Children's Lead Exposure: A Multimedia Modeling Analysis to Guide Public Health Decision-Making

Abstract

Background: Drinking water and other sources for lead are the subject of public health concerns around the Flint, Michigan, drinking water and East Chicago, Indiana, lead in soil crises. In 2015, the U.S. Environmental Protection Agency (EPA)'s National Drinking Water Advisory Council (NDWAC) recommended establishment of a "health-based, household action level" for lead in drinking water based on children's exposure.

Objectives: The primary objective was to develop a coupled exposure-dose modeling approach that can be used to determine what drinking water lead concentrations keep children's blood lead levels (BLLs) below specified values, considering exposures from water, soil, dust, food, and air. Related objectives were to evaluate the coupled model estimates using real-world blood lead data, to quantify relative contributions by the various media, and to identify key model inputs.

Methods: A modeling approach using the EPA's Stochastic Human Exposure and Dose Simulation (SHEDS)-Multimedia and Integrated Exposure Uptake and Biokinetic (IEUBK) models was developed using available data. This analysis for the U.S. population of young children probabilistically simulated multimedia exposures and estimated relative contributions of media to BLLs across all population percentiles for several age groups.

Results: Modeled BLLs compared well with nationally representative BLLs (0-23% relative error). Analyses revealed relative importance of soil and dust ingestion exposure pathways and associated Pb intake rates; water ingestion was also a main pathway, especially for infants.

Conclusions: This methodology advances scientific understanding of the relationship between lead concentrations in drinking water and BLLs in children. It can guide national health-based benchmarks for lead and related community public health decisions. https://doi.org/10.1289/EHP1605.

Figure 1.

Illustration of Stochastic Human Exposure and Dose Simulation (SHEDS)–Integrated Exposure Uptake and Biokinetic (IEUBK) modeling to inform a health-based benchmark for Pb.

Figure 2.

Evaluation of Stochastic Human Exposure and Dose Simulation (SHEDS)–Integrated Exposure Uptake and Biokinetic (IEUBK) modeled blood lead levels (BLL) vs. National Health and Nutrition Examination Survey (NHANES) 2009–2014 BLL for different age groups. conc., concentration.

Figure 3.

Estimated contribution of exposure pathways to BLL, for national scale. Bar charts provide Pb daily exposure contributions from diet, soil and dust ingestion, water, and inhalation from air for percentiles of the BLL distribution. The bars are 10% increments in the BLL distribution. The median BLL for each increment is indicated under each bar. Exposure in the figure is adjusted for bioavailability of Pb in each exposure pathway. Panel (A), national scale for 0- to 6-mo-olds; Panel (B), national scale for 1- to $<2-\mathrm{y}$-olds.

Figure 4.

Illustrative graphs for determining household tap water Pb concentrations were calculated for different scenarios. y-Axis is modeled blood Pb level at 97.5th percentile of simulated population; x-axis is daily average water Pb concentration. The different colored lines represent different ages: orange is infants age 0–6 mo, dark blue is 1- to $<2-\mathrm{y}$-olds, and light blue is 2- to $<6-\mathrm{y}$-olds.