Significance of Mg-hardness and fluoride in drinking water on chronic kidney disease of unknown etiology in Monaragala, Sri Lanka.

The epidemic of chronic kidney disease of unknown etiology (CKDu) that contributes significantly to morbidity and mortality rates among dry-zonal farming communities has become a public health priority in Sri Lanka. Though a large number of hypotheses were introduced as causative factors, none of them have been confirmed so far. As drinking water quality is among the most suspected causative factors for the emergence of CKDu, a detailed hydro-geochemical investigation was carried out concurrently with the population screening in the Monaragala district of Sri Lanka where high incidences of CKDu are reported. A population screening was performed selecting 46,754 people using both dipstick proteinuria test and Albumin-Creatinine Ratio (ACR). The results revealed that the disease prevalence is about 6.7 % in the district. A total of 60 groundwater samples, 30 each, were collected from CKDu-prevalent locations and control locations where there are no CKDu cases reported. The samples were analyzed to identify any possible linkage between water quality and disease prevalence. Concentrations of hardness, F ^- , Na ^+, and Mg ²⁺ in groundwater revealed a statistically significant difference between CKDu and control wells at a confident level of p = 0.05. The study revealed that alkali (Na ⁺ +K ⁺ ) and alkaline earth cations (Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ ) were relatively higher in drinking water sources used by CKDu patients, compared to the well waters used by healthy individuals. Nearly 87 % of the wells used by CKDu cases showed higher fluoride levels that exceed the threshold level (1.0 mg L ^-1 ). Contents of nephrotoxic trace elements such as As, Cd, and Pb were found to be comparable in both types of wells and were well below the WHO permissible levels, thus negating their prime influence on the CKDu prevalence. It is obtrusive that the elevated fluoride levels together with water hardness associated with higher Mg ²⁺ levels have a possible relation with CKDu and may influence the disease progression.
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