Health implications of PAH release from coated cast iron drinking water distribution systems in The Netherlands.

BACKGROUND: Coal tar and bitumen have been historically used to coat the insides of cast iron drinking water mains. Polycyclic aromatic hydrocarbons (PAHs) may leach from these coatings into the drinking water and form a potential health risk for humans. OBJECTIVE: We estimated the potential human cancer risk from PAHs in coated cast iron water mains. METHOD: In a Dutch nationwide study, we collected drinking water samples at 120 locations over a period of 17 days under various operational conditions, such as undisturbed operation, during flushing of pipes, and after a mains repair, and analyzed these samples for PAHs. We then estimated the health risk associated with an exposure scenario over a lifetime. RESULTS: During flushing, PAH levels frequently exceeded drinking water quality standards; after flushing, these levels dropped rapidly. After the repair of cast iron water mains, PAH levels exceeded the drinking water standards for up to 40 days in some locations. CONCLUSIONS: The estimated margin of exposure for PAH exposure through drinking water was > 10,000 for all 120 measurement locations, which suggests that PAH exposure through drinking water is of low concern for consumer health. However, factors that differ among water systems, such as the use of chlorination for disinfection, may influence PAH levels in other locations.

Tools to monitor corrosion of cement-containing water mains.

Approximately 40,000 km of the drinking water network in The Netherlands consists of asbestos cement water pipes. The number of fractures in these pipes has increased greatly in recent years. This is due to corrosion of the asbestos cement (AC) which affects the condition of the pipe. Every time a fracture occurs, the question is raised of whether the pipe in question has to be replaced or repaired. A relatively simple destructive technique and non-destructive tests are used on a large scale to assess the condition of the AC pipes in use. Not only is corrosion detrimental to the pipes themselves, it also influences the water quality. Corrosion of the inner walls of cement-containing pipes involves the leaching of hydroxides. This causes pH changes resulting in scaling in water mains and domestic installations. Monitoring techniques have been developed to determine the effects of leaching on water quality. The large-scale use of the relatively simple techniques at water companies increases insight into the condition of the drinking water network, the life expectancy of the pipes and the effects of corrosion on the water quality. Applying these techniques enables those involved to make decisions on pipe replacement and to provide solutions for reducing the effects of leaching.

Scaling in domestic heating equipment: getting to know a complex phenomenon.

Excessive scaling is one of the main nuisances in relation to the use of drinking water. Ever more water companies try to minimise scaling. Although scaling is an old problem, prediction of scaling has been proven to be very tricky. Traditionally, the (Langelier) Saturation Index is used to evaluate scaling properties of drinking water. From experience it is well known that this parameter is not suitable for proper prediction. New parameters have been developed and standardised for scaling prediction, namely the Calcium Carbonate Precipitation Potential, calculated at a temperature of 90 degrees C (CCPP90); the Saturation Index, also calculated at a temperature of 90 degrees C (SI90); the Nucleation Index (NI) and the Measured Calcium Carbonate Precipitation (MCCP). These parameters are currently successfully used in The Netherlands. The development of new parameters to predict scaling in domestic heating equipment has resulted in a better understanding of processes involved. Even now unexpected and at first sight contradictory results are obtained frequently. With the use of the developed measuring techniques, solutions may be found to combat excessive scaling.