It was thought that it would be enough to replace chrysotile fibres with other fibres. To polish their image and avoid responsibility for their past activities, some manufacturers decided to cease using chrysotile in as many products as possible, while using substitutes that had not always been scientifically tested either for technical or medical problems.
Replacing chrysotile is a very complex operation. The risks and dangers with many other fibres are sufficiently clear now that some legislators are starting to impose regulatory constraints on these substitutes. The regulatory authorities are invited to apply the standards for chrysotile to all industrial fibres if they truly want to protect the health and safety of workers.
Since the main argument used to substitute chrysotile is based on the premise that its use presents a potential health risk, it is essential to ensure that the replacement products are harmless or less harmful, as indicated in Convention 162 from the ILO.
Since 1993, a group of experts convened by the WHO, stated in Environmental Health Criteria 151, that all respirable and biopersistent fibres must be tested for their toxicity and carcinogenicity. In fact, recent studies show that many of the fibres used to replace asbestos in many products are not without potential risk. These are primarily glass fibre, rock wool, refractory ceramic fibres, aramid fibres and cellulose fibres. The same year, the International Program on Chemical Safety (IPCS) clearly recommended that “exposure to any breathable and durable fibre should be controlled in the same way as asbestos until such time as it is proven that less stringent controls would be sufficient."
We understand that Germany classifies glass wool, rock wool and slag wool substrates as carcinogenic products. Several other countries have also taken the same approach and have adopted standards for exposure and work methods for several fibres. However, the fact remains that to effectively protect the health of workers regulations should apply to all fibres. The European Commission further announced, in 1994, a complete study program on fibres that should make it possible to establish a new classification according to their carcinogenicity.
The scientific community agrees that in too many cases, there is no valid scientific evidence that supports the assumption that substitutes are safe. Even the “Institut National de la Santé et de la Recherche Médicale (INSERM)” in France, recognizes that the scientific data is insufficient on substitute products to make a decision regarding their harmfulness. More recently, the WHO reached the same conclusion in its publication “WHO Workshop on Mechanisms of Fibre Carcinogenesis and Assessment of Chrysotile Asbestos Substitutes.”
When the Court of Appeals of the United States reversed, in 1991, the asbestos ban and phase-out rule proposed by the EPA, it did stress that national legislators should consider the cost of introducing measures to ban a product. It also stressed that substitute products for products that contain asbestos also present potential risks to human health that could be more serious than potential risks from asbestos.
This is also a rising concern among workers and regulatory agencies. The ILO adopted a Code of Practice for the use of Synthetic Fibres, which recommends the same precautionary measures as with chrysotile. This comes as no surprise as manipulating, mixing, cutting and unprecautionary handling of all fibrous materials can generate dust. In the case of chrysotile, international references are available for determining, what is a reasonable limit of dust exposure not to exceed. This is unfortunately not always the case for most substitute fibres.
The prohibition of asbestos would mean substituting a known and adequately regulated product with others that are unknown and often not regulated. Several of these products have similar effects on health without the benefits of chrysotile. For example, recent studies show that certain types of fibres and products used to replace chrysotile are more biopersistent than chrysotile.
Because the use of substitute fibres to asbestos is relatively recent, not enough epidemiology studies are presently available that evaluates their human health effects. With the negative publicity arising from the past uses of asbestos fibres, these new fibres were developed to take over a growing market, encouraged by political stance (like in the European Union) supporting their use. Many scientists have raised serious concerns about possible health effects of these new materials and especially about the fact that the reliable scientific information is very meagre or non-existent. Today, it has become abundantly clear that “biopersistence” is one key parameter to take into account when comparing the toxicity of respirable fibres.
It has been confirmed by numerous scientists, in several studies, that respirable fibres have different biopersistence characteristics, which may vary according to their respective manufacturing process and chemical composition. Current international efforts in developing standardized methodology for durability and biopersistence assessment of all industrial fibres are certainly opportune, as this parameter now appears to be an important element for carcinogenic risk evaluation and eventually occupational standards setting policy. Indeed, the 2001 IARC Monographs Programme to re-evaluate carcinogenic risks from airborne man-made vitreous fibres reinforces the concept that “high biopersistence of inhaled fibrous materials is correlated with high carcinogenicity”. The Monographs Working Group concluded that only the more biopersistent materials remain classified by IARC as possible human carcinogens. As a matter of fact, the labelling regulation in the European Union states that respirable particles with very short biopersistence can be exempted from the “carcinogen” label.
Results of the ongoing study by three laboratories in Switzerland, Germany and in the U.S.A. demonstrates that the half-time clearance for Canadian commercial chrysotile, i.e. the number of days necessary to eliminate half of the fibres remaining in the lungs after end of exposure, is about 15 days. This number is in accordance with other data published recently about chrysotile, and in line with epidemiology studies confirming that amphiboles are more fibrogenic and carcinogenic than chrysotile (amosite asbestos has a half-time clearance of ~ 466 days).
How does chrysotile compare with the most commonly used replacement fibres? Less durable, according to recent studies using the same methodology. For instance, ceramic fibre (RCF 1) has a half-time clearance of 60 days, aramid fibre around 90 days and cellulose fibre over 1000 days.
Fibre-Cement Without Chrysotile
On a worldwide scale, 95 % of the chrysotile used is for the manufacturing of asbestos cement products. This includes corrugated sheets, flat sheets, slates, pipes, etc.. Over the last decades, many materials were developed to compete with asbestos cement products (a/c), but they are not usually in the form of asbestos cement. For example, alternative pipe products are made with polyvinyl chloride (PVC) or ductile iron.
The characteristics of these products vary widely making it impossible to establish clear comparisons. However, it should be noted that no single fibre can replace chrysotile in all its diversified applications. Furthermore, their use is somewhat more limited and involves substantial economic restrictions compared to chrysotile. These would include price, health risk, durability, energy consumption and environmental considerations that are often higher than for chrysotile.
No fibre can easily replace chrysotile for the manufacturing of pipes. Tests were carried out with various materials, but none were satisfactory. Natural or synthetic fibres can therefore only replace chrysotile for the manufacture of flat or corrugated slates, however for the latter, the resistance provided by substitute fibres restricts manufacturing only the thickest sheets and with the highest level of corrugation.
Chrysotile and Portland cement have a binding property that cannot be matched by many materials. Introducing fibrous cement technology without chrysotile is therefore not easy. Dansk Eternit in Denmark and Supradur in the United States are faced with huge lawsuits due to the fast deterioration of their fibrous cement products that do not contain chrysotile. Similar tests on cellulose based composite products in Central America led to disastrous results and these products were quickly withdrawn from the market. Based on experiments carried out to date, it appears that fibre-cements that do not contain chrysotile are particularly sensitive to climatic conditions, particularly in hot and humid areas and areas with frequent freezing and thawing cycles.
Although experiments were carried out with a score of natural and synthetic fibres, only two, cellulose and the polyvinyl alcohol (PVA) resulted in any kind of commercial success. While the use of these products indoors does not seem to pose problems, their external use must be limited to areas with suitable climatic conditions.
In addition to the resistance and durability aspects, chrysotile-cement is less expensive than its competitors because chrysotile fibre is cheaper. Cellulose costs more than chrysotile. PVA is also very expensive.
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