Analysis of blood lead levels of young children in Flint, Michigan before and during the 18-month switch to Flint River water

Background: The toxicity of lead, like any xenobiotic, is directly linked to the duration of exposure and toxin concentration in the body. The elevation in blood lead levels (BLLs) in young Flint, Michigan children noted in time-periods before, and during the 18-month exposure to Flint River water (FRW) from 25 April 2014 to 15 October 2015 is well-known internationally. The length of time BLLs were elevated is unknown, yet key in understanding the potential health impact of the event. The objective of this study was to evaluate whether BLLs in Flint children were increased during the entire 18-month FRW exposure compared to similar earlier time periods. Methods: We conducted a retrospective study analyzing BLLs from Flint children aged 5 years and under. The geometric mean (GM) BLLs and percentages of BLLs >= 5.0 mu g/dL in Period I: 25 April 2006 to 15 October 2007 (earliest timeframe available for study) and Period II: 25 April 2012 to 15 October 2013 (timeframe immediately before the water switch), were compared to Period III, 25 April 2014 to 15 October 2015 (FRW exposure). Results: There were 5663 BLLs available for study. GM +/- SE BLLs decreased from 2.19 +/- 0.03 mu g/dL in Period I to 1.47 +/- 0.02 mu g/dL in Period II [95% CI, 0.64, 0.79]; pdecreased further to 1.32 +/- 0.02 mu g/dL during the FRW Period III [95% CI, 0.79, 0.95]; p<.001. The percentage of BLLs >= 5.0 mu g/dL decreased from Period I (10.6%) to Period II (3.3%) [95% CI, 5.7, 8.8]; p<.001 and from Period I to Period III (3.9%) [95% CI, 5.0, 8.2]; p=.002. The 0.6% increase from Period II to Period III was not statistically significant [95% CI, -1.9, 0.57]; p=.30. Conclusion: Analyses of GM and percentages >= 5.0 mu g/dL of BLLs do not support the occurrence of a global increase in BLLs in young children of Flint during the entire 18-month period of FRW exposure.