Eligibility criteria
To be eligible for participation in the SHWS, households had to be located in a Great Plains Nation, have at least one American Indian household member residing in the home, and utilize a private well for drinking and cooking with an arsenic concentration > 10 μg/L and uranium concentrations < 30 μg/L. Uranium contamination below the EPA MCL for uranium was included because the arsenic filters provided by the SHWS do not remove uranium (30 μg/L) [