Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
predominant isotope (comprising about 99.3 percent of naturally occurring uranium) is termed
“U-238” (sometimes written U238 or 238 U) and forms a series of decay products including
radionuclides radium-226 and radon-222. The decay process continues until a stable,
nonradioactive decay product is formed – lead (Pb-206, in the case of U-238) (USEPA, 2011g).
These decay products emit energetic particles or energetic waves that travel through a medium or
space and which can damage the tissue in a living organism. The amount and duration of
radiation exposure determines the severity or type of health effects. These heavy elements also
have a chemical toxicity, which is the degree to which a substance is poisonous to a living
organism.
Because the amount of exposure and uptake of uranium could determine the severity of the
impact on wildlife, it is important to understand how wildlife can be repeatedly exposed to
uranium and its decay products in the environment. Unless properly controlled, uranium and
other radionuclides could be transported through the environment via atmospheric deposition
(sedimentation of uranium or radionuclide particles from the air), dust, runoff, erosion and
deposition, groundwater and surface water, and the food chain. Groundwater and surface water
could become contaminated with uranium and its decay products from mining activities. Soil and
food (prey species) could also have elevated levels of uranium and decay products due to mining
activities (Hincks et al., 2010). When living organisms are exposed repeatedly to these
radionuclides, toxins can build up in their tissues over time. Bioaccumulation is the buildup of a
toxin in a living organism over time. Predator species, like the mountain lion, tend to accumulate
higher concentrations of substances released into the environment because they are exposed to
more pathways than prey species. For this analysis, major exposure pathways include ingestion,
inhalation, absorption, and bioaccumulation. Figures 54 and 55 document these potential uranium
and radionuclide exposure pathways.
The extent and nature of the health effects on wildlife associated with exposure to uranium and its
decay products remain somewhat inconclusive. Very little research has been conducted on the
biological impacts of uranium and other radionuclide exposure on wildlife. Even fewer studies
have attempted to quantify the risks to wildlife caused by the chemical or radiation releases at
uranium mining sites. Though research is limited, it does suggest that uranium and other
radionuclides can affect the survival, growth, and reproduction of plants and animals (Hincks et
al., 2010). Exposure to chemical and radiation hazards is influenced by an animal’s life history
and surrounding environment (Hincks et al., 2010). The sensitivity of wildlife to radiation and
chemical exposures is also influenced by body size. Large-bodied species are typically more
vulnerable to high levels of ration exposure as described above than small-bodied species (BLM,
2011). Animal studies have shown that sufficiently high doses of uranium ingested into the body
may damage the kidneys, and at a still greater dose may cause death (Kathern, 2011).
Historical mining and milling practices in this region in high localized levels of uranium and
other radionuclide exposure to living organisms. Even a small increase in uranium contamination
could hypothetically contribute to adverse impacts on wildlife. While past uranium mining in the
area has contributed to contamination, there have been limited studies on the impacts of uranium
on wildlife (EPA, 2011g). Although radiation from uranium and its decay products does not travel
far, in the absence of proper ore handling and controls, uranium particles could be transported off
the permit area due to the action of wind and water. If groundwater or surface water were to
become contaminated, uranium and radionuclides could impact areas outside of the permit area.
234 DEIS for Roca Honda Mine, Cibola National Forest