Sources of Asbestos in Drinking Water

In the water supply chain, asbestos can be introduced at two stages:

Pre-treatment: Asbestos may be introduced into water by the dissolution of asbestos-containing minerals and ores (geologic erosion) as well as from industrial effluents and atmospheric pollution. However, water filtration processes, when operated properly, have been shown to substantially reduce asbestos fibre concentrations in drinking water. For instance, diatomaceous earth filtration can remove both amphibole and chrysotile fibres, with demonstrated removals as high as 99.99%.

Post-treatment: the use of AC pipes is associated with the release of asbestos fibres into drinking water at post water treatment phase. This is a major concern because fibres released post treatment are not eliminated at all. They therefore end up in the distribution points. The amount of asbestos introduced into the distribution system depends on various factors.

Age: The service life expectancy of AC is estimated to be roughly 50 years. While the Chrysotile Institute estimates AC pipe lifespan at 70 years, actual service life depends on pipe condition and working environment. The service life expectancy of most AC pipes depends on many factors such as construction methods, quality of pipe manufacturing, soil corrosivity and water chemistry.

Aggressiveness of water supply: High water flows in the distribution system can lead to the erosion of AC pipes walls. This results in elevation of asbestos fibre counts in water. High flows caused by flushing or firefighting can stir up sediment in AC mains. If this occurs in generally low-flow areas, fibre counts can rise to 10 or even 100 times typical values (Logsdon,1983).

Distribution system operation and maintenance procedures: Unless the pipes are flushed out under pressure, drilling and tapping of AC pipes can introduce and elevate asbestos containing debris into distribution systems.