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TOPLINE:

Increased lithium exposure in drinking groundwater was associated with a reduced risk for cancer, according to findings from a US study. The protective effect was observed across different cancer types, sexes, and geographic regions.

METHODOLOGY:

• Lithium is not currently regulated in drinking water in the United States, though it is listed on the Environmental Protection Agency’s contaminant candidate list. While studies suggest that lithium treatment may lower the risk for cancer in patients with bipolar disorder, the impact of lithium on cancer risk in the general population remains unclear.
• Researchers conducted a nationwide epidemiologic study, which included 252,178 individuals without a history of cancer, to explore the association between lithium exposure in drinking groundwater across and cancer risk in the general population.
• Researchers assigned lithium exposure for each participant based on the three-digit zip code of their residential address, using Geological Survey data from 4700 wells across the United States.
• Estimated lithium exposure was categorized into five quintiles: Quintile 1 (1.3-3.6 μg/L), quintile 2 (3.7-6.1 μg/L), quintile 3 (6.2-7.2 μg/L), quintile 4 (7.3-25.5 μg/L), and quintile 5 (25.6-149.9 μg/L). The median lithium exposure was 7.0 μg/L, and the median follow-up duration was 3.6 years.
• The primary outcome was cancer diagnosis.

TAKEAWAY:

• Overall, higher lithium exposure in drinking groundwater was associated with lower cancer risk. In total, 7573 cancer cases were detected. Compared with people in the lowest exposure group, the risk for cancer was lower among participants in the second (hazard ratio [HR], 0.43), third (HR, 0.63), fourth (HR, 0.49) and fifth (HR, 0.29) quintiles.
• This lower risk was observed across a range of cancer types, including breast cancer (HR, 0.16 for highest vs lowest quintile), prostate cancer (HR, 0.15), bladder cancer (HR, 0.11), colorectal cancer (HR, 0.18), kidney cancer (HR, 0.14), leukemia (HR, 0.22), non-Hodgkin lymphoma (HR, 0.14), central nervous system cancer (HR, 0.10), and thyroid cancer (HR, 0.10). These associations remained significant in long-term residents, except for leukemia.
• The association persisted in both men (HR, 0.17) and women (HR, 0.13).
• Western states had a much higher lithium concentration in groundwater (median, 43.2 vs 5.7 μg/L) and had lower cancer risks than eastern states (though reduced cancer risks were observed in both regions).

IN PRACTICE:

“Higher lithium exposure in drinking groundwater was associated with reduced cancer risk in the US general population both for cancer overall and for specific cancer types,” the authors wrote. However, they cautioned “this study do not necessarily promote intake of lithium-rich water as a public health strategy” as the broader health implications of environmental lithium exposure remain unclear and warrant further research.

SOURCE:

The study, led by Jiajun Luo, PhD, MPH, Biological Science Division, The University of Chicago, Chicago, was published online in JAMA Network Open.

LIMITATIONS:

The accuracy of exposure assessment was limited by misclassification bias and the use of kriging, which may not have fully accounted for subtle geographic variations, weather factors, and human activities influencing actual lithium exposure levels. Data on detailed cancer characteristics such as staging and lymph node status could not be obtained, preventing the investigation of underlying mechanisms. The study also lacked information on bottled water consumption, potentially affecting the accuracy of exposure assessment. Other groundwater contaminants that could influence risk estimates were not considered.

DISCLOSURES:

The research was supported by grants from the National Institutes of Health. One author disclosed serving on a speaker’s bureau for Regeneron/Sanofi and Optinose and acting as the site principal investigator for clinical trials by Upstream Bio and Lyra during the study. No other disclosures were reported.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.