PAHs in Coated Cast Iron Mains

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. In a Dutch nationwide study we took drinking water samples at 120 locations over a period of 17 days under various operational conditions, such as undisturbed operation, during flushing, and after a mains repair, and analysed these samples for PAHs. During flushing, PAH levels frequently exceeded drinking water quality standards. After flushing, these levels dropped rapidly. After the cut and repair of cast iron mains, PAH levels exceeded the drinking water standards for up to 40 days after the repair. We estimated the health risk associated with an exposure scenario over a lifetime period. The margin of exposures of PAHs through drinking water are well above 10,000 for all 120 measurement locations under the cautious assumption of relatively long exposure times. This indicates that PAH exposure through drinking water is of only low concern for consumer health.