Estimating Lithium Concentrations in Groundwater Used as Drinking Water for the Conterminous United States

Abstract

Lithium (Li) concentrations in drinking-water supplies are not regulated in the United States; however, Li is included in the 2022 U.S. Environmental Protection Agency list of unregulated contaminants for monitoring by public water systems. Li is used pharmaceutically to treat bipolar disorder, and studies have linked its occurrence in drinking water to human-health outcomes. An extreme gradient boosting model was developed to estimate geogenic Li in drinking-water supply wells throughout the conterminous United States. The model was trained using Li measurements from ∼13,500 wells and predictor variables related to its natural occurrence in groundwater. The model predicts the probability of Li in four concentration classifications, ≤4 μg/L, >4 to ≤10 μg/L, >10 to ≤30 μg/L, and >30 μg/L. Model predictions were evaluated using wells held out from model training and with new data and have an accuracy of 47−65%. Important predictor variables include average annual precipitation, well depth, and soil geochemistry. Model predictions were mapped at a spatial resolution of 1 km 2 and represent well depths associated with publicand private-supply wells. This model was developed by hydrologists and public-health researchers to estimate Li exposure from drinking water and compare to national-scale human-health data for a better understanding of dose−response to low (<30 μg/L) concentrations of Li.

Lithium Pollution and Its Associated Health Risks in the Largest Lithium Extraction Industrial Area in China

“…Due to its high mobility, , Li from anthropogenic sources can easily spread in the environment and thus has a large chance of affecting microorganisms, plants, animals, and humans in broader areas. However, the biological and metabolic effects of high Li concentrations on aquatic and terrestrial ecosystems are still not well-understood and remain to be investigated in future studies.…”

“…As an emerging and potentially toxic element, Li has been found to be widely distributed in various environmental media, including air, water, and soil. − It poses potential harm to microorganisms, plants, animals, and humans when present in environmentally relevant concentrations. − For example, recent research found that even environmentally relevant concentrations of Li can have significant effects on plant development (e.g., soybean) through metabolic reprogramming. , Additionally, Li has been found to reduce the growth and reproduction of zooplankton (e.g., Daphnia magna) and cause oxidative damage to invertebrates (e.g., earthworm). − Furthermore, the presence of Li in drinking water can impact human health by inducing abnormalities and dysfunctions through multiple metabolic pathways. − The US Environmental Protection Agency (US EPA) has proposed a provisional reference dose ( p -RfD) of 2 μg kg –1 day –1 and a health-based screening level of 10 μg/L for Li in drinking water. , To regulate the exposure to Li, the Eurasian Economic Union has established a limit of 30 μg/L for Li levels in packaged drinking water, including natural mineral water . Furthermore, there have been widespread reports on the toxicity of other associated toxic elements such as F, Rb, Cs, Zn, and Tl. ,− Considering their potential toxicity and health effects, it is crucial to investigate the impact of Li extraction activities on the levels of Li and associated components in the environment.…”