Trace element analysis, model-based clustering and flushing to prevent drinking water contamination in public schools

Abstract

Drinking water samples taken from cafeteria sinks and water fountains in each of the 76 schools in the Winston-Salem/Forsyth County Schools (WSFCS) district (North Carolina, United States) were analyzed by inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) to determine As, Cd, Cr, Cu, Pb, Sb, Se and Tl. All samples from currently active schools tested below the maximum contaminant level (MCL) set for each element. Model-based clustering was employed to identify schools more prone to drinking water contamination. This multivariate approach may be used in a prevention program that can be tailored to specific school districts, with each school tested at a frequency compatible with its contamination risk level. Water flow stagnation during the summer break results in higher elemental concentrations in school drinking water, but a simple 5-60 min flushing procedure significantly reduces the contamination levels.