The USGS study collected data representative of groundwater used as a source of drinking water at the national- and regional-aquifer scale.
The U.S. Geological Survey (USGS) reported on a new study on Feb. 11.
The survey report shows approximately 45% of U.S. public-supply wells and about 37% of domestic-supply wells have concentrations of lithium.
The USGS compiled data for lithium measured in untreated groundwater from 1,464 public-supply wells and 1,676 domestic-supply wells between 1991 and 2018, reported the NGWA.
The study aimed to collect data representative of groundwater used as a source of drinking water at the national- and regional-aquifer scale, according to USGS. Groundwater in the aquifers sampled represents 80% of groundwater used for public supply in the country and is a source of drinking water for about 100 million people, according to the report.
Lithium was added to the EPA's proposed Unregulated Contaminant Monitoring Rule in January 2021, reported USGS.
The concentrations were highest in arid regions and older groundwater, or groundwater that recharged the aquifer before 1953, according to the report. The lowest concentrations were in carbonate-rock aquifers and the most elevated lithium concentrations were measured in wells that tap unconsolidated clastic aquifers in the western U.S., added the report.
The USGS collaborated with the U.S. EPA to calculate a nonregulatory health-based screening level for drinking water of 10 micrograms per liter (µg/L) or parts per billion (ppb) as context for evaluating lithium concentrations.
According to USGS, some key points of the survey report are:
- Lithium in groundwater has not been comprehensively evaluated in the US;
- Concentrations in groundwater frequently exceed the human-health benchmark;
- The distribution of lithium concentrations varies widely by lithology and climate;
- Higher lithium concentrations are found in arid regions and older groundwater; and
- Cation exchanges or mixing with saline water lead to highest concentrations.
The full study can be read here.