Molecular linkage of dissolved organic matter in groundwater with prevalence of chronic kidney disease with unknown etiology

Chronic kidney disease of unknown etiology (CKDu) is receiving considerable attention throughout the world due to its severe threat to human health. However, the linkage between dissolved organic matter (DOM) in groundwater to CKDu is still unclear, especially at molecular level. Herein, the molecular differences of DOM between groundwaters related to CKDu (CKDu groundwater) and to non-CKDu (non-CKDu groundwater) in CKDu-prevalence areas and control area from Sri Lanka were unraveled by Fourier transform ion cyclotron resonance mass spectrometry. Compared with DOM in non-CKDu groundwater, DOM in CKDu groundwater was more unsaturated, oxidized, biologically refractory, and high-molecular-weight, and contained more aromatics (AS, 15.4%) and less aliphatics (AL, 8.2%), which was probably related to the recharge of surface water. The enrichment of biologically refractory DOM in CKDu groundwater might encompass toxic substances. Furthermore, the ratios of AS to AL (AS/AL) in groundwater were positively correlated with Ca²⁺, F⁻, and Si (r ≥ 0.66) that were generally associated with CKDu. It is explained that aromatic substances might be toxic by forming a complex with cation (Ca²⁺) and aliphatic substances could facilitate release of toxic anions (F⁻) in CKDu groundwater. According to the above findings and the receiver operating characteristic (ROC) analysis, the groundwater with AS/AL value larger than 1.43 are unsafe and likely to cause CKDu. The linkage between CKDu and specific DOM molecules provides scientific support for constructing a quick early screening of potential CKDu groundwater and helps ensure the safety of drinking water. Graphical Abstract: [Figure not available: see fulltext.].