Potential Human Health Effects of Uranium Mining from NAS
Key Points
• Uranium mining and processing are associated with a wide range of potential adverse human health risks. Some of these risks arise out of aspects of uranium mining and processing specific to that enterprise, whereas other risks apply to the mining sector generally and still others are linked more broadly to large-scale industrial or construction activities. These health risks typically are most relevant to individuals occupationally exposed in this industry but certain exposures and their associated risks can extend via environmental pathways to the general population.
• Protracted exposure to radon decay products generally represents the greatest radiation-related health risk from uranium-related mining and processing operations. Radon’s alpha-emitting radioactive decay products are strongly and causally linked to lung cancer in humans. Indeed, the populations in which this has been most clearly established are uranium miners that were occupationally exposed to radon.
• In 1987, the National Institute for Occupational Safety and Health (NIOSH) recognized that current occupational standards for radon exposure in the United States do not provide adequate protection for workers at risk of lung cancer from protracted radon
decay exposure, recommending that the occupational exposure limit for radon decay products should be reduced substantially. To date, this recommendation by NIOSH has not been incorporated into an enforceable standard by the Department of Labor’s Mine Safety and Health Administration or the Occupational Safety and Health Administration.
• Radon and its alpha-emitting radioactive decay products are generally the most important, but are not the only radionuclides of health concern associated with uranium mining and processing. Workers are also at risk from exposure to other radionuclides, including uranium itself, which undergo radioactive decay by alpha, beta, or gamma emission. In particular, radium-226 and its decay products (e.g., bismuth-214 and lead-214) present alpha and gamma radiation hazards to uranium miners and processors.
• Radiation exposures to the general population resulting from off-site releases of radionuclides (e.g., airborne radon decay products, airborne thorium-230 (230Th) or radium-226 (226Ra) particles, 226Ra in water supplies) present some risk. The potential for adverse health effects increases if there are uncontrolled releases as a result of extreme events (e.g., floods, fires, earthquakes) or human error. The potential for adverse health effects related to releases of radionuclides is directly related to the population density near the mine or processing facility.
• Internal exposure to radioactive materials during uranium mining and processing can take place through inhalation, ingestion, or through a cut in the skin. External radiation exposure (e.g., exposure to beta, gamma, and to a lesser extent, alpha radiation) can also present a health risk.
• Because 230Th and 226Ra are present in mine tailings, these radionuclides and their decay products can—if not controlled adequately—contaminate the local environment under certain conditions, in particular by seeping into water sources and thereby increasing radionuclide concentrations. This, in turn, can lead to a risk of cancer from drinking water (e.g., cancer of the bone) that is higher than the risk of cancer that would have existed had there been no radionuclide release from tailings.
• A large proportion of the epidemiological studies performed in the United States, exploring adverse health effects from potential off-site radionuclide releases from uranium mining and processing facilities, have lacked the ability to evaluate causal relationships
(e.g., to test study hypotheses) because of their ecological study design.
• The decay products of uranium (e.g., 230Th, 226Ra) provide a constant source of radiation in uranium tailings for thousands of years, substantially outlasting the current U.S. regulations for oversight of processing facility tailings.
• Radionuclides are not the only uranium mining- and processing-associated occupational exposures with potential adverse human health effects; two other notable inhalation risks are posed by silica dust and diesel exhaust. Neither of these is specific to uranium mining, but both have been prevalent historically in the uranium mining and processing industry. Of particular importance is the body of evidence from occupational studies showing that both silica and diesel exhaust exposure increase the risk of lung cancer, the main risk also associated with radon decay product exposure. To the extent that cigarette smoking poses further risk in absolute terms, there is potential for increased disease, including combined effects that are more than just additive.
• Although uranium mining-specific injury data for the United States were not available for review, work-related physical trauma risk (including electrical injury) is particularly high in the mining sector overall and this could be anticipated to also apply to uranium mining. In addition, hearing loss has been a major problem in the mining sector generally, and based on limited data from overseas studies, may also be a problem for uranium mining.
• A number of other exposures associated with uranium
mining or processing, including waste management, also could carry the potential for adverse human health effects, although in many cases the detailed studies that might better elucidate such risks are not available.
• Assessing the potential risks of multiple combined exposures from uranium mining and processing activities is not possible in practical terms, even though the example of multiple potential lung carcinogen exposures in uranium mining and processing underscores that this is more than a theoretical concern.
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