Science for Decision Making on Uranium Mining in Arizona

Exposure Characterization in Plants and Animals through the Mine Life Cycle

At Pinyon Plain (formerly Canyon) Mine

Pinyon Plain (formerly Canyon) Mine Life Cycle

The Pinyon Plain (formerly Canyon) mine represents premining conditions during the development of the mine.

Vegetation, terrestrial invertebrates, and small rodents were collected for chemical and radiological exposure characterization at

  • Arizona 1 Mine and reference areas in the summer of 2015 (before reclamation ).1
  • Pinenut Mine and reference areas in the summer of 2015 (during active mining).1
  • Pinyon Plain (formerly Canyon) Mine in the summer of 2013 (before mining).2
  • EZ breccia pipes in the summer of 2015 (vegetation only; known uranium-mineralized but undeveloped breccia pipes).
  • Kanab North Mine in 2015 (decades after mining, before reclamation).3


  • We used traditional and new survey tools to understand how mining activities can affect local food webs. Chemicals can enter animals by ingestion, inhalation, absorption, and dietary transfer.1,2,3,4,5,6,7,8
  • Plants and animals take up mining-related radionuclides, uranium, other elements but direct effects were not linked.1,2,3
  • Radiation levels in plants and animals were low. Radiation enters rodents through soil interactions (burrowing, incidental ingestion, bathing, etc.) or their diet. Radium-226 was below protective levels. It is of most concern for rodent health.2,3,8
  • Tadpoles in the mine pond accumulated mining-related chemicals. Arsenic and selenium levels exceed protective thresholds.2

Pinyon Plain (formerly Canyon) Mine Activities

This study establishes the only pre-mining concentration data available for biota at uranium mines within the Grand Canyon watershed, which is essential for examining the potential effects of mining in this internationally recognized landscape.

  • Radiation levels were low.
  • Gross alpha levels were below the reporting limit in all samples.
  • Gross beta levels were indicative of background in vegetation and rodents.

Constituents other than uranium can pose risks to biota at uranium mines. However, chemical concentrations in rodents and terrestrial invertebrates indicate that surface disturbance during mine construction has not resulted in statistically significant spatial differences in fauna concentrations adjacent to the mine.4

  • Aeolian transport and loading of uranium, thallium, lead, nickel, copper and arsenic are occurring off-site (downwind of the mine).
  • Chemical concentrations in egg contents and nestlings of non-aquatic birds were less than method quantification limits or did not exceed toxicity thresholds.
  • Inorganic constituents represent a risk to aquatic biota even before ore extraction has begun. Specifically, arsenic and selenium exceeded toxicity thresholds in tadpoles from the mine containment pond.
  • The containment pond may be considered an attractive nuisance if it remains a constant open water source.

Microscopic abnormalities observed in pre-mining tissue samples could not be linked to mining activities; future sampling during active mining will help determine if exposure to mining-related constituents leads to histopathological effects.



Specific Tasks

Task 5a: Compile/evaluate existing and newly collected monitoring data from various agencies/sources
Task 5c: Collect/analyze samples from biota with focus on trust resources
Task 7a: Conduct species surveys
Task 17: Determine biological effects of uranium + trace element mixtures


1 Cleveland, D., Hinck, J.E., Lankton, J.S., 2021, Elemental and radionuclide exposures and uptakes by small rodents, invertebrates, and vegetation at active and post-production uranium mines in the Grand Canyon watershed: Chemosphere, vol. 263,

2 Hinck, J.E., Cleveland, D., Brumbaugh, W.G., Linder, G., and Lankton, J., 2017, Pre-mining trace element and radiation exposure to biota from a breccia pipe uranium mine in the Grand Canyon (Arizona, USA) watershed: Environmental Monitoring and Assessment, February 2017

3 Cleveland, D.M., Hinck, J.E. and Lankton, J.S., 2019, Assessment of chronic low-dose elemental and radiological exposure of biota at the Kanab North uranium mine site in the Grand Canyon watershed: Integrated Environmental Assessment and Management 15:112-125,

4 Hinck, J.E., Linder, G., Darrah, A.J., Drost, C.A., Duniway, M.C., Johnson, M.J., Mendez-Harclerode, F.M., Nowak, E.M., Valdez, E.W., Wolff, S., and van Riper III, C., 2014, Exposure pathways and biological receptors--Baseline data for the Canyon Uranium Mine, Coconino County, Arizona: Journal of Fish and Wildlife Management, v. 5, no. 2, p. 422-440

5 Klymus, K.E., Richter, C.A., Thompson, N., and Hinck, J.E., 2017, Metabarcoding of Environmental DNA Samples to Explore the Use of Uranium Mine Containment Ponds as a Water Source for Wildlife: Diversity 2017, v. 9, no. 4.

6 Valdez, E.W., Hanttula, M.K., and Hinck, J.E. 2021. Seasonal activity and diets of bats at uranium mines and adjacent areas near the Grand Canyon. Western North American Naturalist: Vol. 81 :1-18,

7 Mann, R.K., Duniway, M.C., 2020, Vegetation cover and composition data in environments surrounding uranium mines in the Grand Canyon ecosystem, U.S. Geological Survey data release,

8 Minter, K.M., Jannik, G.T., Hinck, J.E., Cleveland, D., Kubilius, W.P.,and Kuhne, W.W., 2019, Biota dose assessment of small rodents sampled near breccia pipe uranium mines in the Grand Canyon watershed: Health Physics 117:20-27

Pinyon Plain (formerly Canyon) Mine Sources:

4 Hinck, J.E., Cleveland, D., Brumbaugh, W.G., Linder, G., and Lankton, J., 2017, Pre-mining trace element and radiation exposure to biota from a breccia pipe uranium mine in the Grand Canyon (Arizona, USA) watershed: Environmental Monitoring and Assessment, February 2017