A new study published in the journal GeoHealth shows that the chemical composition of groundwater may be an important factor increasing the risk of lead exposure in children, even in areas where tap water is treated.

The researchers analyzed data from 1,104 counties in 22 U.S. states that rely on groundwater sources for drinking water and compared them with data on groundwater chemistry and blood lead levels in children under the age of six.

This geo-environmental assessment highlights that not only the concentration of lead itself, but also its interaction with other elements and water parameters, can influence the risk of harmful exposure. The study found that low pH levels and reduced concentrations of certain minerals (calcium, magnesium, iron, and sodium) make water more corrosive, increasing corrosion of old water pipes and facilitating the leaching of lead into drinking water. According to the authors, these effects may be amplified in aging water systems with a high proportion of outdated lead pipes.

The analysis also revealed that elevated concentrations of arsenic, copper, dissolved oxygen, and selenium in groundwater were significantly associated with higher blood lead levels in children at the county level, with selenium showing the strongest effect.

This suggests that groundwater composition may act as a “hidden” factor influencing the severity and prevalence of lead exposure.

The authors emphasize that lead concentrations in groundwater alone were not directly associated with elevated blood lead levels in the analysis, which may reflect water treatment practices and complex corrosion mechanisms that decouple the source from actual exposure.

Experts remind that there is no safe level of lead in children’s blood, and early exposure can lead to serious consequences for the nervous system, cognitive development, memory, and behavior.