Lead release to potable water during the Flint, Michigan water crisis as revealed by routine biosolids monitoring data

Water Res. 2019 Sep 1;160:475-483. doi: 10.1016/j.watres.2019.05.091. Epub 2019 May 27.


Routine biosolids monitoring data provides an independent and comprehensive means to estimate water lead release pre-, during and post-Flint Water Crisis (FWC). The mass of potable plumbing-related metals (i.e., lead, cadmium, copper, nickel and zinc) in sewage biosolids strongly correlated with one another during the FWC (p < 0.05). A simple parametric regression model based on 90th percentile potable water lead measurements (WLL90) from five city-wide citizen science sampling efforts August 2015-August 2017 was strongly correlated to corresponding monthly lead mass in biosolids [Biosolids-Pb (kg) = 0.483 x WLL90 (μg/L) + 1.79; R2 = 0.86, p < 0.05]. Although total biosolids lead increased just 14% during the 18 months of the FWC versus the comparable time pre-FWC, 76% of that increase occurred in July-September 2014, and the corresponding percentage of Flint children under 6 years with elevated blood lead ≥ 5 μg/dL (i.e., %EBL5) doubling from 3.45% to 6.61% in those same three months versus 2013 (p < 0.05). %EBL5 was not statistically higher during the remaining months of the FWC compared to pre-FWC or post-FWC. As expected, lead in biosolids during the FWC, when orthophosphate was not added, was moderately correlated with water temperature (R2 = 0.30, p < 0.05), but not at other times pre- and post-FWC when orthophosphate was present. Tripling the orthophosphate dose post-FWC versus pre-FWC and some lead pipe removal, decreased lead in biosolids (and %EBL5) to historic lows (2016-2017 vs. 2012-2013; p < 0.05), supporting the effectiveness of these public health interventions in reducing childhood water lead exposure.

Keywords: Biosolids; Blood lead levels; Flint water crisis; Lead corrosion; Lead exposure.

MeSH terms

  • Child
  • Cities
  • Drinking Water*
  • Humans
  • Lead
  • Michigan
  • Water Supply


  • Drinking Water
  • Lead