Formation of iodo-trihalomethanes, iodo-haloacetic acids, and haloacetaldehydes during chlorination and chloramination of iodine containing waters in laboratory controlled reactions

Iodine containing disinfection by-products（I-DBPs） and haloacetaldehydes（HALs） are emerging disinfection by-product（DBP） classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes（I-THMs）,iodo-haloacetic acids（I-HAAs） and selected HALs（mono-HALs and di-HALs species, including iodoacetaldehyde） were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

Chlorinated Polyfluoroalkyl Ether Sulfonic Acids(Cl-PFESAs)Are Associated with Eye Diseases in Humans and Eye Toxicity in Zebrafish

Evidence from animal experiments has shown that chlorinated polyfluoroalkyl ether sulfonic acids(Cl-PFESAs)can induce vision dysfunction in zebrafish.However,environmental epidemiological evidence supporting this hypothesis remains limited.In our case−control study,samples collected from 270 individuals(135 controls and 135 cases)from the Isomers of C8 Health Project data were analyzed for Cl-PFESAs.We also repeated our analysis on zebrafish to support our findings in humans and to decipher the mechanism underlying Cl-PFESA eye toxicity.The serum levels of per-and polyfluoroalkyl substances(PFASs)and alternatives were significantly higher in the cases than in the controls.Higher serum Cl-PFESA levels were associated with greater odds of eye diseases,and the trend showed a statistically significant dose-dependent relationship.The Shapley additive explanations(SHAP)value indicated that 8:2 Cl-PFESA was the dominant eye disease risk factor among the 13 studied PFASs.In zebrafish experiments,Cl-PFESAs induced eye toxicity in adult zebrafish by oxidative damage and cell apoptosis.Compared to the control group,there was significantly reduced thicknesses of the inner plexiform layer(IPL),outer plexiform layer(OPL),and retinal tissue in the zebrafish exposed to Cl-PFESAs.Our study provides human clinical and animal experimental data,showing that exposure to PFASs increases the odds of the development of eye toxicity.