Native American communities face higher exposure to toxic metals compared to the general U.S. population. These issues are especially important as new mining projects, particularly for lithium mining, are being explored near Tribal Lands. According to the U.S. Geological Survey, nearly half of public-water supply and over a third of private wells have lithium concentrations that could be harmful. Our study aims to understand how much lithium participants in the Strong Heart Study (SHS) have been exposed to and whether drinking water is the main source. To do this, we measured urinary lithium concentrations from SHS participants collected during Phase 5 (2006-2009) and Phase 7 (2022-2023). We also measured lithium concentrations in tap water from participants' homes during Phase 7. By comparing lithium levels in urine and water, we aim to understand how environmental changes affect exposure. If drinking water is a key source of lithium, our findings can help guide future protections for safer water in Native communities.