Paired measurements collected at the point of use in October and February were compared using a parametric test of mean difference for censored data, using the cen_paired() function in the NADA2 package. (Censoring here refers to lead concentrations below the reporting limit.) Duplicate measurements at sites within a single group were averaged; when one was observed and one censored, the duplicate measurements were re-censored at the midpoint value. Due to a log transformation of the data, back-transformed group differences are expressed as ratios. R code required to reproduce the analysis is provided as Supplementary Text S2, and data are available at doi.org/10.5281/zenodo.5139734.