Question 6
Asbestos in Water: Does the use of asbestos-cement pipes contribute significantly to the presence of asbestos in water? Is there a risk associated with the presence of asbestos in drinking water?
Answer:
The use of asbestos-cement (A/C) pipes dates back to the early 1920ís, and it is estimated that by the end of the 1980's, close to 3 million kilometres of pipes will have been laid worldwide to convey potable water.
Highly aggressive waters may attack the cement matrix, and consequently lead to the release of fibres into the water circulating through the pipes, and A/C pipes are not recommended for use under such highly corrosive conditions, unless protected with specially designed internal protective lining.
The results of most studies published so far indicate that the source waters already contain asbestos fibres (mostly shorter than 1 u in length) before passing through the A/C pipe systems, often in numbers reaching several millions per liter, and it is generally agreed that A/C pipes do not appreciably raise the asbestos fibre content of water, and that the quantities found are within those which occur naturally.
As to the risk of health resulting from the presence of asbestos in potable water, results of several years of laboratory investigation in animals fed for their entire lifespan with very large (several billions of fibres every day) quantities of asbestos incorporated into their diet have consistently failed to indicate any raised incidence of gastrointestinal tumours, or of any other pathological changes in the gastrointestinal tract.
Epidemiological studies on human health effects related to asbestos levels in drinking water have failed to indicate any increased risk of alimentary tract tumours following the direct ingestion of asbestos fibres.
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References for Question 6:
Hallenbeck WH, Chen EH, Hesse CS, Patel-Mandlik K, and Wolff AH (1978). Journal of American Water Works Association. 70(2):97-102
A study of 15 water supply systems in the State of Illinois (U.S.A.) where some asbestos cement pipes were up to 50 years old, and where the water was non-aggressive to moderately aggressive, showing no significant differences before and after passing through the asbestos-cement pipe network.
MacRae KD (1988). Journal of the Royal College of Physicians of London 22(1):7-10
In this review article, the author concludes: "it would thus seem highly unlikely that the asbestos-cement pipe distribution system makes any biologically significant contribution to the asbestos content of water passing through it". "It is highly improbable that asbestos release from asbestos cement pipes is relevant to the development of cancer."
Millette JR, Craun GF, Stober JA, Kraemer DF, Tousignant HG, Hidalgo E, Duboise RL, and Benedict J (1983. Environmental Health Perspectives. 53:91-98
Some areas in Florida have been receiving drinking water through asbestos-cement pipes for 30-40 years. The authors mention: "No evidence for an association between the use of A/C pipes for carrying drinking water and deaths due to gastrointestinal and related cancers was found in this study".
Polissar L, Severson RK, Boatman ES and Thomas DB (1982). American Journal of Epidemiology 116(2):314-328
The site of the study was Puget Sound region of Western Washington, and the State's three largest metropolitan areas (Everett, Seattle and Tacoma) were used for comparison. Everett was the " high exposure municipality", where asbestos levels ranged from 37.2 to 556 million fibres per liter. Seattle and Tacoma had relatively low concentrations, averaging 7.3 million fibres per liter. The three metropolitan areas were subdivided into census tracts grouped by asbestos concentration. Data on cancer incidence were obtained from a surveillance registry; cancer mortality information came from death certificates. Duration of exposure to asbestos in drinking water was estimated and divided into long term (greater than 30 years) versus short term (less than 30 years) groups. Following the analysis of the results, the principal investigator, Dr. Lincoln Pollisar of the Fred Hutchinson Cancer Research Center, concluded that: "Results of this study and prior studies of cancer in relation to waterborne asbestos are inconsistent, and provide little evidence that asbestos in community water supplies has altered the risk of any cancer".
