Comparative Cytotoxicity of Six Iodinated Disinfection Byproducts on Nontransformed Epithelial Human Colon Cells

Exposure to disinfection byproducts (DBPs) in chlorinated drinking water has been positively associated with increased risk of colon, bladder, and rectum cancers. Iodinated DBPs (I-DBPs) are of concern as this class exhibits enhanced cytotoxicity and genotoxicity compared to those of chlorinated and brominated equivalents in Chinese hamster ovary (CHO) cells. We tested the impact of six I-DBPs on immortalized normal human colon epithelial cells (CCD 841 CoN). Our assay showed the following rank order of cytotoxicity of the I-DBPs: iodoacetic acid (IAA) > iodoacetamide (IAcAm) > bromoiodoacetamide (BIAcAm) > chloroiodoacetamide (CIAcAm) > bromoiodoacetic acid (BIAA) ≈ diiodoacetic acid (DIAA). The enhanced cytotoxicity of IAA compared with those of other haloacetic acids agrees with studies conducted on CHO cells. IAcAm was found to be 3.5 times more cytotoxic than BIAcAm and 9.4 times more cytotoxic than CIAcAm. The cytotoxicity of both dihaloacids (i.e., BIAA and DIAA) was <1% of that of the monohaloacid IAA. Apart from IAA, the nitrogenous I-DBPs demonstrated cytotoxicity greater than that of the carbonaceous I-DBPs. The results are consistent with previous CHO studies of dihalogenated I-DBPs but not monohalogenated ones. This study has implications for drinking water management strategies aimed at minimizing the formation of I-DBPs associated with enhanced cytotoxicity

Expanding Per- and Polyfluoroalkyl Substances Coverage in Nontargeted Analysis Using Data-Independent Analysis and IonDecon

Per- and polyfluoroalkyl substances (PFAS) are widespread, persistent environmental contaminants that have been linked to various health issues. Comprehensive PFAS analysis often relies on ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC HRMS) and molecular fragmentation (MS/MS). However, the selection and fragmentation of ions for MS/MS analysis using data-dependent analysis results in only the topmost abundant ions being selected. To overcome these limitations, All Ions fragmentation (AIF) can be used alongside data-dependent analysis. In AIF, ions across the entire m/z range are simultaneously fragmented; hence, precursor–fragment relationships are lost, leading to a high false positive rate. We introduce IonDecon, which filters All Ions data to only those fragments correlating with precursor ions. This software can be used to deconvolute any All Ions files and generates an open source DDA formatted file, which can be used in any downstream nontargeted analysis workflow. In a neat solution, annotation of PFAS standards using IonDecon and All Ions had the exact same false positive rate as when using DDA; this suggests accurate annotation using All Ions and IonDecon. Furthermore, deconvoluted All Ions spectra retained the most abundant peaks also observed in DDA, while filtering out much of the artifact peaks. In complex samples, incorporating AIF and IonDecon into workflows can enhance the MS/MS coverage of PFAS (more than tripling the number of annotations in domestic sewage). Deconvolution in complex samples of All Ions data using IonDecon did retain some false fragments (fragments not observed when using ion selection, which were not isotopes or multimers), and therefore DDA and intelligent acquisition methods should still be acquired when possible alongside All Ions to decrease the false positive rate. Increased coverage of PFAS can inform on the development of regulations to address the entire PFAS problem, including both legacy and newly discovered PFAS