Lithium Occurrence: What We Have Learned from UCMR5

Drinking Water
Oral Presentation

Prepared by Y. Li
Eurofins Eaton Analytical, LLC, 110 South Hill Street, South Bend, IN, 46617, United States


Contact Information: [email protected]; 574-707-5026

ABSTRACT

Lithium (Li) is a naturally occurring alkali metal widely and geographically found in minerals, groundwater, and surface water. The U.S. Environmental Protection Agency (EPA) has not regulated or published a health advisory (HA) level for Li in drinking water. However, EPA has adopted the non-enforceable Health Reference Level (HRL) of 10 µg/L developed by the U.S. Geological Survey (USGS) for the purposes of screening Li in drinking water. Historically, Li contamination was studied in groundwater. Some researchers even reported that Li was detected in nearly 100% of the studied groundwater samples. A few recent studies also reported that 30‒50% of groundwater samples could have detections for Li near or above the HRL of 10 µg/L.

The fifth Unregulated Contaminant Monitoring Rule (UCMR5) has included Li as one of the 30 contaminants monitored during 2023‒2025. UCMR5 will quantify and characterize the occurrence of geogenic Li in drinking water using groundwater or surface water as the source, at the national scale. UCMR5 will analyze Li in 70,000‒80,000 samples collected from approximately 10,310 public water systems (PWS) with a minimum reporting level (MRL) of 9 µg/L. To date, 28.4% of the results and 33.9% of the PWS have detected Li at concentration levels of ≥ the MRL, 20.1% of the results and 24.6% of the PWS have detected Li at concentration levels of > the HRL

This work will provide the latest UCMR5 outcomes through data mining of the National Contaminant Occurrence Database (NCOD). The Li contaminant occurrence at both the national and geographical state levels will be included. This presentation will also describe various challenges experienced in our laboratories and the solutions implemented to resolve those issues. It is our expectation that this presentation will be helpful in implementing UCMR5, understanding the widespread occurrence of Li contamination in drinking water supplies, planning and executing appropriate Li control and remediation actions, and establishing future drinking water Li regulations.