Over 90% of the world production of chrysotile is used today to make chrysotile-reinforced cement. It has become an indispensable building material used around the world.
Chrysotile-cement is made by adding 10% to 15% chrysotile fibre to a mixture of Portland cement and water. It is a highly cost-effective material with high tensile strength and excellent compression resistance. It can with withstand alkalis, corrosion, heat, electrical conductivity and harsh weather. The reinforcing properties of chrysotile fibre greatly increase the durability of cement building products and permit the manufacture of thinner and lighter products.
Chrysotile-cement is used in some sixty industrialized and developing countries. Aside from its superior durability and performance, chrysotile-cement requires comparatively little energy to manufacture. Moreover, the principle raw material, Portland cement, is available almost anywhere in the world, which means that user countries may only need to import chrysotile fibre, thus reducing the drain on foreign currency reserves. More importantly, making the finished product domestically creates local jobs.
Chrysotile-cement is used in the form of flat sheets, corrugated sheets and roof coverings in residential, commercial and industrial construction, with the latter two accounting for a much higher proportion of sales. It is also used in making pipe for a variety of high and low pressure applications, including water distribution, sewer and irrigation systems. Chrysotile pipes can also be used as cable sheaths or as ducts for all types of industrial uses.
Are chrysotile-cement products dangerous to the general population?
What are fibre emissions like in or around buildings made with chrysotile-cement? Studies have shown that fibre levels measured around these buildings are no higher than in the vicinity of buildings made with other types of materials. As early as 1988, a group of experts brought together by the International Program on Chemical Safety (IPCS) concluded that high-density asbestos products, among them asbestos-cement sheets and asbestos panels, should not present risks of any significance under normal use; however, special precautions must be taken to control dust emissions during their installation and maintenance.
And what about asbestos in water resulting from the use of chrysotile cement pipe? Studies have shown that the use of chrysotile cement pipe contributes relatively little to the naturally occurring levels already in the water. And according to the World Health Organization (WHO), epidemiological studies of populations whose drinking water supply shows a high asbestos content reveal no evidence of ingested asbestos being carcinogenic. (Guidelines for Drinking Water Quality. World Health Organization Report, 1993.)
Is chrysotile-cement dangerous to workers?
The claim that modern products like chrysotile-cement are safe stems from the fact that studies of workers exposed to much higher dust levels than in today's factories show no excess lung cancer or mesothelioma (cancer of the pleura or peritoneum).
We now know that current technology can maintain a dust level (500 to 1,000 fibres/litre) below which the risk, if any, is so low as to be undetectable. This is what is called a practical threshold. At these levels, asbestos-related disease will simply become a thing of the past!
Current chrysotile-cement production is based on a wet manufacturing process and makes use of basic and simple control techniques cleaning, vacuuming and wetting. New product designs and installation techniques are helping to eliminate the need for on-site cutting and drilling, thus avoiding the primary source of dust. When cutting or drilling is required, low-speed or manual tools and wetting the materials will keep dust levels well below current exposure standards.
Environment emissions and waste
In the United States, the Clean Air Act has removed chrysotile cement from the list of emission sources requiring any further regulation, opting simply to retain a "no visible emissions standard". All solid or liquid products resulting from chrysotile-cement production, including packaging, can be recycled and reincorporated into the production process. Most countries consider non-friable chrysotile-cement waste to be inert, which means that it can be disposed of in municipal or industrial landfills, without risk of water or soil contamination. Modern chrysotile-cement plants can be considered models of environmental control and industrial hygiene; some have even won awards for their contribution to environmental protection in France, Nigeria, Bolivia and Pakistan.
Chrysotile vs Substitute Products: A question of performance and safety
While there are many other products currently used in residential and commercial construction, and for water distribution and sewerage, none matches the combination of technical and economic advantages of chrysotile-cement. Here is a short review of some of the alternative products on the market.
€ Non-asbestos fibre-cement
Development of this family of substitute products has run into many problems. The manufacturing cost is 20% to 30% higher, and many of the products have been demonstrated to be less resistant to heat, humidity and temperature contrasts (freeze-thaw) and thus not as durable as chrysotile-reinforced products. For example, Danish building product giant Dansk-Eternit is currently facing claims totalling in the hundreds of millions of dollars as a result of home owners being supplied defective corrugated roofing sheets using first-generation non-asbestos technology. Several Central American countries have also removed cement- and cellulose-based roofing materials from the market. Several complaints have also been filed in the United States and Great Britain against asbestos-free materials with poor technical performance or durability. Moreover, scientists have begun to raise concerns over the health effects of some of the fibres used to replace chrysotile. Many of these fibres, including cellulose are quite biopersistent, and thus require care during manufacture, handling and use.
€ Corrugated metal roofs
The production of corrugated galvanized iron sheets consumes 2 to 2-1/2 times more energy than chrysotile-cement. The figure rises even more when the energy content of coatings applied for aesthetic reasons and to prolong the durability of the products is factored in. When the longer service life of chrysotile-cement is factored in, coated galvanized iron sheet is estimated to consume about 5 times more energy than chrysotile-cement sheet production.
Studies have shown that, depending on the type of corrosion protection used, the useful life of corrugated iron roofing is significantly shorter (by one-quarter to one-third) than that of chrysotile-cement roofing. Not only is the maintenance of corrugated iron costly over time, it clearly has inferior acoustic and thermal insulation characteristics.
€ PVC (polyvinyl chloride)
The principal competing products for chrysotile-cement pressure pipe are PVC and ductile iron. PVC in particular has made great inroads in these markets. There is, however, growing attention from the medical and scientific communities on the potential health and safety risks of these materials. For example, vinyl chloride monomer (VCM) used in PVC is a well known human carcinogen that affects the brain and liver. VCM is also known to leach out of the pipe into drinking water. Furthermore, in developing countries, PVC pipe may contain lead as a stabilizing agent. Concerns have also been raised regarding the quantity of dioxins released into the environment during the production of PVC. In addition, several of the bonding agents used in the installation of PVC pipe are potential toxins.
Overall, the predicted durability of PVC is about 50 years. Chrysotile-cement pipe has an expected life of approximately 70 years. And for the same price, four times as much chrysotile-cement pipe can be installed. Moreover, it is known that PVC pipes do not stand up well to the climactic conditions of certain regions: a rise in water temperature or exposure to ultraviolet rays during storage and installation may damage them.
€ Ductile iron pipes
Ductile iron pipe is also not without risks. In its landmark ruling overturning the U.S. Environmental Protection Agency¹s asbestos ban, the U.S. Court of Appeals concluded that there is evidence that ductile iron is associated with cancer deaths. The EPA¹s own studies found that the population cancer risk for the production of ductile iron pipe may be comparable to the population cancer risk for the production of asbestos-cement pipe.
Like chrysotile-cement pipe, cast iron pipe with a protective coating has a useful life of about 70 years. The useful life of cast iron may be shorter in more aggressive soils or water, often because of the presence of corrosive agents.