The biotic exposure and uptake of radionuclides and potential health effects due to breccia pipe uranium mining in the Grand Canyon watershed are largely unknown. This paper describes the use of the RESRAD-BIOTA dose model to assess exposure of small rodents (n = 11) sampled at three uranium mine sites in different stages of ore production (active and postproduction). Rodent tissue and soil concentrations of naturally occurring uranium (234U, 235U, and 238U), thorium (228Th, 230Th, and 232Th), and radium (226Ra) radioisotopes were used in the dose model. The dose assessment results indicated that the potential internal, external, and total doses to rodents were below the US Department of Energy’s biota dose standard of 1 mGy d−1. As expected, tissue concentrations of 238U, 234U, and 230Th were in approximate equilibrium; however, 226Ra results in tissue were 1.25 to 5.75 times greater than 238U, 234U, and 230Th tissue results for 10 out of 11 samples. Soil at the three sites also displayed 226Ra enrichment, so it is likely that the 226Ra enrichment in the rodents was from soil via typical activities (i.e., burrowing, incidental ingestion, bathing, etc.) or by dietary uptake of translocated 226Ra. The results suggest that 226Ra is more mobile in this environment and bioaccumulates in these rodent species (e.g., in bones via the bloodstream). Internal dose accounting suggests that 226Ra is the radionuclide of most concern for rodent exposure and health.
1Savannah River National Laboratory, Savannah River Site, Aiken, SC;
2US Geological Survey, Columbia Environmental Research Center, Columbia, MO.
The authors declare no conflicts of interest.
For correspondence contact Tim Jannik, Savannah River National Laboratory, Savannah River Site, Aiken, SC, 29808, or email at firstname.lastname@example.org.
(Manuscript accepted 24 October 2018)
Online date: March 19, 2019