Assessing potential risks from exposure to natural uranium in well water

Over 50% of the wells in the Nambe region of northern New Mexico exceed the US Environmental Protection Agencyʹs recommended drinking water standard of 20 μg l−1 for 238U; the highest in the area was measured at 1200 μg U l−1. Uranium uptake was estimated in tomato (Lycopersicon esculentum), squash (Cucurbita pepo), lettuce (Lactuca scarriola), and radish (Raphanus sativus) irrigated with Nambe well water containing <1, 150, 500, and 1200 μg U l−1. Plant uptake and human dose and toxicity associated with ingestion of water and produce and inhalation of irrigated soil related to gardening activities were evaluated. Uranium concentration in plants increased linearly with increasing U concentration in irrigation water, particularly in lettuce and radish. The estimated total committed effective dose for 70 years of maximum continuous exposure, via the three pathways to well water containing 1200 μg U l−1, was 0.17 mSv with a corresponding kidney concentration of 0.8 μg U g−1 kidney.