Substitutes
Chrysotile-free but not risk-free!
A simple equation has been circulating for a long time: asbestos-free = risk-free. Conventional wisdom was that all one had to do was replace asbestos fibres with other fibres, and the job was done. Industries and governments therefore avoided using asbestos in many products in favour of untested substitute fibres.
Toxicity and regulation of substitute fibres
Replacing chrysotile is a very complex operation. Evaluations of the risks and hazards of a good many other fibres are now clear enough that legislators are beginning to impose regulations to control these substitutes.
In 1993, a group of experts brought together by the World Health Organization (WHO) issued Environmental Health Criteria 151, stating that all respirable and biopersistent fibres must be tested to check their toxicity and carcinogenicity. In fact, recent studies have shown that many fibres used to replace asbestos in numerous products may be as hazardous or even more hazardous than chrysotile asbestos: this is notably the case for fibreglass, rock wools, refractory ceramic fibres and aramid fibres. In 1993, the International Program on Chemical Safety (IPCS) explicitly recommended that exposure to any respirable and durable fibre be controlled to the same extent as that required for asbestos until the data prove that lesser controls would be sufficient.
Germany classifies glass wools, rock wools and mineral wools as probable carcinogens. Several other countries are also moving in this direction and have introduced exposure standards and work methods for several fibres. However, to protect workers health effectively, any such regulation should encompass all fibres. In 1994, the European Commission announced a complete fibre review program, which should make it possible to establish a new classification based on carcinogenicity. Please see the chart of substitutes for a summary of scientific findings on the health effects of the main categories of substitute fibres.
Reliability and performance of substitute fibres in brakes
In addition to the health problems linked to their handling, many non-asbestos friction materials may have inferior physical and technical characteristics. Despite higher manufacturing costs than chrysotile-containing products, and despite years of technological research and development, substitute fibre-based friction products still pose performance problems for certain types of vehicles.
In the United States, every year exploding brake drums on heavy trucks cause numerous highway fatalities. Diagnoses of truck brake drums in the past few years show that the rupture is often linked to a defective non-asbestos brake shoe. In addition, a study by the EPA and the American Society for Mechanical Engineers shows that it is dangerous to install non-asbestos brake linings on cars initially designed with linings containing asbestos.
To alleviate the problems of unbalanced non-asbestos brakes, manufacturers have developed anti-locking systems. It is still too soon to evaluate the advantages and risks of these products, but one thing is clear, the price of cars has been increased... without necessarily adding to the safety of consumers.
Replacement of chrysotile in gaskets
It takes 50 to 60 different substances to replace the various grades of chrysotile fibre used in the gasket industry. Development of these substances and their industrial applications involves very costly research for the industry, and hence, increased costs to consumers. Such a composition may result in sudden rupture and shattering of the gasket, particularly in high temperature, high pressure applications. In addition, it requires more frequent inspections than those usually foreseen for chrysotile-based gaskets which were much more resistant.
Chart of substitutes
Substitutes not without risks
Download this chart (.pdf 36kb)
| Substance |
Health effects |
Conclusions |
| Fibreglass |
increased incidence of lung cancers in glass wool production workers (3)
listed by the U.S. as "a substance which may reasonably be anticipated to be a carcinogen" (4)
listed by German MAK Commission as "a substance to be treated as if a probable cause of cancer"
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"Our review then examines the carcinogenic potency of glass fibers to humans in comparison with asbestos fibers and concludes that on a fiber-per-fiber basis, glass fibers may be as potent or even more potent than asbestos." (Infante et al., Am. J. Ind. Med., 1994) |
| Silicon carbide whiskers |
|
"Silicon carbide whiskers have the potential, at least, to cause significant immediate and long-term pulmonary damage. It appears to be more toxic than crocidolite." (Vaughan et al., Env. Res., 1993) |
| Glass and rock wool |
IARC Class 3 “not classifiable as to carcinogenicity from humans”
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| Aramid fibre |
has caused fibrosis and lung tumours in inhalation exposure studies on rats (1)
"exposures to these fibres should be controlled to the same degree as that required for asbestos until data supporting a lesser degree of control become available." (2)
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"Results of cytotoxicity tests indicated that Aramid was as toxic to hamster trachael epithelial cells and rat lung fibroblast cells as were crocidolite and chrysotile asbestos when expressed on both an equal mass and equal fiber number basis." (Marsh et al., Drug and Chem. Toxic., 1994) |
| All respirable and durable fibres |
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"Exposures to these fibres should be controlled to the same degree as that required for asbestos until data supporting a lesser degree of control become available." (IPCS, 1993) |
| Refractory ceramic fibre (RCF) |
evidence of fibrogenicity and carcinogenicity in animal implantation and inhalation studies (5)
IARC Class 2B "possibly carcinogenic to man"
listed by German MAK Commission as "a substance with known carcinogenic potential in humans"
listed by the U.S. as a "probable human carcinogen"
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"Both rats and hamsters exhibited dose-dependent increases in proliferation of pleural mesothelial cells following exposure to both fibre types (MMVF et RCF-1)." (Rutten et al., Fund Appl. Tox., 1994) |
| Magnesium sulfate fibre, calcium sulfate fibre and fibreglass |
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"it is suggested that some of man-made fibers have a greater ability than asbestos to induce tumor." (Adachi et al., Environ. Research, 1991) |
| Carbon / graphite fibre |
evidence of lung function deterioration in workers (1)
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| Phosphate fibre |
intrapleural implantation in rats can induce fibrosarcomas (4)
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| Attapulgite |
causes mesothelioma in experimental animals (7)
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| Wollastonite |
evidence of lung fibrosis, pleural thickening and chronic bronchitis in humans (6)
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(1) ILO Safety in the use of mineral and sythetic fibres, 1989, p. 40
(2) IPCS Environmental Health Criteria 151, Selected Synthetic Organic Fibres, WHO, l993
(3) Saracci, R. et al.(1984) Brit J Ind Med. 41:425-436
(4) U.S. EPA, Status Report FTI-OTS-0386-0486, (1986)
(5) Davis, JMG et al.(1983), Biological effects of man-made mineral fibres, Euro Reports and Studies: 81:p. 124
(6) Huuskonen, M.S. et al.(1983) Environ. Res. 30:291-304
(7) Pott, F. et al.(1976) Ann. Anat. Pathol. 21:237-246
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