  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. .
