The Navajo Nation has been experiencing a water crisis for generations. Over the past three decades, severe drought conditions have significantly reduced the amount of rainfall and dried up lakes and ponds [1]. Approximately 90% of the water currently used by the Navajo Nation is groundwater. However, much of this groundwater is undrinkable due to severe contamination above safe drinking levels from uranium and arsenic. This contamination is partially caused by a history of uranium mining by the US government. Approximately 25% of all uranium that exists in the US is found in the Navajo Nation, and the US government monopolized the purchase and mining of uranium within the Navajo Nation from the 1940s to early 1960s. The mining contaminated water, food, and the land, causing widespread sickness and mutations due to radiation. Health risks are correlated with uranium exposure, including higher rates of kidney cancer among the Navajo Nation people [2].
Figure 1 shows the locations of the proximity of major cities, wells, and abandoned uranium mines within the Navajo Nation [3]
Arsenic is also known to be a common contaminant in the region around the Navajo nation. Arsenic deposits can be found in layers of sedimentary rock in the Colorado Plateau where the Navajo Nation is located, and can easily contaminate the groundwater supply. Long term exposure to arsenic is known to cause cancer and skin lesions and have negative impacts in the cognitive developments of children and young adults [4].
Sites of past mining activities also contain high levels of dissolved metals due to acid rock drainage. This occurs because mining activity increases water acidity, as pyrite and other sulfide minerals react with the oxygen in water sources, increasing the concentration of dissolved metals in the water [2].
Figure 2 shows a map of areas with high levels of arsenic (above) and uranium (below) contamination. 10 μg/L is the maximum contaminant level (MCL) for arsenic, and 30 μg/L is the MCL for uranium [5].
Most of this contaminated water comes from sources like private wells, which are not regulated by government agencies and are prone to contamination issues due to contaminants from mining and other sources that accumulate at their shallower depths [2]. In the Navajo Nation, these private wells are typically reserved for livestock use. However, 30% of homes lack access to municipal water supplies and are required to drive long distances and haul water to their homes at hefty prices due to high gas and equipment costs. Due to the inconvenience of obtaining drinking water, these families may resort to using water from these wells for drinking purposes despite their high levels of contamination. In addition to uranium and arsenic, there are also excess levels of vanadium, calcium, manganese, and lithium in these private wells, which can be toxic at high concentrations [6].
Filtering the contaminants in their water supplies is essential for supplying safe drinking water and agricultural purposes. Water for agricultural purposes does not need to be filtered to the extent of drinking water, but harmful minerals like uranium and arsenic in unfiltered water can still be incorporated into the food supply of the Navajo Nation through agriculture. Thus, cheaper but less efficient filtration methods like the Kanchan Arsenic Filter could filter water for agricultural purposes while expensive but efficient methods like the Reverse Osmosis system could filter drinking water.
To address the issue of water contamination in water sources near Navajo Nation schools, our booklet may include instructions and information about various types of filtration systems, water quality testing, and water collection. Some methods are more friendly to be taught as a hands-on activity for students like testing water quality and building the Biosand Filter, while others like the Reverse Osmosis system may be installed into the school to facilitate teaching of agricultural methods through the small school garden and to provide safe drinking water. Different methods are explored through various benefits and limitations to give students the necessary context to choose which method would work best for them when they transition into sustainable agriculture.
Works Cited:
[1] Navajo Nation continues to experience drought. (n.d.). Navajo-Hopi Observer News. https://www.nhonews.com/news/2021/oct/12/navajo-nation-continues-experience-drought/
[2] Ingram, J. C., Jones, L., Credo, J., & Rock, T. (2020, May). Uranium and arsenic unregulated water issues on Navajo Lands. Journal of vacuum science & technology. A, Vacuum, surfaces, and films : an official journal of the American Vacuum Society. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7083651/
[3] US EPA, R. 09. (2016, February 16). Abandoned Mines Cleanup. US EPA. https://www.epa.gov/navajo-nation-uranium-cleanup/abandoned-mines-cleanup
[4] World Health Organization. (2018, February 15). Arsenic. Who.int; World Health Organization: WHO. https://www.who.int/news-room/fact-sheets/detail/arsenic
[5] Hoover, J., Gonzales, M., Shuey, C., Barney, Y., & Lewis, J. (2016). Elevated Arsenic and Uranium Concentrations in Unregulated Water Sources on the Navajo Nation, USA. Exposure and Health, 9(2), 113–124. https://doi.org/10.1007/s12403-016-0226-6
[6] Bourzac, K. (2019, August 28). Arsenic and other metals contaminate Navajo Nation and Alaska Native wells. C&en. https://cen.acs.org/content/cen/articles/97/web/2019/08/Arsenic-metals-contaminate-Navajo-Nation.html