Comment on "Water sources and kidney function: investigating chronic kidney disease of unknown etiology in a prospective study", by P. Vlahos et al

Abstract

Vlahos et al., Ref. 1, NPJ Clean water. 4, 50 (2021) have reported the presence of pesticide contamination above safe levels in a "single time-point analysis" of well water in a region in Sri Lanka where chronic kidney disease of unknown etiology (CKDu) is endemic. They conclude "that agrochemical use in paddy and other agricultural practices ... of the Green Revolution in Sri Lanka may now be contributing to ill health, rapid progression of disease, and mortality". The authors also propose "reducing ... agrochemical contaminants in Sri Lanka and other tropical countries to reduce ... CKDu". These conclusions, based on what they call a "single time-point analysis", tantamount to an identification of the etiology of CKDu are unsupported by the evidence presented by Vlahos et al. They do not satisfy, say, even the simplest of Bradford-Hill criteria for causation. In particular, (i) similar but non-persistent pesticide excesses have been detected sporadically in most parts of the country including where there is no CKDu; (ii) the pesticides reported in (1) cause both hepatotoxicity and nephrotoxicity; the latter with glomerular damage while CKDu is associated with tubulo-interstitial damage where no hepatotoxic symptoms have been reported; (iii) the pesticides detected have short half-lives and are used over short periods during farming; so the one time-point analysis is inadequate and misleading; (iv) farming communities that use pesticides in the same way but remain essentially without CKDu are found to exist adjacent to communities with CKDu; (v) the CKDu prevalence seems to correlate with local geomorphology but without correlation to agriculture which is practiced in most parts of the country. .