3 Use and effects of Asbestos cements in developing countries
In the previous sections it has been illustrated that the quantitatively dominating use of Asbestos fibers occurs in Asbestos cements. The wide distribution of fibrous cement products in DC leads to the suspicion that an elevated Asbestos emission is also to be expected there. In the following, fiber emitting processes for the processing and use of Asbestos cement are discussed.
Asbestos cements are primarily used as construction material in many forms (see Part II, Section 4.1). The processing methods are also manifold. With all of these options, the methods can essentially be divided into two groups, in which differing mechanisms are effective, which can be evaluated differently in regard to potential Asbestos dust emissions.
1. Cutting processes with manual tools and slowly running machines, at which Asbestos cement wastes arise in the form of rough swarf and scraps. With these processes larger attached areas of Asbestos cement structure remain.
2. Grinding and sawing processes using fast operating machines, at which the original material structure is totally destroyed. With this type of processing the structure is beaten to fine dust, and with certainty a change can be expected in the original fiber geometry of the Asbestos in the sense of a distribution into finer and shorter fiber elements.
Consideration of the health and safety measures in handling Asbestos described in Part II, Chapter 5, is important. It is suspected that in DC these are often not applied or only insufficiently applied. Further information on this is provided in the individual country profiles.
With regard to Asbestos emission through use of Asbestos cement products, erosion and weathering processes particularly play a role. Included here are: flat and corrugated panels as roofing, shingles as facing panels and for roofing, panels as facade elements as well as pipes for water installations.
Chemical and physical weathering mechanisms are in effect on these products, leading in some cases to a destruction of the cement matrix. The result is an exposure of Asbestos cement so that Asbestos fibers can be released to the environment by wind or water erosion. These phenomena are more favorable in areas with extreme climatic stresses, such as high relative humidity, rain periods and high temperatures.
The great amount of roofing and facade panels applied in DC poses the danger of fiber emissions from the weathering of Asbestos cements. The use of Asbestos cements in the area of water main pipes causes the danger of Asbestos contamination of drinking water. However, it must be added that a fiber concentration of up to 20,000 fibers per liter is acceptible from a toxicological standpoint, since the oral intake is judged much less critical in comparison to the inhalative intake. This is not a specific problem of the DC, though, since also in industrialized countries Asbestos cements have been and are used in water mains.
Annex 3 shows the average Asbestos concentrations resulting from different processes.
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