.F. STARA and MS C. SONICH-

MULLIN, of the US Environmental Protection Agency, Cincinnati,

Ohio, USA.


A Working Group consisting of PROFESSOR C. McDONALD, MS M.E.

MEEK, DR H. MUHLE, MS J. HUGHES, and PROFESSOR F. VALIC reviewed

the first, and developed the second, draft.
The efforts of all who helped in the preparation and

finalization of the document are gratefully acknowledged.


1. SUMMARY AND RECOMMENDATIONS FOR FURTHER RESEARCH
1.1. Summary
1.1.1. Identity; physical and chemical properties, methods

of sampling and analysis
The commercial term asbestos refers to a group of fibrous

serpentine and amphibole minerals that have extraordinary tensile

strength, conduct heat poorly, and are relatively resistant to

chemical attack. The principal varieties of asbestos used in

commerce are chrysotile, a serpentine mineral, and crocidolite and

amosite, both of which are amphiboles. Anthophyllite, tremolite,

and actinolite asbestos are also amphiboles, but they are rare, and

the commercial exploitation of anthophyllite asbestos has been

discontinued. Other natural mineral fibres that are considered

potentially hazardous because of their physical and chemical

properties are erionite, wollastonite, attapulgite, and sepiolite.
Chrysotile fibres consist of aggregates of long, thin, flexible

fibrils that resemble scrolls or cylinders. The dimensions of

individual chrysotile fibres depend on the extent to which the

sample has been manipulated. Amphibole fibres generally tend to be

straight and splintery. Crocidolite fibrils are shorter with a

smaller diameter than other amphibole fibrils, but they are not as

narrow as fibrils of chrysotile. Amosite fibrils are larger in

diameter than those of both crocidolite and chrysotile. Respirable

fractions of asbestos dust vary according to fibre type and

manipulation.


Several methods involving optical phase contrast microscopy

have been developed for determining levels of asbestos fibres in

the air of work-places. Only fibres over 5 µm in length with an

aspect ratio > 3:1 and a diameter of less than 3 µm are counted.

Thus, the resulting fibre count can be regarded only as an index of

actual numbers of fibres present in the sample (fibres with

diameters less than the resolution of the light microscope are not

included in this assay). Fibres with diameters smaller than

approximately 0.25 µm cannot be seen by light microscopy, and an

electron microscope is necessary for counting and identifying these

fibres. Electron microscopes that are equipped with auxiliary

equipment can provide information on both structure and elemental

composition.
The results of analysis using light microscopy can be compared

with those using transmission or scanning electron microscopy, but

only if the same counting criteria are used.
1.1.2. Sources of occupational and environmental exposure
Asbestos is widely distributed in the earth's crust.

Chrysotile, which accounts for more than 95% of the world asbestos

trade, occurs in virtually all serpentine rocks. The remainder

consists of the amphiboles (amosite and crocidolite). Chrysotile

deposits are currently exploited in more than 40 countries; most of

these reserves are found in southern Africa, Canada, China, and the


USSR. There are, reportedly, thousands of commercial and

industrial applications of asbestos.


Dissemination of asbestos and other mineral fibres from natural

deposits may be a source of exposure for the general population.

Unfortunately, few quantitative data are available. Most of the

asbestos present in the atmosphere and ambient water probably

results from the mining, milling, and manufacture of asbestos or

from the deterioration or breakage of asbestos-containing

materials.
1.1.3. Environmental levels and exposures
Asbestos is ubiquitous in the environment because of its

extensive industrial use and the dissemination of fibres from

natural sources. Available data using currently-accepted methods

of sampling and analysis indicate that fibre levels (fibres > 5 µm

in length) at remote rural locations are generally below the

detection limit (less than 1 fibre/litre), while those in urban air

range from < 1 to 10 fibres/litre or occasionally higher.

Airborne levels in residential areas in the vicinity of industrial

sources have been found to be within the range of those in urban

areas or occasionally slightly higher. Non-occupational indoor

levels are generally within the range found in the ambient air.

Occupational exposure levels vary depending on the effectiveness of

dust-control measures; they may be up to several hundred fibres/ml

in industry or mines without or with poor dust control, but are

generally well below 2 fibres/ml in modern industry.
Reported concentrations in drinking-water range up to 200 x 106

fibres/litre (all fibre lengths).


1.1.4. Toxicological effects on animals
Fibrosis in many animal species, and bronchial carcinomas and

pleural mesotheliomas in the rat, have been observed following

inhalation of both chrysotile and amphibole asbestos. In these

studies, there were no consistent increases in tumour incidence at

other sites, and there is no convincing evidence that ingested

asbestos is carcinogenic in animals. Data from the inhalation

studies have shown that shorter asbestos fibres are less fibrogenic

and carcinogenic.


Few data are available concerning the pathogenicity of the

other natural mineral fibres. Fibrosis in rats has been observed

following inhalation of attapulgite and sepiolite; a remarkably

high incidence of mesotheliomas occurred in rats following

inhalation of erionite. Long-fibred attapulgite induced

mesotheliomas following intrapleural and intraperitoneal

administration. Wollastonite also induced mesothelioma after

intrapleural administration. Erionite induced extremely high

incidences of mesotheliomas following inhalation exposure and

intrapleural and intraperitoneal administration.


The length, diameter, and chemical composition of fibres are

important determinants of their deposition, clearance, and

translocation within the body. Available data also indicate that

the potential of fibres to induce mesotheliomas following

intrapleural or intraperitoneal injection in animal species is

mainly a function of fibre length and diameter; in general, fibres

with maximum carcinogenic potency have been reported to be longer

than 8 µm and less than 1.5 µm in diameter.


1.1.5. Effects on man
Epidemiological studies, mainly on occupational groups, have

established that all types of asbestos fibres are associated with

diffuse pulmonary fibrosis (asbestosis), bronchial carcinoma, and

primary malignant tumours of the pleura and peritoneum

(mesothelioma). That asbestos causes cancers at other sites is

less well established. Gastrointestinal and laryngeal cancer are

possible, but the causal relationship with asbestos exposure has

not yet been firmly established; there is no substantial supporting

evidence for cancer at other sites. Asbestos exposure may cause

visceral and parietal pleural changes.


Cigarette smoking increases the asbestosis mortality and the

risk of lung cancer in persons exposed to asbestos but not the risk




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