3.4 Other health hazards
The above named diseases can be considered the "classical" Asbestos-caused diseases. The cause-effect relationship has been confirmed. In contrast, there is not complete epidemiological verification of this relationship for other diseases (malignant tumors e.g. of the urinary bladder, the gastrointestinal tract, the larynx, the esophagus), whose causes are traced to Asbestos handling. Due to the complexity of the cause-effect relationships and the multitude of other possible influences, a selective causal relationship between Asbestos exposure and the listed diseases is very hard to methodically prove.
Oral intake of Asbestos fibers is considered by some researchers to be another health risk. An existing Asbestos contamination of drinking water from geogenic background contamination can be differentiated from that due to Asbestos containing cement pipes. Asbestos cement pipes have been used for drinking water conduits and for wastewater sewers for over 100 years. They contain about 10-15 wt.-% Asbestos fibers, usually chrysotile. The possibility that Asbestos fibers will be released and enter the drinking water is given through mechanical and chemical wear. For instance, the layers can be damaged through the grinding effect of sand. In 1974 the American Water Work Association investigated the danger of fiber release from intact pipe connections and could not find any evidence for this. However, in old pipes (> 30 a), particularly unlayered pipes, and/or as a consequence of a pipe burst (e.g. due to frost), continual or periodic releases of Asbestos fibers can occur. An elevated Asbestos fiber release rate is particularly expected with the presence of chemically aggressive water. It has been proven that the binding of hardened Asbestos cement can chemically react with different liquids and gases (for example with NH4+ and Mg-salts, high sulfate-concentrations, humine acids, carbonic acid, etc.). The strength of the cement matrix can be reduced through the reactions, and the binding impaired or partly destroyed by the dissolution of individual components. As a consequence, a significantly higher amount of Asbestos fibers can be released. To prevent this process, it is recommended to exactly determine the drinking water chemistry with respect to pH and carbonate saturation.
International literature on oral intake of Asbestos fibers via the gastrointestinal tract and the resulting effects has grown to nearly 200 works (Martels/Schormann, in Asbest-Handbuch, No. 4570, Asbest im Trinkwasser und ihre Bewertung (Asbestos in Drinking water and ids Evaluation)). Epidemiological studies on the effects of oral intake of Asbestos fibers have been performed in different countries, in particular Canada and the U.S.A., without being able to prove significant relationships to increased cancer cases or increased mortality, although in some cases very high Asbestos fiber values in drinking water were present (up to several million fibers per liter) (UBA-Reports 5/91). These investigations can be distinguished as follows:
• Asbestos contamination through natural sources
• Contamination by Asbestos mining (Duluth-Studies)
• Contamination of drinking water by Asbestos water pipes
Only the San Francisco-Bay-Studies (Kanarek, Conforti et al.) provide through the results of linear regression analyses indications of a causal relationship between cancer of the gastrointestinal tract and the oral intake of Asbestos fibers through water, food and beverages. However, since these results are overlaid with a number of other factors, the explanation of the factor "oral intake of Asbestos fibers" for the cancer arisings is doubted by a number of scientists.
In the Federal Republic of Germany the measured Asbestos fiber concentrations in drinking water range from < 5,000 up to 60,000 fibers per liter (UBA-Report 5/91). However, it should be noted that these fiber concentrations cannot be viewed as representative for Germany, since they are the result of 38 samples.
Numerous investigations confirm that the Asbestos concentrations in drinking water vary greatly from that in the air. They are generally much thinner and shorter than in the air (median values for the fiber length are between 0.5 ym and 0.8 km in water, the diameter lies between about 0.03 ym and 0.08 ym). The amount of fibers potentially released from the water into the air (e.g. by showering, cleaning, etc.) is largely agreed by all researchers to be classified as relatively unhazardous to the health. Research performed in the U.S.A., however, shows that with very heavily Asbestos-contaminated drinking water (fiber concentrations between 10(6) and 10(13) FA), fiber concentrations in the surrounding air inside houses were found up to 52,000 F/m³ (in comparison: in residential buildings with low Asbestos-containing water only 7,600 Faser/m³),. and the outdoor air of these very heavily contaminated houses showed values of up to 20,000 F/m³. Within buildings peak values of up to 240,000 F/m³ (during vacuuming) were measured.
With regard to the arising health hazard, it should be pointed out that due to the shorter fibers, the danger of intake through inhalation is decreased. (Usually fibers had lengths < 0.5 km; the average fiber length was FL = 0.61 ym; for comparison: in the few less contaminated residences FL = 0.81 ym). Nevertheless, with the optimistic assumption of just 2 % of the fibers having a length > 5 ym, a contamination of cat 1,000 F/m³ is calculated, which represents the tolerable value for a lifelong contamination as defined by the German Federal Health Agency (Bundesgesundheitsamt).
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