CHAPTER 4: Ocurrence of Polycyclic Aromatic Hydrocarbons (PAHs) and Their Chlorination By-Products in Drinking Water and the Coatings of Water Pipes

Polycyclic aromatic hydrocarbons (PAHs) can be formed during incomplete combustion of organic materials and occur in products derived from fossil fuels such as coal tar or asphalt. The presence of PAHs in drinking water is rarely originating from raw water but from the water distribution systems. Indeed, until the 1970s, steel and cast iron water pipes in Europe were commonly lined with coal tar pitch to prevent corrosion. Although coal tar was then replaced by other materials, many coal tar lined systems are still in use today. Coal tar contains PAHs which have been shown to migrate in drinking water. Although water chlorination has been proven effective in reducing PAHs levels, this type of disinfection can formed chlorinated, hydroxylated and oxidised by-products. These reaction products exhibit greater toxicity than their PAHs precursors. The aim of this study was to assess the potential exposure to PAHs and their by-products due to drinking water. Several sampling campaigns were conducted in French communities with a drinking water distribution network known for recurrently showing not negligible PAHs concentrations. Seventeen PAHs and 11 potential chlorinated by-products were analysed in drinking water samples from two distribution networks using different disinfection agents (ClO₂ and chlorine). The analysis of presumably coal tar-based pipe coatings of two pipe sections was also performed. The analytical method was based on solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MSⁿ). The limit of quantification was 10ng/L for all target compounds. PAHs with less than five aromatic rings were the most frequently detected in all studied networks although the individual compositions varied. Five PAHs chlorination by-products (anthraquinone, fluorenone, cyclopenta[d,e,f]phenanthrenone, 3-chlorofluoranthene, and 1-chloropyrene) were identified, their presence is closely correlated to that of their respective precursor. In the coatings, the same PAHs and chlorination by-products found in drinking water were observed, suggesting that the reaction of PAHs with disinfectant agents takes place in the coatings and not in the water phase after migration. To our knowledge, this is the first time that chloropyrene and cyclopenta[d,e,f]phenanthrenone were found in drinking water and linked to reactions of chlorine with constituents of coal tar pipe coatings.