Drinking-water contribution to natural background radiation

The average concentrations of naturally occurring radionuclides in drinking water are estimated from recent measurements and are used to estimate the annual effective dose equivalent associated with drinking water due to the different radionuclides. The annual effective dose equivalents are determined from the annual intake of these radionuclides using dosimetric information based on ICRP Publication 30 dosimetric models and cohort analysis considering risk coefficients developed by the U.S. Environmental Protection Agency using data from the report of the Biological Effects of Ionizing Radiation Committee (BEIR III) of the National Academy of Sciences. The resulting contribution from drinking water sources to the annual effective dose equivalent is in the range of 0.002 to 0.05 mSv/y (0.2-5 mrem/yr) for those using community drinking water supplies (approximately 216 million people in the United States). The contribution to the annual effective dose equivalent from 222Rn dissolved in water is in the range of 0.8-30 mu Sv/y (0.08-3 mrem/yr) based on the inhalation pathway following the release of 222Rn from drinking water.     

One perspective on stakeholder involvement at Hanford

The Hanford nuclear site in Washington State had a major role in the production of nuclear weapons materials during the Manhattan Project in World War II and during the Cold War that followed. The production of weapons-grade radionuclides produced a large amount of radioactive byproducts that have been stored since the mid-1900s at the Hanford Site. These by-product radionuclides have leaked from containment facilities into the groundwater, contaminated buildings used for radionuclide processing, and also contaminated the nuclear reactors used to produce weapons-grade uranium and plutonium. This issue has been a major concern to Hanford stakeholders for several decades, and the U.S. Department of Energy, the U.S. Environmental Protection Agency, and the Washington State Department of Ecology established a Tri-Party Agreement in 1989, at which time Hanford ceased production of nuclear weapons materials and began a major effort to clean up and remediate the Hanford Site's contaminated groundwater, soil, and facilities. This paper describes the concerns of stakeholders in the production of nuclear weapons, the secrecy of Hanford operations, and the potential impacts to public health and the environment from the unintended releases of weapons-grade materials and by-products associated with their production at the Hanford Site. It also describes the involvement of public stakeholders in the development and oversight by the Hanford Advisory Board of the steps that have been taken in cleanup activities at the Hanford Site that began as a major effort about two decades ago. The importance of involvement of the general public and public interest organizations in developing and implementing the Hanford cleanup strategy are described in detail.     

The assessment of human exposure to radionuclides from a uranium mill tailings release and mine dewatering effluent

This study provides an assessment of human exposure to radiation from a river system contaminated by radionuclides of the 238U decay series released through a dam break at a uranium mill tailings pond and by the continuous discharge of dewatering effluent from 2 uranium mines. The in vivo analyses of radionuclides in 6 Navajo Indians who lived near the river indicate no detectable elevations above background concentrations. Dose estimates for inhalation of suspended river sediment indicate a maximum annual 50-yr dose commitment of 204 mrem to the endosteum. Estimates of doses (50-yr dose commitments) from the ingestion of livestock range between 1 mrem (to liver) and 79 mrem (to bone) suggest that the major contribution to human exposure is from mine dewatering effluent that has been continuously released into the river system for many years. Although the estimated exposures do not exceed existing state or federal regulations, their magnitude justifies further measurement of radionuclides in animals and in the natural environment and the consideration of strategies to reduce radiation exposure to humans and animals.     

Study of radon daughter concentrations in Polk and Hillsborough counties

The present study finds the average excess dose equivalent resulting from external gamma radiation on reclaimed land to be 17 mrem/yr (whole body); the highest excess is 166 mrem/yr, well below the NCRP limit that might be compared (500 mrem/yr). In contrast, the annual average excess exposure from radon-daughter inhalation on reclaimed land has been found to be 540 mrem/yr to the whole lung, more than twice that resulting from natural background in the study area and more than 5 times the national average dose equivalent reported in NCRP 45 (100 mrem/yr). Moreover, a significant number of individuals presently receive lung doses exceeding limits inferred from NCRP recommendations. These results indicate the need for corrective action to reduce radiation exposure of members of the general population whose exposure exceeds dose limiting recommendations and possibly to reduce radiation exposures well below these limits, thereby lowering risks even further.     

A field study of Ra accumulation in trout with assessment of radiation dose to man

The purpose of this study was to determine the concentrations of 226Ra in edible fish from surface ponds near an open pit U mine. Because one reclamation plan for the U mine proposed formation of an artificial lake in the open pit, potential radiation dose to man from ingestion of fish needed to be investigated. Trout were collected from four existing ponds which varied in mean 226Ra concentration from 12-33 pCi/l. and in Ca concentration from 30-330 mg Ca/l. Radium and Ca accumulation in trout flesh, skin, fins and bone were measured. Geometric mean concentrations of 226Ra in trout flesh from four ponds ranged from 6.3-30 pCi/kg wet weight. The distribution of Ra in the trout body was similar to that of Ca. Of the total 226Ra in trout carcasses, 6% was in flesh, 25% was in skin, 28% was in fins, and 41% was in bone. Mean concentration factors for 226Ra in trout flesh from the four ponds ranged from 0.29-2.5. Bone concentration factors were up to 260 times higher than for flesh. Observed ratios (Ra/Ca in fish tissue divided by Ra/Ca in water) were used to normalize the differences in Ca availability among the locations. Observed ratios were higher in all tissues of fish which had been in the ponds for a longer time, indicating that 226Ra concentrations in fish may increase with continued exposure to the nuclide. The calculated dose equivalent commitment to human endosteal tissue ranged from 0.2-2 mrem per fish consumed, depending on the assumed dietary and environmental parameters. Neglecting the consumption of trout skin underestimated the ingestion dose from 226Ra by a factor of 5-10. Estimated annual dose equivalent rates to human endosteal tissue ranged from 1.0-83 mrem/yr for an individual who consumed one fish per week for a 50-yr period. The dose to man from ingestion of 226Ra in fish would not likely preclude the establishment of a recreational lake at this site.     

Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data

This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with measurement uncertainty. The following papers detail how these shortcomings are overcome to achieve the goals of the three-part series.     

Population doses, excess deaths and loss of life expectancy from mass chest x-ray examinations in Japan--1980

The number of mass chest x-ray examinations in Japan in 1980 was 26.6 million and the average effective dose equivalent was 26 mrem per examination. The genetically significant dose was .017 mrem per person per year, the per caput mean marrow dose was 5.9 mrem, the leukemia significant dose was 5.2 mrem and the malignancy significant dose was 2.8 mrem. The excess deaths were calculated to be 70-280 depending on the risk model used. Those would be in excess to the 3.7 million cancer deaths normally expected among the examined population. The loss of life expectancy calculated with a relative risk model was 38 yr for males and 43 yr for females due to leukemia with a latent period of 2 yr and an expression period of 25 yr, and 12 yr for males and 14 yr for females due to other cancers with a latent period of 10 yr and an expression period of lifetime in the 20-24 age group.     

Valuation of environmental quality and eco-cultural attributes in Northwestern Idaho: Native Americans are more concerned than Caucasians

Valuation of features of habitats and ecosystems usually encompasses the goods and services that ecosystems provide, but rarely also examine how people value ecological resources in terms of eco-cultural and sacred activities. The social, sacred, and cultural aspects of ecosystems are particularly important to Native Americans, but western science has rarely examined the importance of eco-cultural attributes quantitatively. In this paper I explore differences in ecosystem evaluations, and compare the perceptions and evaluations of places people go for consumptive and non-consumptive resource use with evaluations of the same qualities for religious and sacred places. Qualities of ecosystems included goods (abundant fish and crabs, butterflies and flowers, clean water), services (complexity of nature, lack of radionuclides that present a health risk), and eco-cultural attributes (appears unspoiled, scenic horizons, noise-free). Native Americans and Caucasians were interviewed at a Pow Wow at Post Falls, Idaho, which is in the region with the Department of Energy’s Hanford Site, known for its storage of radioactive wastes and contamination. A higher percentage of Native American subjects engaged in consumptive and religious activities than did Caucasians. Native Americans engaged in higher rates of many activities than did Caucasians, including commune with nature, pray or meditate, fish or hunt, collect herbs, and conduct vision quests or other ceremonies. For nearly all attributes, there was no difference in the relative ratings given by Native Americans for characteristics of sites used for consumption/non-consumptive activities compared to religious/sacred places. However, Caucasians rated nearly all attributes lower for religious/sacred places than they did for places where they engaged in consumptive or non-consumptive activities. Native Americans were less concerned with distance from home for consumptive/non-consumptive activities, compared to religious activities.     

Chemical and ecotoxicological characterization of Columbia River sediments below the Hanford site (USA)

Columbia River sediments were characterized (metals, organics, porewater toxicity) with samples (n=12) from four dams below the Hanford site. Analyses were supplemented with colocated radionuclide data, along with comparable data from the Priest Rapids dam, immediately upriver from Hanford. Although not statistically significant (Bonferroni P>0.05), metals were generally highest at Priest Rapids, relative to downriver dams. Semivolatiles, Aroclors, and organochlorine pesticides were below method reporting limits. Radionuclide differences across locations were minor (Bonferroni P>0.05). Whereas Microtox showed little toxicity, Daphnia IQ tests exhibited measurable toxicity at all locations (EC50 = 22 - 78% porewater). Ecotoxicological benchmarks for metals were exceeded at several locations, most notably at Priest Rapids. Except for K-40, radionuclides were below benchmarks. Overall, chemistry and ecotoxicity results suggested that sediments may pose a risk to benthic biota, likely due to metals (derived largely from upriver mining) or factors associated with a reducing environment (e.g., low oxygen, high ammonia).     

An assessment of drinking-water supplies on the Hanford site: an evaluation conducted at a federal nuclear facility in southeastern Washington state

Drinking water is supplied to most U.S. Department of Energy (DOE) facilities on the Hanford Site by DOE-owned, contractor-operated pumping and distribution systems. Water is primarily obtained from the Columbia River, but some facilities use water from on-site groundwater wells. Because of the large amount of radioactive and chemical waste produced, stored, and disposed of at Hanford, some people are concerned that waste materials are contaminating on-site drinking-water supplies. This paper describes the drinking-water facilities and treatment requirements on the Hanford Site and summarizes radiological and non-radiological water quality data obtained from water samples collected from each drinking-water system in use during 2001 and 2002. Monitoring data show that Hanford-produced radionuclides are measurable in some drinking-water samples. The only non-radiological contaminants detected either were by-products of the chlorination process or came from off-site agricultural activities. Contaminant level values were, in all cases, below state and federal drinking-water limits. This information will provide assurance to current employees and future site developers that drinking water on the Hanford Site is safe for public consumption.     

Assessment of radionuclide contents in food in Hong Kong

Baseline values of concentrations of the natural radionuclides (238U, 226Ra, 228Ra/232Th, 210Pb) and artificial radionuclides (137Cs, 60Co) in food and drinks (tap water, milk, and water-based drinks) were determined by gamma spectroscopy. All food and drinks were found to contain detectable 40K contents: 0.1 to 160 Bq kg(-1) (fresh mass) for food and 0.006 to 61 Bq L(-1) for drinks. Most of the other natural radionuclides in solid food were found to have contents below the minimum detectable activities (MDA). More samples in the leafy vegetable, tomato, carrot and potato categories contained detectable amounts of 228Ra than the meat, cereal, and fish categories, with concentrations up to 1.2 Bq kg(-1) for the former categories and 0.35 Bq kg(-1) for the latter categories. The 238U and 226Ra radionuclides were detectable in most of the water-based drink samples (reaching 0.22 and 0.015 Bq kg(-1), respectively), and the 228Ra and 210Pb radionuclides were detectable in fewer water-based drink samples. The 137Cs contents in solid food were detectable in most of the solid food samples (reaching 0.59 Bq kg(-1)), but in drinks the 137Cs contents were very low (the maximum value is 0.23 Bq L(-1)) and normally lower than the MDA values. Nearly all the 60Co contents in food and drinks were below the MDA values and their contents were below those of 137Cs. The results indicate that drinks provide higher intake of natural radionuclides than solid food, but the solid food provides higher intake of 137Cs than drinks. From the measured concentrations, estimates were made on the consumption rate of radionuclides from food and drinks. The health effects due to the ingestion of the radionuclides were evaluated by calculating the committed effective dose. The committed effective dose due to the ingestion of natural radionuclides was estimated to be 69 microSv and 280 microSv for an adult male and female, respectively. The committed effective dose due to the ingestion of 137Cs and 60Co was estimated to be 0.5 microSv for both an adult male and female. The contributions from these two artificial radionuclides were less than those from the natural radionuclides by a factor of more than 100 and were also below the 1 mSv limit set in the new ICRP recommendations.     

Comparison of doses and risks obtained from dose reconstructions for historical operations of federal facilities that supported the development,production, or testing of nuclear weapons

Five dose reconstruction projects focusing on historical public exposures from U.S. government nuclear facilities have been completed in the last 12 y (Fernald, Hanford, Nevada Test Site, Oak Ridge, Rocky Flats). Using information available in published reports, doses and excess health risks of the most serious contaminants in each study are compared for representative maximally and typically exposed individuals. For both the representative maximally exposed individual and the representative typically exposed individual, the highest excess risks of cancer incidence were from 131I released from Hanford, Nevada Test Site, and Oak Ridge and 222Rn released from Fernald (with central estimates for maximally exposed individuals approaching or exceeding 10(-2)); the lowest risks for both maximally and typically exposed individuals were from 239/240Pu and carbon tetrachloride released from Rocky Flats. Excess health risks to the representative maximally exposed individual were at or below 10(-40 for releases from Rocky Flats. For representative typically exposed individuals, the excess risks from releases of mixed radionuclides in the Clinch River (Oak Ridge), PCBs in East Fork Poplar Creek (Oak Ridge), and both plutonium and carbon tetrachloride released from Rocky Flats were mostly below 10(-5).     

Individual thyroid dose estimates for a case-control study of chernobyl-related thyroid cancer among children of Belarus--part II. Contributions from long-lived radionuclides and external radiation

Significant quantities of long-lived radionuclides were released to the environment during the Chernobyl nuclear power plant accident in 1986. These radionuclides contributed to radiation doses due to ingestion of contaminated foods and external exposure from the ground deposition that resulted. The contributions of these exposure pathways to thyroid doses received by subjects of an epidemiologic study of children from Belarus are evaluated and presented. The analysis shows that ingestion of the long-lived radionuclides, primarily radiocesium, typically contributed a small percentage of the total thyroid dose received by the study subjects. The median and mean fractional contributions were 0.76 and 0.95%, respectively. The contribution of external exposure to the thyroid dose was generally larger and more variable, with median and mean contributions of 1.2 and 1.8% of the total thyroid doses, respectively. For regions close to the reactor site, where radionuclide deposition was highest, the contributions of radiocesium ingestion and external exposure were generally lower than those of the short-lived radioiodine isotopes (132I and 133I) and their precursors (132Te). In other areas, the contributions of these two pathways were comparable to those of the short-lived radioiodines. For all subjects, intakes of 131I were the primary source of dose to the thyroid.     

Radionuclide concentrations in mule deer with reference to waste-management ponds on the Hanford Site

A comparison was made between the amount of time 17 radio-collared mule deer (Odocoileus hemionus) spent near low-level waste-management ponds on the Hanford Site and the levels of radionuclides found in samples of their muscle, liver, bone and rumen contents. All deer had low, but detectable, amounts of 137Cs in their muscle, liver and rumen contents and 90Sr in their bone. Several other radionuclides were detected in the rumen samples, but were apparently not incorporated into the muscle and liver tissue. There was a positive, significant correlation between the amount of time deer spent near the waste-management ponds and the levels of 137Cs in their muscle and liver and 90Sr in their bone. The concentrations of 137Cs in rumen samples did not appear to be related to the amount of time deer spent near waste-management ponds. The variability of 137Cs in muscle was higher in those deer living near the waste-management ponds than in individuals residing in areas remote from the ponds. In general, the levels of radionuclides in Hanford Site deer appear to be reduced from that observed in the 1960s.     

Ingestion pathway model developed for use with an acute atmospheric dose model at the Savannah River Site

AXAIRQ is a straight-line Gaussian plume dose model used for prospective accident assessment at the Savannah River Site and currently includes the following dose pathways: inhalation, ground shine, and plume shine. In the event of an accident, another possible pathway for dose would be through ingestion of locally produced contaminated foodstuffs. A model, AXINGST, has been developed that would incorporate this pathway. Currently available ingestion models were referenced as a basis for AXINGST. The model calculates an ingestion dose following an atmospheric release of radionuclides and includes site-specific variables where applicable. AXINGST estimates tritium vegetation concentrations that are within a factor of 20-40 of measured data during previous accidental releases at SRS.     

Examination of the impact of radioactive liquid effluent releases from the Rancho Seco Nuclear Power Plant

A project has been carried out by Oak Ridge National Laboratory (ORNL) to estimate the concentrations of radionuclides in the environment resulting from the release of radioactive materials in the liquid waste effluents from the Rancho Seco Nuclear Power Plant (RSNPP) and to estimate possible radiation doses to man resulting from current environmental concentrations. To accomplish the objectives of this project, ORNL staff members conducted an environmental sampling program around the plant site during November and December 1984. Elevated levels of some anthropogenic radionuclides were found in the immediate environment of the plant. This radioactive contamination occurs primarily along streams receiving effluent from the plant and in fields irrigated with water from these streams. The primary contaminants are 137Cs and 134Cs, with lesser amounts of 60Co and 58Co. The ingestion of fish was the single most important pathway identified in this analysis. However, all specific pathways of exposure and usage factors were not precisely known for a complete dose assessment of current and potential use of contaminated water and soil around the RSNPP. The liquid effluent radionuclide releases from the RSNPP pose no significant health hazard to persons living near the RSNPP.     

Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 3, results, variability, and uncertainty

This paper is Part 3 of a three-part series investigating effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. The radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I and (90)Sr-(90)Y. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. Part 1 reviewed, summarized, characterized, and grouped all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Part 2 described the methods used to organize the data collected in Part 1 and segregate it into the ages and genders defined by the study, including imputed missing values from the existing data, apportioned activity in bone, and imputed activity in hollow organ contents and the remainder of the body. This paper estimates equivalent dose rates to target tissues from source regions and maps target tissues to lists of tissues with International Commission on Radiation Protection (ICRP) tissue-weighting factors or to surrogate tissue regions when there is no direct match. Effective dose rates using ICRP tissue-weighting factors recommended in 1977, 1990, and 2007, are then calculated, and an upper bound of variability of the effective dose rate is estimated by calculating the average coefficients of variation (CV), assuming all variance is due to variability. Most of the data were for adult males, whose average effective dose rate is estimated to be 337 μSv y(-1) (CV = 0.65, geometric mean = 283 μSv y(-1), geometric standard deviation s(G) = 1.81) using 2007 ICRP tissue-weighting factors. This result is between the National Council on Radiation Protection and Measurements' 1987 estimate of 390 μSv y(-1) (using 1977 w(T)s) and its 2009 estimate of 285 μSv y(-1) (using 2007 w(T)s) and is higher than the United Nations Scientific Committee on the Effects of Atomic Radiation's 2000 estimate of 310 μSv y(-1) (using 1990 w(T)s). The methods and software developed for this project are sufficiently detailed and sufficiently general to be usable with autopsy data from any or all countries.     

Method for estimating ingestion doses to the public near the Savannah River site following an accidental atmospheric release

At the Savannah River Site, emergency response computer models are used to estimate dose following releases of radioactive materials to the environment. Downwind air and ground concentrations and their associated doses from inhalation and ground shine pathways are estimated. The emergency response model (PUFF-PLUME) uses real-time data to track either instantaneous (puff) or continuous (plume) releases. A site-specific ingestion dose model was developed for use with PUFF-PLUME that includes the following ingestion dose pathways pertinent to the surrounding Savannah River Site area: milk, beef, water, and fish. The model is simplistic and can be used with existing code output.     

Uncertainty in predictions of fallout radionuclides in foods and of subsequent ingestion

Uncertainty in predictions from the PATHWAY food-chain model was estimated using Monte Carlo simulation. Uncertainty estimates, measured by the geometric standard deviation (GSD), were obtained for median values of time-integrated concentrations of 131I, 136Cs, and 137Cs in foods and for the corresponding time-integrated intakes resulting from ingestion of all foods. The GSDs associated with a given food for the two short-lived radionuclides, 131I and 136Cs, were not significantly different, but they differed from the GSDs for the longer-lived radionuclide. The GSDs for integrated concentrations of radionuclides in milk varied with the time of year fallout was deposited, but uncertainty for nondairy products was relatively independent of the date of fallout deposition. The estimated GSDs were applied to other radionuclides of interest based on physical half-life and ranged from 1.7 to 2.7 for time-integrated intake across all foods for radionuclides with physical half-lives less than 30 d, from 1.8 to 2.3 for half-lives ranging from 30 to 500 d, and from 1.9 to 2.1 when half-lives were greater than 500 d.