Cytotoxicity and Genotoxicity toward Mammalian Cells Induced by Organic Iodine in Peroxymonosulfate (PMS) Processes: Activated PMS Is Better than Nonactivated PMS in Mitigating Toxicity

Peroxymonosulfate (PMS) and its activation processes have been extensively studied. However, iodinated byproducts (I-DBPs) generated during nonactivated PMS (NPMS) and activated PMS (APMS) processes pose a significant risk. In NPMS, a 50 μg/L concentration of iodide (I^–) could significantly (p < 0.05) increase the cytotoxicity of both the Suwanee River natural organic matter (SRNOM) solution and wastewater secondary effluent (SE), at the dose of 0.5 mM PMS. Cytotoxicity and genotoxicity of the SRNOM solution increased by 6.6 mg-phenol/L and 2.4 μg-4-NQO/L with 200 μg/L I^–. For wastewater secondary effluent (SE), both toxicities increased 2.4-fold and 1.9-fold. APMS reduced cytotoxicity by 42–47% and genotoxicity by 53–60% compared with NPMS in I^–-containing SRNOM and SE samples. NPMS promoted adsorbable organic iodine (AOI) formation, while APMS inhibited AOI by 77.5–84.9%. FTICR-MS showed NPMS favored I-DBP generation with aromatic precursors, whereas APMS eliminated these precursors and I-DBPs. Compounds such as p-iodophenol and 4-methyl-2-iodophenol were detected in NPMS but removed in APMS. NPMS exhibited weaker oxidation, producing tannic acid-like, lignin-like, and protein-like precursors that can increase toxicity when reacting with HOI. Conversely, APMS enhanced oxidation via hydroxyl radicals and singlet oxygen, decomposing these precursors further. Importantly, APMS also converted HOI into nontoxic iodate, reducing overall toxicity in I^–-containing water.