Asbestos is a health risk when extremely fine particles become airborne and are inhaled. These respirable fibres cannot be seen with the eye, but they can enter and become lodged in the lungs, where they may stay and develop into a disease. The fibres are usually:
less than 3 microns* in diameter and
greater than 5 microns in length.
*(1 micron = 1/1000 of a millimetre)
The presence of asbestos materials in a building does not necessarily create a health risk. While the materials are undisturbed and in sound condition, they will not generate airborne respirable fibres or create a health risk.
The likelihood of any particular person developing an asbestos-related illness depends on a number of factors, including:
length of time a person is exposed to airborne asbestos fibres
concentration or levels of asbestos in the air breathed
size and type of asbestos fibres
influence of other factors, especially cigarette smoke. (Research has shown that smoking significantly increases the risk of lung cancer in people who have been exposed to asbestos.)
Drinking water has often been transported in high pressure asbestos-cement pipes or collected into household tanks from asbestos cement roofing material. The risk posed by the long-term consumption of such water has been studied extensively. Data from both animal experimentation and human epidemiological studies has shown that the risk of asbestos-related disease is not increased.
Also, studies show that ingested asbestos fibres very rarely penetrate the gastrointestinal mucosa. Taking into account all of this information, it would appear that the carcinogenic effect of drinking water contaminated by asbestos is very small, if not zero.