9 Questions and Answers on Chrysotile and Health

Environmental Asbestos Exposure Levels & Materials

Question 1 Biological Potency
Is there evidence for a difference in biological potency between chrysotile asbestos and the amphibole fibres types?

Answer to Question 1
Yes, there is an overwhelming body of evidence, based on
epidemiological studies on clinical findings, and on lung tissue
mineral analysis in humans showing a definite difference in potency
between chrysotile and the amphiboles.

Recently published data show that:

1. The morbidity and mortality experience of workers handling
chrysotile only is much less severe than that of workers exposed to
amphiboles (or to mixtures containing them).

2. The results of mineral contents of lung tissue by fibre type show
that large amounts (100-fold) of amphiboles are found in the lungs of
cases compared to controls. This is not so for chrysotile.

References for Question 1

Wagner JC, Moncrieff CF, Coles R, Griffiths DM and Munday, DE (1986). British Journal of Industrial Medicine 43:391-395

A study among naval dockyard workers showing increasing amounts of
amphiboles in lung tissue and increasing severity of asbestosis, but no
increase of chrysotile.

Wagner JC, Newhouse ML, Corrin B, Rossiter CER and Griffiths DM (1988). British Journal of Industrial Medicine 45(5):301-308

The lungs from 36 past workers of an asbestos factory using
chrysotile, crocidolite and amosite were examined. Crocidolite and
amosite lung contents were strongly associated with asbestosis and with
mesothelioma, whereas no such correlation was evident with chrysotile
and mullite.

Albin A, Pooley FD, Stromberg U, Attewell R, Mitha R and Welinder H (1994).
Occup. Environ. Med. 51: 205-211

Retention patterns of asbestos fibres in lung tissue among asbestos
cement workers. A study showing different kinetics for amphibole and
chrysotile fibres in human lung tissue. Amphibole fibre concentrations
increase with duration of exposure, whereas chrysotile concentrations
do not. The authors indicate that their study supports a former finding
of a possible adaptive clearance of chrysotile and conclude that their
findings support the hypothesis that adverse effects are associated
rather with the fibres that are retained (amphiboles), than with the
ones being cleared (largely chrysotile).

McConnell EE, Chevalier HJ, Hesterberg TW, Hadley JG, Mast RW
(1994). ILSI Monograph - Toxic and Carcinogenic Effects of Solid
Particles in the Respiratory Tract. Eds. DL Dungworth, JL Mauderly and
G. Oberdorster. ILSI Press, Washington, DC (pp. 461-467)

Following an inhalation study where the effects of crocidolite and
chrysotile were compared, the authors conclude: crocidolite causes more
inflammatory disease and at an earlier time than chrysotile asbestos.

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Question 2 Fibre Length

Is there evidence for a difference in potency of fibres according to fibre length?

Answer to Question 2
Two different sets of data are pertinent to this question:

There is evidence from experimental studies that while long (thin
and durable) fibres are associated with ill-health effects in animals,
no such association is found with asbestos fibres shorter than ~ 5
microns. The great majority of fibres found in the general environment
are shorter than 5 microns. Thus, while the presence of long fibres,
such as may be found in the workplace, may be associated with
ill-health effects in workers, the presence of short asbestos fibres in
the general environment should not be of concern, at least for
chrysotile asbestos.

References to Question 2

Doll R, (1989). In Non-Occupational Exposure to Mineral Fibres, Eds. J. Bignon, J. Peto and R. Saracci.
WHO/IARC Scientific Publications No. 90, Lyon: 511-518.

“Properly speaking, no particle should be described as a fibre
unless it is at least 5 µm long and the diameter is less than one third
of its length”

“There is increasing evidence that short fibres (properly described
as elongated particles) are much less carcinogenic, if they are
carcinogenic at all”.

Davis JMG, Addison, J, Bolton RE, Donaldson K, Jones AD, and Smith T (1986).
British Journal of Experimental Pathology 67(3): 415-430.

The effects of long vs short (100% shorter than 5µ) amosite fibres
were compared. At the end of 12 months of dust inhalation (10 mg/m„)
long fibres caused development of widespread pulmonary fibrosis, and a
third of the animals developed pulmonary tumours or mesotheliomas. No
fibrosis at
all, and no pulmonary neoplasms were found in animals treated with short fibre dust.

Chatfield EJ (1983). Short mineral fibres in airborne dust.
Proceedings from a Symposium, Stockholm, September 28, 1982, Government
of Sweden, Arbete och Halsa (publisher) 19: 9-93.

In rural areas the level of asbestos fibres longer than 5 microns
are less than 1 fibre/litre (0.001 f/cc). In urban environments higher
levels, up to 40 f/l (0.04 f/cc) were observed. Most fibres in general
atmosphere are shorter than 5 microns (95-98%).

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Question 3 Asbestos Concentration Levels
What is the risk associated with the presence of asbestos at concentration levels found in the general environmental air?

Answer to Question 3
Asbestos fibres in the general environmental air have been present long
before manís exploitation of the mineral. This phenomenon is due to the
natural erosion from geological formations quite common throughout the
world, and the total amount of asbestos emitted from natural sources is
much greater than that emitted from industrial sources.

In general, the ambient air concentrations rarely exceed 0.001 f/cc.

At these low levels, the risk is undetectably low, indeed much lower
than other risks, such as natural background radiation. Such a low risk
has been labelled: “acceptable” by the WHO, or “not significant”, by
the Ontario Royal Commission on Asbestos or “further control not
justified”, by the Royal Society, London.

References to Question 3

Churg A (1986). American Review of Respiratory Disease, 134 (1):125-127.

Study comparing health effects in residents of chrysotile mining
towns, where levels are from 200 to 500 times higher than in most North
American cities, to those seen in urban residents. In spite of higher
levels in these mining towns, no evidence of higher asbestos-related
diseases were found. The author concludes: “These observations should
provide reassurance that exposure to chrysotile asbestos from urban air
or in public buildings will not produce detectable disease”.

This is in agreement with other reports on residents of chrysotile
mining towns in Québec, which have consistently failed to demonstrate
excess respiratory disease incidence. These are:

McDonald AD, and McDonald JC (1980). Cancer 46(7): 1650-1656.

Siemiatycki J. (1982). Health effects on the general population
(mortality in the general population in asbestos mining areas).
Proceedings, World Symposium on Asbestos, Montreal, 25-27 May,
pp.337-348.

Pampalon R, Siemiatycki J, et Blanchet M, (1982). Pollution
environnementale par l'amiante et santé publique au Québec. Union
Médicale du Canada 111(5): 475-489.

McDonald JC, (1985). Health implications of environmental exposure to asbestos. Environmental Health Perspectives 62:319-328.

Report of the Royal Commission on Matters of Health and Safety
Arising from the Use of Asbestos in Ontario (1984). Eds. JS Dupré, JF
Mustard, RJ Uffen. Published by the Ontario Ministry of the Attorney
General 2:666.

“Considering all of the above data together, we conclude that
asbestos fibre concentrations in the ambient air are extremely low.
Counts of fibres longer than 5 microns taken by electron microscope are
often less than 0.001 f/cc. If we consider the fibres that would be
seen by an optical microscope, it is extremely rate in Ontario to have
concentrations greater than 0.001 f/cc. The recent Ontario data suggest
that fibre levels are lowest where population density is lowest,
although the earlier Ontario data did not reveal this relationship. In
Chapter 9 we conclude that the health risks presented to building
occupants from exposure to 0.001 optically visible fibres per cubic
centimetre is not significant. It follows that the fibre levels
discussed in this section present a clearly insignificant health risk.
We see no reason to worry about the health effects of the prevalent
level of asbestos fibres in the outdoor air in Ontario”.

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Question 4 Controlled Exposure Levels
Asbestos in the workplace: Can asbestos be handled without
undue risk to the workers? What is the risk to workers handling
chrysotile asbestos at today's controlled exposure levels?

Answers to Question 4
Lung fibrosis, lung cancer and mesothelioma have been definitely
correlated with exposure to airborne respirable fibres of asbestos.
This correlation has been ascertained for both intensity (dose) and
duration of exposure. The correlation is especially strong for
mesothelioma and exposure to the amphibole varieties of asbestos.

With regard to intensity (or exposure levels) of exposure, this
aspect has been examined more recently, especially with regard to the
very low exposure levels to chrysotile only.

Results of recently reported cohorts surveys, where the health
experience at very low exposure levels to chrysotile only was examined,
support the following statements:

There are low levels of exposure to chrysotile asbestos in the
workplace, where no excess morbidity (disease) and mortality have been
detected. There is no undue risk to workers handling chrysotile
asbestos, at today's controlled exposure levels (~ 1 f/cc).

References for Question 4

Berry G, and Newhouse ML (1983). British Journal of Industrial Medicine 40(1):1-7

A mortality (1942-1980) study carried out in a factory producing
friction materials, using almost exclusively chrysotile. Compared with
national death rates, there were no detectable excess deaths due to
lung cancer, gastrointestinal cancer, or other cancers. The exposure
levels were low, with only 5% of men accumulating 100 fibre-years/ml.
The authors state: “The experience at this factory over a 40-year
period showed that chrysotile asbestos was processed with no detectable
excess mortality”.

Newhouse ML, and Sullivan KR (1989). British Journal of Industrial Medicine 46(3):176-179.

The 1983 study (referred to above), has been extended by seven
years. The authors confirm that there was no excess of deaths from lung
cancer or other asbestos related tumours, or from chronic respiratory
disease. After 1950, hygienic control was progressively improved at
this factory, and from 1970, levels of asbestos have not exceeded 0.5-
1.0 f/ml. The authors conclude: “It is concluded that with good
environmental control, chrysotile asbestos may be used in manufacture
without causing excess mortality”.

Thomas HF, Benjamin IT, Elwood PC, and Sweetnam PM (1982). British Journal of Industrial Medicine
39(3): 273-276.

In an asbestos-cement factory using chrysotile only, 1,970 workers
were traced, and their mortality experience was examined. There was no
appreciably raised standardized mortality ration (SMR) for the causes
of death investigated, including all causes, all neoplasms, cancer of
the lung and pleura, and cancers of the gastrointestinal tract. The
authors indicate: “Thus the general results of this mortality survey
suggest that the population of the chrysotile asbestos-cement factory
studied are not at any excess risk in terms of total mortality, all
cancer mortality, cancers of the lung and the bronchus, or
gastrointestinal cancers”.

McDonald JC, Liddell DK, Dufresne A, and McDonald AD (1993). British Journal of Industrial Medicine
50:1073-1081.

This study is undoubtedly the largest cohort of asbestos workers
ever studied and followed for the longest period is that of the miners
and millers of the chrysotile mines in Québec. The cohort, which was
established in 1966, comprises some 11,000 workers born between
1891-1920 and has been followed ever since. Optimal use was made of all
available dust measurements to evaluate for each cohort member his
exposure in terms of duration, intensity and timing. Findings on
mortality have been published on five occasions, and the most recent
report provides an update of the results of analysis of mortality for
the period 1976-1988 inclusive.
One of the central findings of this update is that over several narrow
categories of exposure up to 300 mpcf.y, the SMRs for lung cancer
fluctuated around unity, with no evidence of trend and increased steeply
above that exposure level. Still more recently, the same authors
confirmed their original findings with a mortality update up to 1992:
Liddell FDK, McDonald AD and McDonald JC. Ann. Occup. Hyg. 41:13-35
(1997).

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Question 5 Single Asbestos Fibres
Can exposure to one single asbestos fibre kill?

Answers to Question 5
It should be realized that it is almost physically impossible to test
this proposition experimentally. It is virtually impossible to
challenge cells, tissues or whole animals to one single fibre, because
of the ubiquity of asbestos fibres; it should be realized that one
milligram of asbestos may contain several hundred million respirable
fibres. Furthermore, it is a universally acknowledged fact that
experimental protocols call for a minimum dose of several hundreds of
thousands of fibres in order to induce observable effects.

On the other hand, the following facts may help in reaching sensible judgement:

1. Every 60 seconds, the lungs of a normal person handle some 10 liters of air.

2. In the general environmental air of cities and rural areas,
concentrations of approximately l fibre per liter (possibly a little
more or a little less, depending on circumstances of location, weather
conditions, etc.) are found around the world.

3. It follows from these two observations that every day, 14,400
liters of air (10 liters x 60 min. x 24 hrs), each one containing 1
fibre, transit through the lungs of a “normal” non-occupationally
exposed person.

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Question 6 Asbestos in Water
Asbestos in Water: Does the use of asbestos-cement pipes
contribute significantly to the presence of asbestos in water? Is there
a risk associated with the presence of asbestos in drinking water?

Answers to Question 6
The use of asbestos-cement (A/C) pipes dates back to the early 1920's,
and it is estimated that by the end of the 1980ís, close to 3 million
kilometres of pipes will have been laid worldwide to convey potable
water.

Highly aggressive waters may attack the cement matrix, and
consequently lead to the release of fibres into the water circulating
through the pipes, and A/C pipes are not recommended for use under such
highly corrosive conditions, unless protected with specially designed
internal protective lining.

The results of most studies published so far indicate that the
source waters already contain asbestos fibres (mostly shorter than 1 u
in length) before passing through the A/C pipe systems, often in
numbers reaching several millions per liter, and it is generally agreed
that A/C pipes do not appreciably raise the asbestos fibre content of
water, and that the quantities found are within those which occur
naturally.

As to the risk of health resulting from the presence of asbestos in
potable water, results of several years of laboratory investigation in
animals fed for their entire lifespan with very large (several billions
of fibres every day) quantities of asbestos incorporated into their
diet have consistently failed to indicate any raised incidence of
gastrointestinal tumours, or of any other pathological changes in the
gastrointestinal tract.

Epidemiological studies on human health effects related to asbestos
levels in drinking water have failed to indicate any increased risk of
alimentary tract tumours following the direct ingestion of asbestos
fibres.

References for Question 6

Hallenbeck WH, Chen EH, Hesse CS, Patel-Mandlik K, and Wolff AH
(1978). Journal of American Water Works Association. 70(2):97-102

A study of 15 water supply systems in the State of Illinois (U.S.A.)
where some asbestos cement pipes were up to 50 years old, and where the
water was non-aggressive to moderately aggressive, showing no
significant differences before and after passing through the
asbestos-cement pipe network.

MacRae KD (1988). Journal of the Royal College of Physicians of London 22(1):7-10

In this review article, the author concludes: “It would thus seem
highly unlikely that the asbestos-cement pipe distribution system makes
any biologically significant contribution to the asbestos content of
water passing through it”. “It is highly improbable that asbestos
release from asbestos cement pipes is relevant to the development of
cancer.”

Millette JR, Craun GF, Stober JA, Kraemer DF, Tousignant HG, Hidalgo E,
Duboise RL, and Benedict J (1983. Environmental Health Perspectives.
53:91-98

Some areas in Florida have been receiving drinking water through
asbestos-cement pipes for 30-40 years. The authors mention: “No
evidence for an association between the use of A/C pipes for carrying
drinking water and deaths due to gastrointestinal and related cancers
was found in this study”.

Polissar L, Severson RK, Boatman ES and Thomas DB (1982). American Journal of Epidemiology 116(2):314-328

The site of the study was Puget Sound region of Western Washington,
and the state's three largest metropolitan areas (Everett, Seattle and
Tacoma) were used for comparison. Everett was the “high exposure
municipality”, where asbestos levels ranged from 37.2 to 556 million
fibres per liter. Seattle and Tacoma had relatively low concentrations,
averaging 7.3 million fibres per liter. The three metropolitan areas
were subdivided into census tracts grouped by asbestos concentration.
Data on cancer incidence were obtained from a surveillance registry;
cancer mortality information came from death certificates. Duration of
exposure to asbestos in drinking water was estimated and divided into
long term (greater than 30 years) versus short term (less than 30
years) groups. Following the analysis of the results, the principal
investigator, Dr Lincoln Pollisar of the Fred Hutchinson Cancer
Research Center, concluded that: “Results of this study and prior
studies of cancer in relation to waterborne asbestos are inconsistent,
and provide little evidence that asbestos in community water supplies
has altered the risk of any cancer”.

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Question 7 Asbestos Substitutes
Asbestos substitutes: Non-asbestos fibrous materials are used
extensively, and are often proposed as substitutes for asbestos. In
which areas of application are these materials used? Is there evidence
available indicating biological activity of non-asbestos fibrous
materials?

Answers to Question 7
Non-Asbestos fibrous materials, both man-made and extracted from
natural deposits, are used and/or proposed as substitutes for asbestos.
In industrialized countries, they can be found in practically all the
major areas of applications of asbestos.

There are wide variations in competitiveness according to price,
availability,technical performance, ease of handling and mixing,
compatibility with other materials in composites, durability, etc.

There is no single fibrous alternative that could replace asbestos
in all of its many varied applications. On the other hand, some fibrous
materials are really not alternatives for asbestos, as they are used in
areas where asbestos cannot be used (example: very high temperature
refractory materials).

Compared to asbestos, evidence of biological activity of
non-asbestos fibrous materials has been reported only recently. Except
for a very limited number of materials (example: mineral wools),
epidemiological scrutiny has yet to be undertaken in order to
substantiate possible human health hazards.

On the other hand, recently published results from cell, tissue and
animal experimentation indicate that all the materials reviewed in this
section display some degree of biological activity.

These results suggest that their widespread production and use
should be governed by appropriate monitoring and control of dust
exposure, especially so for materials which are long and thin and which
display long “in vivo” durability.

References for Question 7

U.S. Dept. Of Labor (OSHA) Synthetic Mineral Fibers: Hazard Description:

The American Occupational Safety and Health Administration (OSHA)
has declared that glass fibres are “reasonably anticipated to be a
carcinogen”. The OSHA report states that “Several epidemiological
studies have demonstrated statistically significant elevations in the
risk of lung cancer and other respiratory system cancers among workers
employed in fibrous glass and mineral wool manufacturing facilities”.

International Agency for Research on Cancer (IARC) 1988. Man-Made
Mineral Fibers: In IARC Monographs on the Evaluation of the
Carcinogenic Risk of Chemicals to Man, 43:39-171, Lyon, France, WHO.

The WHO's IARC has classified glasswool, rockwool, slagwool and refractory ceramic fibres as “possibly carcinogenic to humans.”

INSERM (French medical research council) Expert Council, Health effects
of Substitute Fibres, Paris, June 1998: Quote from the Executive
Summary:

Given the present uncertainties concerning the effects of asbestos
substitute fibres in humans, it is important to ensure that exposure
levels in users of products containing asbestos substitute fibres are
as low as possible.

Looking at the conclusions of the various chapters in the report,
questions recur about the possibility of risk involving rock wool and
ceramic fibres in particular.

Once again, there is little or no sound toxicological data for
materials such as cellulose (whose proinflammatory nature is known) and
polyvinyl alcohol fibres which are in widespread use today.

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Question 8 Asbestos Friction Materials
Asbestos friction materials: What is the contribution to the
general environment resulting from the use of asbestos in friction
materials?

Answers to Question 8
Asbestos has been a major constituent of automotive friction materials
for more than 70 years, where the presence of mostly chrysotile
asbestos (from 25% to 65% by weight) imparts strength, flexibility,
heat resistance to brake linings, in addition to friction and wear
properties.

Comprehensive investigations conducted with the support of the U.S.
EPA have shown that on the average, more than 99.7% of the asbestos
emitted as a result of wear and abrasion has been converted into other
products such as forsterite, a material which has been found
non-carcinogenic in animals. Furthermore, it has been determined that
such asbestos (less than 1%) as may be present in wear debris consists
predominantly of very short (0.3 µ) fibres.

Thus, the emission of free fibres resulting from brake lining wear
is a negligible health factor in urban air pollution. Indeed, recent
estimates of air concentrations of asbestos resulting from vehicular
brakes in large U.S. cities range from 0.051 ng/m³ (Rochester, NY) to
0.258 ng/m³ (Los Angeles, CA). If a conversion factor of 30 fibres
measured optically per nanogram of asbestos used, the values for Los
Angeles would be 7.74f/M³ or 0.000007 f/cc.

References for Question 8

Lynch JR (1968). Journal of the Air Pollution Control Association. 18(12): 824-826

This study by investigators of the U.S. Department of Health,
Education and Welfare, Public Health Service (Cincinnati) provides
evidence from analysis of dust obtained from inside brake drums removed
for brake relining, and also from laboratory experiments devised to
permit sampling decomposition products of the lining under operating
conditions. The authors conclude: “Only a very small proportion of the
asbestos worn from brake linings is released as free fibre; the
remainder is converted into some other mineral as a result of the
extreme temperatures generated at small spots on the lining surface.
Thus, although urban air contains a few free fibres as a result of
brake lining wear, they represent a very small proportion of the total
asbestos used in the manufacture of brakes”.

Jacko MG, DuCharme RT, and Somers JH (1973). Society of Automotive Engineers, Reprint # 730548: 1813-1831

In this report by scientists from the Bendix Corporation and the
U.S. EPA, the authors state that on the average, more than 99.7% of the
asbestos during vehicle operation is trapped or emitted as olivine or
forsterite particles.

Jaffrey S (1990). Annals of Occupational Health. 34: 529-534

Data in the U.K. have been obtained from situations of highly
intensive vehicular traffic (City of London), indicating that the use
of asbestos in such applications causes no measurable contribution to
urban environmental asbestos air concentrations. The asbestos fibre
counts presumably released from vehicular traffic at two very busy road
junctions in the Greater London Area (Motorway #1 - North Circular Road
and Euston Underpass) were from 0.0002 to 0.0004 f/ml.

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Question 9 Fibre-Cement construction materials
Fibre-Cement construction materials: What is the contribution
to the environment resulting from the use of chrysotile in fibre cement
materials?

Answers to Question 9
Chrysotile cement was invented in Austria in 1901 and has been
widely used every since worldwide. By mixing chrysotile fibre with
cement, this chemical and physical links allows the manufacture of a
lighter and
stronger slate. Thus, this strong link between the fibre and the matrix
does not allow the fibre to become airborne, even in areas of heavy
water and wind erosion.

Studies undertaken in areas where chrysotile cement materials are
widely used show that their contribution to the presence of chrysotile
fibres in the environment is not significant.

References to Question 9

Teichert U (1986). Staub Reinhaltung der Luft. 46:432-434

Data pertinent to the extent of possible emissions from A/C
construction products and the air concentrations in various countries
have been obtained at different times from 1980 to 1997.

In Germany, the study of emission on coated and uncoated and coated
roofing materials revealed low asbestos fibre concentrations, even
though severe corrosion was observed on uncoated asbestos cement roofs and a considerable quantity of materials containing
asbestos could be removed by blowing and suction. Yet, asbestos fibre
concentrations that were measured in populated areas were well below
the level considered acceptable by German health authorities, i.e.:
clearly below 1000 fibres per cubic metre.

Felbermayer W, and Ussar MB (1980). Research Report: Airborne
asbestos fibres eroded from asbestos cement sheets. Institute fur
Umweltschutz and Emissionsfragen, Leoben, Austria

In Austria, a comparison of the asbestos fibre concentrations in
those areas with and without asbestos cement roofing (< 0.0001 f/ml)
led to the conclusion that there is no statistically significant
connection between the use of asbestos cement materials and the
asbestos fibre concentrations found in the various measurement areas.

Safety & Welfare of Western Australia (1990). Report of the Working Party on Asbestos Cement Products

In Australia, possible contribution from asbestos cement roofing
materials of school buildings to the air concentrations in the vicinity
of these buildings was studied. It was found that measurements were
mostly < 0.0002 f/ml.

From the chrysotile.com web site:
www.chrysotile.com

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