Groundwater Chemistry and Children's Blood Lead Levels: A County-Wise Analysis in the United States

Groundwater is a major source of drinking water in the United States (US). Groundwater chemistry can contribute to lead leaching from water supply pipes due to factors such as pH and mineral content that influence corrosion. Lead exposure disproportionately affects children from low-income neighborhoods. We evaluated the association of county-level groundwater chemicals with the percentage of children with blood lead levels >5 μg/dL (BLL5%) in 1,104 US counties served by public water utilities using groundwater. Out of the 4,844 BLL5% observations, 3,525 had values of "NA" for BLL5%. We used weighted least squares regression to evaluate the associations, adjusting for covariates such as county-level median household income, educational attainment, and poverty rates. Bayesian Kernel Machine Regression (BKMR) was used to assess the joint effects of all chemicals on BLL5%. Sensitivity analyses tested the robustness of our results by imputing missing BLL5% values. A one mg/L increase in arsenic, copper, dissolved oxygen, and selenium was associated with increases in BLL5% of 0.0512% (95% CI: 0.0002%, 0.1023%), 0.0358% (95% CI: 0.0208%, 0.0508%), 0.0956% (95% CI: 0.0225%, 0.1687%), and 0.3038% (95% CI: 0.1747%, 0.4420%), respectively. Alkalinity, pH, calcium, bicarbonate, and dissolved solids were not found to be statistically significant. BKMR identified calcium, lithium, and alkalinity (posterior inclusion probabilities = 1,000) as important, though with minimal effects. Sensitivity analyses showed variability in results depending on assumptions about missing data. Our findings highlight the importance of monitoring groundwater quality and implementing interventions to reduce childhood lead exposure risks in vulnerable populations, particularly minority, and low-income children.