Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
The extent of damage from exposure to a uranium compound depends on the solubility of the
compound and the route of exposure. In most health assessments evaluating the health effects of
uranium exposure, inhalation, ingestion, and external radiation are all considered. Although
absorption of some soluble compounds through the skin is possible, such dermal exposures
generally are not significant. For inhalation or ingestion of soluble or moderately soluble
compounds such as uranyl fluoride (UO2F2) or uranium tetrafluoride (UF4), the uranium enters
the bloodstream and reaches the kidney and other internal organs, so that chemical toxicity is of
primary importance. For inhalation of insoluble compounds such as uranium dioxide (UO2) and
triuranium octaoxide (U3O8, the uranium compound typically found in uranium ore), the uranium
is generally deposited in the lungs and can remain there for long periods of time (months or
years). The main concern from exposure to these insoluble compounds is increased cancer risk
from the internal exposure to radioactivity. Ingested insoluble compounds are poorly absorbed
from the gastrointestinal tract and are only retained in the body for a short time, thus generally
having a low toxicity.
Today’s mining procedures include mine dust control to reduce the potential for inhalation; dose
measurements to ensure that safe levels of exposure are not exceeded; precautionary management
practices followed by miners; and in the case of underground mines like the proposed Roca
Honda Mine, proper ventilation.
Radon
Radon gas is another exposure risk and one which is more related to mining than to processing or
disposal, especially underground mining. Thus, it is more relevant to the proposed Roca Honda
Mine than to open pit mines. Radon gas exposure is somewhat different than other forms of
radionuclide exposure in that it is found naturally throughout the U.S. It has the potential for
exposure to the public at large, even if not near a mine.
Radon is a naturally occurring radioactive gas found at elevated concentrations in many areas of
the U.S., including basements of homes and other underground structures. Based on radon
exposure studies, the EPA has suggested that homeowners should provide extra ventilation in
basements or take other measures if radon levels exceed 4 piC/L (picocuries per liter). One
common solution is an installed vacuum system that collects air under the foundation of the home
and exhausts it before radon can penetrate walls and create exposure.
The EPA has found that radon gas is the number two cause of lung cancer in the United States,
behind smoking, and is responsible for 21,000 lung cancer deaths per year—most of which
(18,000) are from smokers, demonstrating the link between radon exposure health risk and
smoking. When radon decays, it releases small radioactive particles that drift in the air. Because
these radioactive particles adsorb (attach) to the surface of small particulate matter in the air, they
can be inhaled if dust or small particles are inhaled. One source of small particulate matter is
cigarette smoke. Thus, radon particles can absorb to the smoke that is inhaled by smokers, move
deep into the lung, and stay there while exposing the lung to radiation. There has been a
correlation between smoking in uranium mines and lung cancer, and the combination of smoking
and radon exposure increases cancer risk considerably. Smoking allows fine particulates to which
radioactive particles have adsorbed to travel deep into the lungs and attach to the surface of the
lung. Absent the fine particles, the radon particles are not as likely to find a mechanism to attach
to the lungs.
DEIS for Roca Honda Mine, Cibola National Forest 435