Glyphosate and Fluoride in High-Hardness Drinking Water Are Positively Associated with Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka

Chronic kidney disease of uncertain etiology (CKDu) has emerged as a serious public health concern in farming communities globally, especially in Sri Lanka with 5%-20% of the adult population affected by the disease in CKDu-endemic regions. It is hypothesized that drinking water contamination of glyphosate in combination with water hardness and co-occurring trace elements contribute to CKDu in Sri Lanka. However, no studies to date have comprehensively examined this hypothesis. Here, we conducted a large field study to measure and compare drinking water chemical burden in CKDu-endemic areas with CKDu-nonendemic areas in rural Sri Lanka. Chemical measures of water quality included glyphosate, water hardness, and trace elements, including fluoride. Glyphosate was detected in 44% of endemic wells and 8% of nonendemic wells. Fluoride was detected in 99% of endemic wells and 80% of nonendemic wells. Logistic regression revealed that the presence of elevated glyphosate, fluoride, hardness, and vanadium in wells was positively associated with CKDu prevalence. The co-occurrence of glyphosate and high hardness indicate potential complexation of glyphosate in wells from CKDu-endemic areas. Collectively, our work represents the first definitive assessment of glyphosate presence in regions with geogenic high water hardness and fluoride and demonstrates a strong correlation with CKDu incidence.