Survey of ²²⁶ Ra / ²²⁸ Ra and inorganic constituents in Iowa private drinking water wells

Abstract Radium is a naturally‐occurring radioactive element found in Upper Midwest aquifers, yet exposure risks for unregulated water sources in this region are unknown. A survey of 226/228 Ra and other inorganic constituents in 94 private wells was conducted in 2019 across 10 Iowa counties. Within private wells, 53% measured below minimum detectable activity whereas 6.3% have 226/228 Ra levels above the United States Environmental Protection Agency Maximum Contaminant Level. 226/228 Ra occurrence was not associated with well‐depth or chemical surrogates, but were generally consistent with the lithology and historical water quality trends for aquifers. In 2020, 11 of the 226/228 Ra‐impacted wells were re‐sampled to assess the efficacy of in‐home water treatment. Water softeners reduced 226/228 Ra to non‐detectable activities, but other inorganic constituents persisted and their removal required more advanced treatment. This study suggests that 226/228 Ra occurrence in private wells can reasonably be anticipated from public water supply data if reliable information is available to identify the source aquifer.