LAUSR

More than 40% of the U.S. public water supply comes from groundwater.1 In the semiarid southwestern United States, where surface water can be scarce and drought conditions make these sources unreliable, groundwater is an important source of drinking water for many people. For example, in northeastern Arizona, groundwater delivers up to 60% of the public water supply.2 In sparsely populated areas where the cost-to-benefit ratio makes it challenging to develop water infrastructure,3 unregulated wells and springs are important water sources.4 However, these sources carry a heavy risk of contamination. Tribal lands are especially affected by the risk of drinking contaminated water, and in many cases testing is absent altogether, as Mok et al. write in this issue of Environmental Health Perspectives.5 The Navajo Nation is a case in point of the water-related challenges faced by Tribes. Nearly half of the 300,000 members of the Navajo Tribe live on the Reservation,6 which spreads over parts of Arizona, New Mexico, and Utah. The Navajo Nation has one of the world’s largest uranium reserves on its lands.7 More than 500 abandoned uranium mine claims have created human health and environmental concerns on Navajo lands,8 and our team reported that many unregulated water sources on the Navajo Nation have elevated levels of arsenic, uranium, manganese, and other elements from former mining operations.9,10 Although mining-related contamination is one of the betterknown problems in Navajo water, other drinking water contaminants, such as perand polyfluoroalkyl substances (PFAS), are understudied on Tribal lands, as Mok et al. point out.5 Municipal wells on the Navajo Nation are regulated by the Navajo Tribal Utility Authority (www.ntua.com). However, the reliance on unregulated water sources on Navajo lands for household use, including drinking water, makes PFAS and other emerging contaminants increasingly important as a potential health risk to the Navajo people, especially because the increase in wildfires, trash burning, and other potential sources of these compounds makes their presence in water sources likely.11,12 The dangers of unregulated water sources are especially relevant to the estimated 70,000 people on the Navajo Nation who lack running water in their homes.13 Those without access to public water systems must haul water from unregulated sources.14 Unregulated wells are prone to contamination issues because they may not be as deep or as well-constructed as municipal wells.15 Also, unregulated wells are not regularly tested for contaminants and often lack water treatment systems.16 Sovereignty is especially important to Native Americans when it comes to Tribal management of drinking water and other resources. Sovereignty provided Tribes with water rights at the time their reservations were established. These rights are based on the 1908 Supreme Court decision in Winters v. United States (the Winters Doctrine), which guaranteed that land established as a reservation would be permanently owned by the Tribe. Further, it guaranteed rights to adequate amounts of water to meet the needs of the reservation. The Winters Doctrine has been essential in negotiations between Tribes and other water users. For example, Tribes have successfully leased their water rights to nontribal entities, which has provided an important source of revenue.17 However, this practice is controversial among stakeholders, including Tribal communities, especially in western states where non-Native water users have historically used Tribal water for free.17 Navajo sovereignty also came into play in 2005 when the Tribe banned uranium mining with the Diné Natural Resources Protection Act (DNRPA) of 2005.18 The DNRPA was enacted to ensure that no further harm will be caused from uranium mining. The act highlights the importance of protecting the natural environment for cultural and spiritual reasons. It further states that a healthy physical and mental environment is the right of all Navajo people. In this way, it aligns with the Fundamental Laws of the Diné, Navajo traditional beliefs that provide the foundation for addressing the complex relationship between nature and humans.20 These Laws, which have played a role in Tribal life for many generations, were codified in 2002 and directed by the Navajo Nation Council (2002) to be incorporated into Tribal selfgovernance.19 The connections that the DNRPA provides among laws, culture, and environmental protection establishes a framework to create other socially appropriate legislation that not only safeguards resources such as drinking water but also considers Navajo principles and sovereignty.20 Often, environmental policy is developed for issues facing Tribes without input from those Tribes. However, Tribes should have the opportunity to address environmental issues using traditional ecological knowledge in accordance with the Navajo Fundamental Laws. It is essential that these Laws are used today and into the future to provide the basis for Navajo decision making.