Fate, chlorination kinetics, and comprehensive risk assessment of pharmaceuticals and personal care products in...

The widespread occurrence of pharmaceuticals and personal care products (PPCPs) in aquatic environments has emerged as a global concern due to their potential threats to water security and ecological health. Despite increasing attention, their fate and associated risks in drinking water systems remain insufficiently understood. The occurrence, transformation behavior, and ecological and human health risks of 19 PPCPs were investigated across drinking water treatment and distribution systems in this study. Eighteen PPCPs were ubiquitously detected in raw water, with high detection frequencies (>70 %), whereas both the number of detected compounds and their concentrations were markedly reduced in finished water (five compounds) and tap water (eleven compounds). These results demonstrate the substantial effectiveness of conventional treatment processes in reducing both the diversity and concentrations of PPCPs. To further elucidate their potential transformation during water treatment, chlorination kinetics of eight structurally diverse PPCPs were evaluated under controlled conditions. Four compounds (atenolol, sulpiride, paroxetine, and nadolol) exhibited pseudo-first-order kinetics with residual chlorine, while the others exhibited significant resistance to chlorination. Degradation efficiency was found to depend on both the water matrix conditions and their molecular properties, highlighting the combined roles of intrinsic chemical properties and environmental complexity. Ecological risk assessment revealed ibuprofen posed a moderate ecological risk, a risk quotient (RQ) of 0.335, while triclocarban presented a high ecological risk (RQ = 4.6031). Mixture toxicity assessment based on the cumulative toxic unit (ΣTU) further indicated a potential ecological risk (ΣTU > 1) in raw water. Human health risk assessment showed minimal risks across all age groups (RQ 〈10^-3). However, infants were identified as the most susceptible population, likely due to their higher exposure relative to body weight. Among the detected PPCPs, meclofenamic acid was identified as the compound of highest concern, with average relative risk indices exceeding >10^-4. These findings provide critical insights into the fate and transformation of PPCPs in drinking water systems and offer scientific guidance for optimizing treatment processes and risk management strategies.