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.