title: Direct and indirect photodegradation pathways of cytostatic drugs under UV germicidal irradiation: Process kinetics and influences of water matrix species and oxidant dosing.
abstract: The ever-increasing consumption of various cytostatic drugs (CSDs) has attracted growing public concern in recent years. The photodegradation of 8 CSDs was investigated using a low-pressure UV-254Hg lamp, resulting in fluence-based first-order kinetic rate constants in the range of (0.20-6.97)×10-4cm2mJ-1. The influence of water matrix components, including natural dissolved organic matter (DOM), bicarbonate (HCO3-), nitrate (NO3-), chloride (Cl-), and sulfate (SO42-), was investigated. The degradation rates of CSDs decrease in the presence of DOM due to the competition for the UV light, but increase with addition of NO3-due to an indirect production of HO. Further investigation was carried out to evaluate the viability of UV treatment performances using two real water samples, namely treated water from a water treatment plant and secondary effluent from a wastewater treatment plant. The primary photodegradation byproducts of CSDs were identified using LC/MS/MS to investigate the mechanism of direct UV photolysis and indirect NO3--induced and DOM-induced photolysis. The degradation rates of CSDs increase significantly with the addition of H2O2or S2O82-under UV irradiation, due to the generation of non-selective HO or selective SO4-. As an electrophilic radical, SO4-mainly reacts via electron transfer and selectively attacks certain electron-donating functional groups of CSDs.
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639789, Singapore; Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639789, Singapore; Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
authors.forename: Jiefeng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Water Research Analytical Laboratories, Water Quality Office, Public Utilities Board, 82 Toh Guan Road East, #04-03, Singapore 608576, Singapore.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Xiao
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639789, Singapore; Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
authors.forename: Victor W C
authors.initials: VW
authors.lastname: Chang
authors.affiliation: School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639789, Singapore; Nanyang Environment and Water Research Institute (NEWRI), Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore. Electronic address: cttlim@ntu.edu.sg.
authors.forename: Teik-Thye
authors.initials: TT
authors.lastname: Lim
mesh_terms: D054697:Cytostatic Agents / Q000032:analysis* / Q000528:radiation effects; D007700:Kinetics; D008962:Models, Theoretical; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry*; D010782:Photolysis; D014466:Ultraviolet Rays; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D054697:Cytostatic Agents; D016877:Oxidants; D062065:Wastewater
keywords: Cytostatic drugs; Degradation pathway; UV photolysis; Water matrix