exposure. Gamma radiation is different from chemical contaminants because it can travel beyond the source, and direct contact is not necessary for exposure to occur. These pathways may be direct, as when someone breathes air that contains radon gas or dust, or may be indirect, as when a worm absorbs a chemical from the soil and the worm is eaten by another animal, which may eventually be eaten by other animals, including people. Exposures occur by eating, drinking, breathing, skin contact, or from gamma-ray emissions from radionuclides. Gamma rays can travel much farther than alpha or beta particles, and can penetrate the body, potentially exposing all of the organs. Radiation can easily penetrate solid materials such as soils or drums.
The exposure pathways are the same for people and for ecological resources, but different pathways are dominant. The exposures of greatest importance from the human health perspective are occupational exposures that occur within mines and enclosed processing facilities, primarily involving inhalation (see Chapter 5). Human health exposures may also occur in the surrounding communities if contamination travels offsite via air, surface water, or groundwater. Exposures of greatest importance for ecological effects occur outside the enclosed facilities, where radon and gaseous chemicals would quickly dissipate. The most significant exposure pathways for ecological resources are anticipated to occur via surface water because of its accessibility and the numerous potential transport mechanisms for dissolved and particle-associated contaminants (e.g., discharge of treated process water into streams; discharge of contaminated groundwater to streams). Such waters may contain chemicals, metals, and radionuclides higher than background or preconstruction conditions, particularly if treatment or waste containment systems fail to perform as designed. However, ecological exposures also may occur through air (e.g., dust, radon), contaminated soil, sediments, or from gamma radiation given off by radionuclides in contaminated materials.
For purposes of description here, it is convenient to address surface water and groundwater as if they are separate entities, although the committee recognizes that surface water and groundwater are part of a single resource. Water moves between surface water and groundwater, and changes in the quantity and quality of one will affect the same parameters in the other.
Disturbances of the land surface associated with uranium mining in Virginia would be expected to have significant effects on both on-site and downstream surface water conditions. These disturbances affect both surface water quantity and quality. Many of these effects are similar to those encountered in other types of mining, although there are some unique risks posed by uranium mining and processing due to the presence of radioactive substances, and co-occurring chemicals such as heavy metals.