Occurrence and risk of microplastics and hexabromocyclododecane in urban drinking water systems: From source water to tap water

The widespread presence of microplastics (MPs) in drinking water systems and their risk of releasing additives have caused widespread concern. However, current research on the migration and risks of MPs and additives in the complete drinking water supply chain remains inadequate. In this study, micro-Raman spectrometer was used to track the entire transport process of MPs from the water source to the tap water, with concentrations ranging from 805 to 4960 items/L, and polyethylene and Polyethylene terephthalate were dominant. The removal efficiency of MPs at the drinking water treatment plant was 85.0 ± 5.2 %. However, chlorination increased the proportion of polystyrene by 40.1 ± 5.3 %. Chlorination increases the surface roughness and carbonyl index of polystyrene standards, and promotes the release of hexabromocyclododecane (HBCD) (482.0 ng/g-2208.7 ng/g). The non-carcinogenic risk index of HBCD ingestion through drinking water remains well below 1 for residents. Complete water treatment processes significantly reduce the risks posed by MPs, achieving reductions of 54.3 % in the pollution load index and 82.1 % in the potential ecological risk index. The estimated daily intake of MPs ingested by residents through tap water ranges from 33.4 to 45.6 items/kg/d. This study investigated the occurrence of MPs in the complete drinking water supply chain and the risk of chlorine disinfection for HBCD release, which could help develop more effective MPs control measures and risk management strategies.