Simultaneous determination of 11 haloacetic acids and oxyhalides by UPLC-HRMS in Human Serum, Breast Milk, and Urine

• Rapid and sensitive determination of HAAs and oxyhalides at trace levels. • First biomonitoring of highly toxic iodinated HAAs across multiple human matrices. • High concentration of chlorate in human urine reported for the first time. • Co-exposure correlations suggest synergistic DBP toxicity risks. Disinfection byproducts (DBPs), particularly haloacetic acids (HAAs) and oxyhalides, are of global concern due to their carcinogenicity and occurrence beyond drinking water. Biomonitoring data in human biological matrices remain scarce, especially for emerging iodinated DBPs. This study presents a validated analytical method for simultaneously quantifying 11 HAAs and oxyhalides in serum, urine, and breast milk. This method combines a tailored solid-phase clean-up with ultra-performance liquid chromatography–high-resolution mass spectrometry (UPLC-HRMS) and achieves excellent recoveries of 77-117%, low method detection limits of 0.01-0.20 μg/L, and acceptable matrix effects across all matrices. Applied to 122 biological samples collected in Beijing, this approach revealed several unprecedented findings: (i) mono-iodoacetic acid (MIAA), a highly toxic iodinated DBP, was consistently detected in all three matrices, marking the first such report in human biomonitoring; (ii) chlorate was detected in human urine for the first time, with a mean concentration of 117 μg/L, indicating overlooked exposure pathways; and (iii) significant correlations between HAAs and oxyhalides in biological samples suggest shared exposure sources or metabolic processes not previously documented. Serum exhibited the highest HAA concentrations, suggesting its high body burden. Chlorate and perchlorate were frequently detected at high concentrations in urine and breast milk, highlighting possible risks to vulnerable populations. This study addresses critical gaps in methodology and exposure data, providing a robust tool for DBP biomonitoring and key evidence for cumulative risk assessment beyond drinking water.