Groundwater chemistry may raise children’s lead exposure risk

A nationwide county-level study reveals how subtle differences in groundwater chemistry may influence pipe corrosion and children’s blood lead levels, highlighting the hidden role of water treatment and infrastructure in protecting vulnerable communities.

Study: Groundwater Chemistry and Children’s Blood Lead Levels: A County-Wise Analysis in the United States. Image credit: BestPhotoStudio/Shutterstock.com

Regular groundwater monitoring is essential to protect children in vulnerable communities, where mineral content and pH levels may corrode older pipes and contaminate drinking water with lead. A recent study in GeoHealth examined county-level associations between groundwater chemicals and children’s blood lead levels.

Lead exposure increases health risks in children

Lead was widely used in late-19th-century US infrastructure, from water distribution pipes to paint. Despite well-documented health risks, the US did not ban lead paint until 1978 or lead plumbing until 1986. Even after these bans, existing lead pipes remained in use; an estimated 9.2 million are still in use nationwide.

When groundwater has low pH or low mineral content, it can corrode pipes and contaminate drinking water with lead. To address this, the EPA established the Lead and Copper Rule, requiring monitoring and corrective action when lead concentrations exceed 15 μg/L. In October 2024, the rule was strengthened to mandate replacing most lead pipes within 10 years and to lower the action level to 10 μg/L. However, federal funding remains insufficient to meet national replacement needs, which may delay compliance and prolong exposure risks.

Approximately 590,000 US children aged 1 to 6 had elevated blood lead levels in 2016. Previous studies have shown that children absorb more lead than adults do. Even low-level exposure causes lower IQs, poor motor skills and memory, attention deficits, decreased brain volume, and, in severe cases, brain damage. It must be noted that no amount of lead exposure is safe.

Lead exposure disproportionately affects minority and low-income communities living in older housing. Non-Hispanic Black children are 2.8 times more likely to have elevated blood lead levels than white children. Children using private groundwater wells are at higher risk, as these unregulated wells may contain higher lead levels without proper testing and are not covered by federal drinking water regulations.

Groundwater chemistry and childhood lead exposure

Low pH and decreased concentrations of groundwater metals, such as calcium, magnesium, iron, and sodium, increase water corrosiveness, leading to greater lead intake from corroded pipes. Although multiple studies have shown that groundwater chemistry affects lead exposure, the association between local water conditions and socioeconomic factors remains unclear. Identifying key chemicals can help develop targeted interventions in affected communities.

The current study integrated data from multiple sources to investigate the relationship between 30 groundwater chemical concentrations and the prevalence of elevated blood lead levels in children across 1,104 counties in 22 US states relying on groundwater as a public drinking water source.

County-level water source data were obtained from the CDC‘s Water Fluoridation Reporting System. Lead exposure data for children below 72 months (2012–2017) were sourced from the CDC‘s Childhood Lead State Surveillance Data. Groundwater quality data were obtained from the USGS Geochemical Database, which contains chemical data from 124,000 wells (1901–2013).

Groundwater chemistry was examined as an upstream driver of pipe corrosion and lead mobilization, rather than as a direct measure of tap water exposure, recognizing that utilities routinely modify water chemistry through treatment. County-level covariates from the 2021 American Community Survey included the unemployment rate, median household income, the percentage of adults with less than a high school education, and the percentage of children aged 0–17 in poverty.

Key findings and implications

Analytical data revealed median values for selected groundwater chemicals, including pH 7.3, alkalinity 206 mg/L, bicarbonate 243 mg/L, dissolved oxygen 3.1 mg/L, total dissolved solids 360 mg/L, selenium 0.5 μg/L, copper 2 μg/L, and arsenic 1 mg/L as reported in the study.

Higher groundwater concentrations of arsenic, copper, dissolved oxygen, and selenium were significantly associated with elevated blood lead levels in children in the primary weighted regression analysis. In contrast, pH, calcium, iron, and bicarbonate exhibited smaller, non-significant decreases.

Groundwater lead itself was not significantly associated with blood lead levels. The majority of tested ions showed no significant associations. County-level mean concentrations of calcium, iron, and lead were associated with lower blood lead levels in some sensitivity analyses.

Bayesian Kernel Machine Regression analysis found that calcium, lithium, and alkalinity had high posterior inclusion probabilities but minimal estimated effects on childhood blood lead levels. Selenium showed a moderate inclusion probability with a near-zero effect estimate. Sensitivity analyses indicated inconsistent results for ions that were significant in the main analyses, while non-significant ions remained consistent.

After imputing missing values, pH increases were associated with lower blood lead levels. Groundwater iron and lead concentrations were associated with reductions in blood lead levels in most analyses. Most chemicals showed negligible effects with no statistical significance.

Groundwater chemistry matters

Groundwater chemistry was associated with childhood lead exposure at the county level, though the magnitude and direction of some associations depended on how missing blood lead data were handled.

Higher concentrations of arsenic, copper, dissolved oxygen, and selenium were associated with elevated blood lead levels in the primary analysis, with selenium showing the strongest effect. Traditional protective indicators, such as pH, alkalinity, and calcium, showed inconsistent associations across models.

Groundwater lead itself was not significantly associated with blood lead levels, which the authors suggest may reflect water treatment practices and corrosion dynamics that decouple source-water lead from tap-water exposure. As an ecological analysis, the findings do not imply individual-level risk.

These results highlight the need for regular groundwater monitoring in vulnerable communities alongside targeted corrosion control and treatment strategies, and for interventions targeting areas with elevated levels of corrosion-promoting hydrogeochemical conditions, while underscoring the importance of cautious interpretation.

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