Uranium Mining in Virginia Scientific, Technical, Environmental, Human Health and Safety, and Regulatory Aspects of Uranium Mining and Processing in Virginia (2012) / Chapter Skim
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5 Potential Human Health Effects of Uranium Mining, Processing, and Reclamation
5 Potential Human Health Effects of Uranium Mining, Processing, and Reclamation
Pages 123-177
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From page 123... ...
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.
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From page 124... ...
• 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)
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From page 125... ...
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.
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From page 126... ...
organized stakeholder meetings that included uranium miners and processors in Wyoming, Texas, Colorado, and Utah. The stakeholders expressed numerous health-related concerns, including concerns about exposure to alpha radiation via inhalation or ingestion of dust particles containing radon decay products, exposure to both radiation and particulate uranium via inhalation, ingestion and inhalation of ore dust, and exposure to diesel particulate matter (Miller et al., 2008)
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From page 127... ...
In most exposure scenarios related to uranium mining and processing, beta radiation presents a greater external than internal radiation hazard. For example, the beta dose rate from uranium decay products is negligible immediately after separation of ura nium, but can produce a beta dose rate on contact of about 150 mrem/hr several months after separation because of the buildup of 234Th (USNRC, 2002)
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From page 128... ...
decay series. The potential for occupational exposure to uranium or thorium and their decay products can vary greatly depending on numerous factors, including the type of ore deposit, uranium grade, mineralogy of deposit, production capacity, uranium mining method, production rate, variation in process methods (e.g., types of crushers or grinders)
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From page 129... ...
. exhaustive compilation of all recommendations regarding radon and uranium occupational exposure limits, but rather is intended to highlight the complexity and the differences among the guidelines as context for ensuing descriptions of dose and exposure standards and regulations both in this chapter and in Chapter 7.
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From page 130... ...
. For example, uranium miners working in underground mines generally have a much greater potential for exposure to radon and radon decay products during the min
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From page 131... ...
Generally, the high est potential radiation-related health risk for uranium mining or processing facil ity workers is lung cancer associated with inhaling uranium decay products (more specifically, radon decay products) , as well as other non-lung-cancer risks associated with gamma radiation exposure on-site.
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From page 132... ...
RS-G-1.6 mining and processing of raw materials MSHA 30 CFR Part 57 Underground mines 4 WLM/yr Max = 1 WL USNRC 10 CFR Part 20 Uranium processing facilities DAC @100% equilibrium: and in situ leaching facilities 30 pCi/L ALI = 4 WLM OSHA 29 CFR § 1910.1090 Processing facilities not DAC@100% equilibrium: regulated by the U.S. Atomic 30 pCi/L Energy Acta ALI = 4 WLMb DOE 10 CFR Part 835 DOE facilities DAC @100% equilibrium: 80 pCi/L ALI= 10 WLM Action Level (Bq/m3)
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From page 133... ...
from internal exceed 50 mSV in and external 1 year None stated 5 rem/yr Not addressed Respiratory protection required at levels ≥10 WL Limits specified in Limits are Total Effective Dose Table 1 of Appendix governed by the Equivalent of 5 rem B of 10 CFR Part 20 total exposure from internal plus external References USNRC 1.25 rem per Posting required at 25% of limits specified quarter the exposure limit above Limits specified in Limits are Total Effective Dose Posting required at 10% of Appendix A of 10 governed by the Equivalent of 5 rem the DAC CFR Part 835 total exposure from internal and external Not addressed Not addressed Effective dose of Not addressed 20 mSv/year averaged over 5 years, not to exceed 50 mSV in one year NOTES: WLM = working level month, DAC = derived air concentration, ALI = annual limit on intake, REL = recommended exposure limit. SOURCE: Courtesy Jim Neton, NIOSH, with modifications.
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From page 134... ...
1 rem = 0.01 Sv Cumulative radon decay product exposure is often measured in working levels (WL) and working level months (WLM)
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From page 135... ...
. Therefore, thoron, a radioactive decay product of 232Th, as noted above, is anticipated to present a much lower risk to workers than exposure to radon-222 decay products.
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From page 136... ...
. Once deposited in the lung, the short-lived radon decay products, 218Po and 214Po, rather than the radon gas, deliver the majority of the radiation dose in the form of alpha particles to the respiratory epithelium.
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From page 137... ...
Even with these limitations, the overwhelming majority of the epidemiological studies have demonstrated a positive linear dose-response relationship between radon decay product exposure and lung cancer; that is, the greater the exposure, the greater the risk, falling on a straight line (Samet, 1988; NRC, 1999b; ATSDR, 2008)
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From page 138... ...
. Throughout this early period, lung cancer in miners was of little public health concern in the United States, despite an emerging medical interest in occupational
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From page 139... ...
POTENTIAL HUMAN HEALTH EFFECTS FIGURE 5.3 Historical time line for the understanding of lung cancer occurrences in uranium miners. SOURCE: Courtesy of P.D.
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From page 140... ...
. The BEIR VI estimates of the risks posed by lower level radon decay product exposures are particularly relevant to the general public living near ura nium mining and processing operations, because radon decay product exposure has been shown to be an important source of radiation exposure to nearby offsite communities (SC&A, 2011)
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From page 141... ...
For example, the BEIR VI committee observed that exposure to both radon and tobacco usage increases lung cancer risk higher than simply an addi tive effect, but less than a full multiplicative degree of risk. Thus, the risk of lung cancer among uranium miners who smoke cigarettes is greater, in absolute and relative terms, than the risk for cigarette smokers who do not experience radia tion exposure; moreover, the incremental increase in absolute risk (reflected in 1 Radon decay product concentrations are expressed in working levels (WL)
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From page 142... ...
. Although the occupational lung carcinogenicity of radon decay product exposure has been clearly established for decades, the causal association between occupational radon exposure and cancer of other types (i.e., nonlung cancer)
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From page 143... ...
noted a linear positive relationship between radon decay product exposure and nonmalignant respiratory disease in nonsmoking uranium miners, that the authors attributed to diffuse parenchymal radiation damage. Occupational Exposure Guidelines for Radon In many cases, the primary radiation risks associated with uranium mines and processing facilities are exposure to radon decay product exposure (Ahmed, 1981; NIOSH, 1987)
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From page 144... ...
Radon Risk Estimates The NRC's BEIR VI Committee estimated -- based on projections (i.e., interpolations from the radon-exposed underground miner studies they examined) -- that 18,600 lung cancer deaths occur each year in the United States from nonoccupational exposures to radon decay products (NRC, 1999b)
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From page 145... ...
7% 5% FIGURE 5.4 Percent contribution of various sources of radiation exposure to the total effective dose per individual in the United States for 2006. Percent values have been rounded to the nearest 1 percent, except for those < 1 percent.
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From page 146... ...
. Consistent with the prevalence of exposure and its adverse effects, residential radon decay product exposure is believed to be the second leading cause of lung cancer overall, the primary cause of lung cancer among individuals who have never smoked, and the leading environmental cause of cancer mortality in
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From page 147... ...
. However, 40 CFR Part 61, Subpart B limits the effective dose from radon decay products to 10 mrem/yr for members of the public.
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From page 148... ...
(i.e., member of the public within 80 km expected to receive the greatest exposure to radon decay products) was estimated to receive a dose of 28 mrem/year, with a 1.6 in 100,000 chance of developing a latent cancer fatality; while the maximum estimated population dose living within 80 km of the site was 200 person-rem/yr, with a 1.4 in 1,000 chance of developing a latent cancer fatality.
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From page 149... ...
. The decay products of uranium (e.g., 230Th, 226Ra)
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From page 150... ...
recently published a detailed review of adverse uranium health effects (ATSDR, 2011) , concluding -- as have other reviews -- that the primary effect from uranium exposure is renal toxicity.
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From page 151... ...
Additional epidemiological data relevant to this question among uranium miners and processors will be provided in a later section on silica exposure. Assessing the causal relationships between uranium exposures in miners and adverse health outcomes presents a challenge because of confounding by occupational exposures to radon decay products, silica, and diesel exhaust.
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From page 152... ...
Several retrospective cohort mortality studies of uranium processing workers where exposure to radon decay products is expected to be less than that of underground miners, although not negligible, have been performed. These limited studies have failed to establish a consistent pattern of excess mortality among uranium processing workers (Archer et al., 1973a; Pinkerton et al., 2004; Boice et al., 2008)
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From page 153... ...
Nonethe less, the NRC (2008b) report concluded that an increased risk of lung cancer due to the inhalation of uranium particulates cannot be ruled out, especially because alpha particles are known to be emitted by such dusts.
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From page 154... ...
. During uranium processing, a large percentage of the uranium is removed, leaving the majority of the decay products in the tailings.
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From page 155... ...
Along with exposure to radon decay products, inadequate containment of uranium tailings most likely represents the highest potential source of radiation exposure, related to uranium mining activities, to the general public. Landa and Gray (1995)
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From page 156... ...
The researchers did not find any evidence that the operation of the uranium mines and processing facilities increased the cancer or mortality rates for the nearby population. Boice et al.
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From page 157... ...
3 is a basic metric of epidemiological risk derived from mortality studies such as those done among uranium mining and processing cohorts. A recent report of further follow-up of the Colorado Plateau cohort (a large group study of former uranium miners from the U.S.
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From page 158... ...
An updated analysis of 1,484 employees of seven uranium processing facilities in the Colorado Plateau -- with nearly 60 years of follow-up from 1940 through 1998 -- presents a relatively robust database because of the size of the cohort combined with the duration of follow-up (this cross product is summarized as person-years; in this analysis, 50,000 person-years of follow-up)
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From page 159... ...
uranium processing workers was increased by nearly 40 percent. Silicosis, in its classic form, is a chronic process that becomes clinically manifest more than a decade after initiation of first exposure.
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From page 160... ...
It is noteworthy, however, that although the analysis of silica-associated lung cancer risk in mining operations was an important part of the IARC review, these data generally excluded uranium-exposed workers, because this occupation involves exposure to radon decay products, a potentially confounding lung carcinogenic exposure discussed above. The sole exception was the inclusion in the IARC review of a lung cancer case-control study of radiographic silicosis in uranium miners from the Colorado Plateau (see Samet et al., 1994; IARC, 1997, Table 19, p.
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From page 161... ...
. An analysis of lung cancer mortality in the German mining cohort observed an independent association with silica exposure, but also did not assess potential interactions (Taeger et al., 2008)
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From page 162... ...
. Because of the latency between initial exposure and silica-related diseases such as silicosis, lung cancer, and COPD, the epidemiological data summa rized above represent exposure conditions that span decades.
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From page 163... ...
for lung cancer associated with occupational exposure to diesel exhaust of 1.33 (95 percent CI of 1.24-1.44)
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From page 164... ...
. In addition to the potential risk of lung cancer, cardiovascular and acute and chronic pulmonary effects of diesel emissions have been documented (California EPA, 1998; USEPA, 2002)
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From page 165... ...
Labor Department, the average number of lost workdays from injury for all other occupations was 8 days. Electrical Hazards As mine operators decrease their use of diesel-powered equipment in underground mines -- to decrease exposure to diesel fumes -- the need for additional high-voltage electricity to power equipment increases, increasing the potential for electrical accidents.
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From page 166... ...
. In a study of 31,325 uranium miners in Germany from 1946 to 1990, hearing impairment was found in 4,878 miners (16 percent)
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From page 167... ...
Noise -- Public/Off-site Exposure Health effects of noise in a community setting are based upon speech interference and sleep interference, rather than noise-induced hearing loss. When ambient sound levels reach a level of 50 decibels (measured on the A-scale to simulate the human hearing range)
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From page 168... ...
Vibration -- Occupational and Off-site Sound is the transmission of vibration in the audible range -- from 20 Hz to 20,000 Hz -- but energy present in the range below 20 Hz can still cause adverse health effects. Whereas sound is airborne, vibration is primarily structureborne.
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From page 169... ...
In uranium processing, uranium extraction is a chemically dependent process, with certain commonly used substances (e.g., sulfuric acid) that are known to be hazardous, whereas other process chemicals have uncertain hazard status.
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From page 170... ...
. Welding, Metalworking Fluids, and Other Maintenance-Related Exposures Mining and processing operations require extensive onsite maintenance operations that include welding, machining, and various other equipment and parts maintenance and repair work.
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From page 171... ...
In areas of the world where arsenic has been present as a uranium contaminant, exposure has been a major issue of occupational health risk among mining and process workers. Although arsenic is a potent toxin with a myriad of adverse effects, its carcinogenic poten tial has been particularly salient among uranium miners, in particular because of their concomitant exposure to radon (Taeger et al., 2008; Tomášek et al., 1994)
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From page 172... ...
Epidemiological studies of sulfuric acid manufacturing worker cohorts have been limited to production processes in which the source of sulfur is sulfur contained in mineral ore. Acrylamide and Related Polymeric Flocculants These materials are used in uranium refining, together with mechanical separation techniques (e.g., countercurrent decantation and further clarification steps)
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From page 173... ...
. Although ques tions of potential human toxicity are raised by these studies, the same imitated exposure scenarios in an enclosed system, as noted for the tertiary amines, are also relevant to decanol's application in uranium processing.
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From page 174... ...
Hydrogen peroxide can be used in both early and later uranium processing steps. In the initial leaching step, it facilitates solubilizing uranium by acting as an oxidizing agent (sodium chlorate and ferrous sulfate also can be employed as oxidants; adverse health effects would be limited to unlikely ingestion sce narios)
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From page 175... ...
The epidemiological data from studies of radonexposed miners clearly demonstrate that protracted radon decay product exposure causes lung cancer in a dose-dependent manner, and that it can act independently of other known carcinogenic exposures as well as having a greater than additive effect (i.e., synergistic effect) with co-exposures to other lung carcinogens (e.g., cigarette smoking)
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From page 176... ...
Workers are also at risk from exposure to other radionuclides, including uranium itself, which undergo radio active decay by alpha, beta, or gamma emission. In particular, radium-226 and its decay products (e.g., bismuth-214 and lead-214)
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From page 177... ...
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. Thus, workers in the uranium mining and processing industry can be co-exposed to several separate lung carcinogens, including radon decay products, silica, and diesel.
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