The geologic profile of the western United States lends itself to naturally elevated levels of arsenic and uranium in ground water, which frequently exceeds the EPA limit of 10 parts per billion (ppb) for arsenic and 30 ppb for uranium. Mining can exacerbate this problem by introducing waste high in arsenic and uranium into groundwater systems. This study focuses on quantification of these two contaminants in unregulated water sources on the Navajo and Hopi reservations. Of specific concern to these communities are the health effects associated with chronic exposure to arsenic and uranium in their water. Unfortunately, current water maps lack updated and reliable information on the extent of contamination on these reservations.  In this study, water samples were collected from over 100 wells in the western area of the Navajo reservation and in various locations of the Hopi reservation.  Samples were collected in the winter, spring, and summer seasons in 2014.  Due to low concentrations of arsenic and uranium in the water, all samples were analyzed via inductively coupled plasma mass spectrometry (ICP-MS) which allows for accurate determination of the elements at concentrations greater than or equal to 0.1 ppb. Preliminary results determined a number of wells exceed the EPA drinking water standard for both arsenic and uranium, some of which are the primary water source for communities.  This updated water quality information can provide communities with the knowledge needed to create action plans which mitigate exposure. We acknowledge the National Institutes of Health sources for funding and supporting this work.

Quantification of arsenic and uranium in unregulated water sources on the Navajo and Hopi reservations

249th National Meeting (2015)

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