Chronic kidney disease of uncertain aetiology and its relation with waterborne environmental toxins: An investigation via compositional balances

The occurrence of environmental clusters of chronic kidney disease of uncertain aetiology (CKDu), where there is no known cause for the onset of kidney dys-function, is a concern globally. Waterborne exposure pathways in the environ-ment may result in indirect or direct ingestion of trace elements with potential health risks. This research examines the relationship between standardized inci-dence rates (SIRs) of CKDu and the log-ratio balances of potentially toxic ele-ments (PTEs) in regional stream water. Compositional elemental balances were created and regression was used to identify the balances most associated with log-transformed SIR CKDu. At the regional scale, a statistically significant rela-tionship was found between log(CKDu SIR) and the elemental balance Al/As which effectively delineates different geological domains across Northern Ire-land. Following stratification by basalt bedrock (the dominant bedrock geology for SIR CKDu), the balance Al/Fe was identified as significantly associated with log(CKDu SIR). Superficial deposits, dissolved organic carbon and pH may act as controls on the balance of Al and Fe. With a high proportion of private water supplies registered in these areas, this research highlights the importance of con-sidering bedrock geology and superficial deposits in understanding multi-element interactions of waterborne environmental toxins and potential links with environmental clusters of CKDu.