Past and present levels of some radionuclides in fish from Bikini and Enewetak Atolls

Long-term radiological assessment of a Mediterranean freshwater ecosystem surrounding a nuclear power plant

The radionuclide concentration of man-made radionuclides on non-human biota in freshwater ecosystems has been extensively studied in environments affected by the Chernobyl and Fukushima accidents, in both humid continental and subtropical climates, respectively. However, there are very few studies that assess the long-term effects of operating nuclear facilities in Mediterranean environments. In the present study, a temporal analysis of the impact on carp, cattail, and bulrushes in the cooling pond of the currently operating Almaraz nuclear power plant was investigated for the period 2000-2020. The results do not show a general trend in man-made radionuclide concentrations. Instead, depending on their availability and the type of organism, trends decrease over time. This is also reflected in the effective half-lives obtained, which are lower than the physical half-life for some radionuclides. Transfer coefficients for the main man-made radionuclides detected were obtained, and it was found that these were significantly lower than the typical ranges found for benthic fish and vascular plants in freshwater ecosystems. Finally, the internal and external doses received by the carp have been evaluated using ERICA tool, and it has been observed that the main contribution to the total dose is due to the internal dose (0.65-7.04) × 10-4 µGy/h.

Inequities in Access to Medical Care Among Adults Diagnosed with Diabetes: Comparisons Between the US Population and a Sample of US-Residing Marshallese Islanders

OBJECTIVE

We examined barriers to accessing medical care for migrant US-residing Marshallese Islanders.

METHODS

Cross-sectional analyses were conducted to identify potential inequities. Surveys from largely migrant diabetic Marshallese Islanders (n = 255) were compared with nationally representative data. Two major outcomes were assessed including 1-whether or not one reported having forgone medical care in the past year because of cost-and 2-whether or not one reported not having a usual source of care.

RESULTS

Overall, 74% and 77% of Marshallese Islanders reported forgone care and no usual source of care, respectively, versus 15% and 7% of the US diabetic population. In multivariable analyses, being younger; uninsured; unemployed; male; of lower education; Native American or Hispanic (versus White); and residing in the South were associated with forgone care nationwide, whereas only lacking insurance was associated with forgone care among Marshallese Islanders. Nationwide being younger; uninsured; unmarried; female; of lower education; Native American or Hispanic (versus White); and residing in the South were associated with not having a usual source of care, whereas only being younger and uninsured were associated with not having a usual source of care among Marshallese Islanders.

CONCLUSION

The largest group of diabetic Marshallese Islanders in the continental US faces severe healthcare access inequities necessitating policies that increase access to health insurance options and associated resources.

Radionuclides in sea turtles at the Montebello Islands former nuclear test sites: Current and historical dose rates for adults and embryos

Radionuclides from 1950s weapons testing at the Montebello Islands, Western Australia, may impact sea turtle embryos incubating within eggs laid in contaminated sands or be taken up into adult body tissues where they can contribute to radiation dose over a turtles' 60+ year lifespan. We measured plutonium in all local samples including turtle skin, bones, hatchlings, eggshells, sea sediments, diet items and beach sands. The amount of Pu in developing embryos/hatchling samples was orders of magnitude lower than that in the surrounding sands. These contaminated sands caused most dose to eggs (external dose from ¹³⁷Cs, ¹⁵²Eu), while most of the dose to adults was from internalised radionuclides (98%). While current dose rates are relatively low, local dose rates were high for about ten years following the 1950s detonations and may have resulted in lethality or health impacts to a generation of turtles that likely carry biomarkers today.

Plutonium and other radionuclides persist across marine-to-terrestrial ecotopes in the Montebello Islands sixty years after nuclear tests

Since the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg^-1 of ^239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their ^240/239Pu and ^241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms.

How stakeholder engagement influenced a randomized comparative effectiveness trial testing two Diabetes Prevention Program interventions in a Marshallese Pacific Islander Community

BACKGROUND

Marshallese face significant health disparities, with particularly high rates of type 2 diabetes. Engaging stakeholders in the research process is essential to reduce health inequities.

METHODS

A community- and patient-engaged research approach was used to involve community Marshallese stakeholders in a randomized comparative effectiveness trial testing two Diabetes Prevention Program interventions.

RESULTS

The article outlines the engagement process and the specific influence that stakeholders had on the research planning and implementation, discussing the areas of agreement and disagreement between community and patient stakeholders and academic investigators and documenting changes to the research protocol.

CONCLUSION

The article provides an example of methods that can be used to design and conduct a randomized controlled trial testing with a population who has been underrepresented in research and suffered significant historical trauma.

Design of a randomized, controlled, comparative-effectiveness trial testing a Family Model of Diabetes Self-Management Education (DSME) vs. Standard DSME for Marshallese in the United States

BACKGROUND

Type 2 diabetes (T2D) is a significant public health problem, with U.S. Pacific Islander communities-such as the Marshallese-bearing a disproportionate burden. Using a community-based participatory approach (CBPR) that engages the strong family-based social infrastructure characteristic of Marshallese communities is a promising way to manage T2D.

OBJECTIVES

Led by a collaborative community-academic partnership, the Family Model of Diabetes Self-Management Education (DSME) aimed to change diabetes management behaviors to improve glycemic control in Marshallese adults with T2D by engaging the entire family.

DESIGN

To test the Family Model of DSME, a randomized, controlled, comparative effectiveness trial with 240 primary participants was implemented. Half of the primary participants were randomly assigned to the Standard DSME and half were randomly assigned to the Family Model DSME. Both arms received ten hours of content comprised of 6-8 sessions delivered over a 6-8 week period.

METHODS

The Family Model DSME was a cultural adaptation of DSME, whereby the intervention focused on engaging family support for the primary participant with T2D. The Standard DSME was delivered to the primary participant in a community-based group format. Primary participants and participating family members were assessed at baseline and immediate post-intervention, and will also be assessed at 6 and 12 months.

SUMMARY

The Family Model of DSME aimed to improve glycemic control in Marshallese with T2D. The utilization of a CBPR approach that involves the local stakeholders and the engagement of the family-based social infrastructure of Marshallese communities increase potential for the intervention's success and sustainability.

Measurement of background gamma radiation in the northern Marshall Islands

We report measurements of background gamma radiation levels on six islands in the northern Marshall Islands (Enewetak, Medren, and Runit onEnewetak Atoll; Bikini and Nam on Bikini Atoll; and Rongelap on Rongelap Atoll). Measurable excess radiation could be expected from the decay of (137)Cs produced by the US nuclear testing program there from 1946 to 1958. These recordings are of relevance to safety of human habitation and resettlement. We find low levels of gamma radiation for the settled island of Enewetak [mean = 7.6 millirem/year (mrem/y) = 0.076 millisievert/year (mSv/y)], larger levels of gamma radiation for the island of Rongelap (mean = 19.8 mrem/y = 0.198 mSv/y), and relatively high gamma radiation on the island of Bikini (mean = 184 mrem/y = 1.84 mSv/y). Distributions of gamma radiation levels are provided, and hot spots are discussed. We provide interpolated maps for four islands (Enewetak, Medren, Bikini, and Rongelap), and make comparisons to control measurements performed on the island of Majuro in the southern Marshall Islands, measurements made in Central Park in New York City, and the standard agreed upon by the United States and the Republic of the Marshall Islands (RMI) governments (100 mrem/y = 1 mSv/y). External gamma radiation levels on Bikini Island significantly exceed this standard (P = <<0.01), and external gamma radiation levels on the other islands are below the standard. To determine conclusively whether these islands are safe for habitation, radiation exposure through additional pathways such as food ingestion must be considered.

Effect of US health policies on health care access for Marshallese migrants

The Republic of the Marshall Islands is a sovereign nation previously under the administrative control of the United States. Since 1986, the Compacts of Free Association (COFA) between the Republic of the Marshall Islands and the United States allows Marshall Islands citizens to freely enter, lawfully reside, and work in the United States, and provides the United States exclusive military control of the region. When the COFA was signed, COFA migrants were eligible for Medicaid and other safety net programs. However, these migrants were excluded from benefits as a consequence of the Personal Responsibility and Work Opportunity Reconciliation Act. Currently, COFA migrants have limited access to health care benefits in the United States, which perpetuates health inequalities.

Radiological dose rates to marine fish from the Fukushima Daiichi accident: the first three years across the North Pacific

A more complete record is emerging of radionuclide measurements in fish tissue, sediment, and seawater samples from near the Fukushima Daiichi Nuclear Power Plant (FDNPP) and across the Pacific Ocean. Our analysis of publicly available data indicates the dose rates to the most impacted fish species near the FDNPP (median 1.1 mGy d(-1), 2012-2014 data) have remained above benchmark levels for potential dose effects at least three years longer than was indicated by previous, data-limited evaluations. Dose rates from (134,137)Cs were highest in demersal species with sediment-associated food chains and feeding behaviors. In addition to (134,137)Cs, the radionuclide (90)Sr was estimated to contribute up to approximately one-half of the total 2013 dose rate to fish near the FDNPP. Mesopelagic fish 100-200 km east of the FDNPP, coastal fish in the Aleutian Islands (3300 km), and trans-Pacific migratory species all had increased dose rates as a consequence of the FDNPP accident, but their total dose rates remained dominated by background radionuclides. A hypothetical human consumer of 50 kg of fish, gathered 3 km from the FDNPP in 2013, would have received a total committed effective dose of approximately 0.95 mSv a(-1) from combined FDNPP and ambient radionuclides, of which 0.13 mSv a(-1) (14%) was solely from the FDNPP radionuclides and below the 1 mSv a(-1) benchmark for public exposure.

Effective half-life of caesium-137 in various environmental media at the Savannah river site

During the operational history of the Savannah River Site (SRS), many different radionuclides have been released from site facilities into the SRS environment. However, only a relatively small number of pathways, most importantly (137)Cs in fish and deer, have contributed significantly to doses and risks to the public. The "effective" half-lives (Te) of (137)Cs (which include both physical decay and environmental dispersion) in Savannah River floodplain soil and vegetation and in fish and white-tailed deer from the SRS were estimated using long-term monitoring data. For 1974-2011, the Tes of (137)Cs in Savannah River floodplain soil and vegetation were 17.0 years (95% CI = 14.2-19.9) and 13.4 years (95% CI = 10.8-16.0), respectively. These Tes were greater than in a previous study that used data collected only through 2005 as a likely result of changes in the flood regime of the Savannah River. Field analyses of (137)Cs concentrations in deer collected during yearly controlled hunts at the SRS indicated an overall Te of 15.9 years (95% CI = 12.3-19.6) for 1965-2011; however, the Te for 1990-2011 was significantly shorter (11.8 years, 95% CI = 4.8-18.8) due to an increase in the rate of (137)Cs removal. The shortest Tes were for fish in SRS streams and the Savannah River (3.5-9.0 years), where dilution and dispersal resulted in rapid (137)Cs removal. Long-term data show that Tes are significantly shorter than the physical half-life of (137)Cs in the SRS environment but that they can change over time. Therefore, it is desirable have a long period of record for calculating Tes and risky to extrapolate Tes beyond this period unless the processes governing (137)Cs removal are clearly understood.

Spatial distribution of organochlorine contaminants in soil, sediment, and fish in Bikini and Enewetak Atolls of the Marshall Islands, Pacific Ocean

Several nuclear tests were performed at Enewetak and Bikini Atolls in the Marshall Islands between 1946 and 1958. The events at Bikini Atoll involved several ships that were tested for durability during nuclear explosions, and 24 vessels now rest on the bottom of the Bikini lagoon. Nine soil samples were collected from different areas on the two islands of the atoll, and eighteen sediment, nine fish, and one lobster were collected in the vicinity of the sunken ships. Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polychlorinated terphenyls (PCTs) in these samples were analyzed using gas chromatography/ion trap mass spectrometry (GC/ITMS). The average recoveries ranged from 78% to 104% for the different PCB congeners. The limits of detection (LOD) for PCBs, PCTs, DDE, DDT, and dieldrin ranged 10-50 pg g(-1). Some fish from Enewetak contained PCBs at a concentration range of 37-137 ng g(-1), dry weight (dw), and most of the soils from Enewetak showed evidence of PCBs (22-392 ng g(-1)dw). Most of the Bikini lagoon sediment samples contained PCBs, and the highest was the one collected from around the Saratoga, an aircraft carrier (1555 ng g(-1)dw). Some of the fish samples, most of the soil samples, and only one of the sediment samples contained 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) and PCBs. In addition to PCBs, the soils from Enewetak Atoll contained PCTs. PCTs were not detected in the sediment samples from Bikini Atoll. The results suggest local pollution sources of PCBs, PCTs, and OCPs.

Concentrations of 137Cs, 90Sr, 108m Ag, 239+240 Pu and atom ratio of 240Pu/239Pu in tanner crabs, Chionoecetes japonicus and Chionoecetes opilio collected around Japan

The anthropogenic radionuclides, (137)Cs, (90)Sr, (108m)Ag, (239+240)Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996-2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of (240)Pu/(239)Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet.

Detection and temporal variation of (60)Co in the digestive glands of the common octopus, Octopus vulgaris, in the East China Sea

(60)Co were detected in common octopus specimens collected in the East China Sea in 1996-2005. The source of (60)Co has remained unclear yet. Stable isotope analyses showed that there was no difference in stable Co concentrations between octopus samples with (60)Co and without (60)Co. This result showed that the stable Co in the digestive gland of octopus potentially did not include a trace amount of (60)Co and the source of (60)Co existed independently. Furthermore, investigations of octopus in other area and other species indicated that the origin of the source of (60)Co occurred locally in the restricted area in the East China Sea and not in the coastal area of Japan. Concentrations of (60)Co have annually decreased with shorter half-life than the physical half-life. This decrease tendency suggests that the sources of (60)Co were identical and were temporary dumped into the East China Sea as a solid waste.

Acute and chronic intakes of fallout radionuclides by Marshallese from nuclear weapons testing at Bikini and Enewetak and related internal radiation doses

Annual internal radiation doses resulting from both acute and chronic intakes of all important dose-contributing radionuclides occurring in fallout from nuclear weapons testing at Bikini and Enewetak from 1946 through 1958 have been estimated for the residents living on all atolls and separate reef islands of the Marshall Islands. Internal radiation absorbed doses to the tissues most at risk to cancer induction (red bone marrow, thyroid, stomach, and colon) have been estimated for representative persons of all population communities for all birth years from 1929 through 1968, and for all years of exposure from 1948 through 1970. The acute intake estimates rely on a model using, as its basis, historical urine bioassay data, for members of the Rongelap Island and Ailinginae communities as well as for Rongerik residents. The model also utilizes fallout times of arrival and radionuclide deposition densities estimated for all tests and all atolls. Acute intakes of 63 radionuclides were estimated for the populations of the 20 inhabited atolls and for the communities that were relocated during the testing years for reasons of safety and decontamination. The model used for chronic intake estimates is based on reported whole-body, urine, and blood counting data for residents of Utrik and Rongelap. Dose conversion coefficients relating intake to organ absorbed dose were developed using internationally accepted models but specifically tailored for intakes of particulate fallout by consideration of literature-based evidence to choose the most appropriate alimentary tract absorption fraction (f1) values. Dose estimates were much higher for the thyroid gland than for red marrow, stomach wall, or colon. The highest thyroid doses to adults were about 7,600 mGy for the people exposed on Rongelap; thyroid doses to adults were much lower, by a factor of 100 or more, for the people exposed on the populated atolls of Kwajalein and Majuro. The estimates of radionuclide intake and internal radiation dose to the Marshallese that are presented in this paper are the most complete available anywhere and were used to make projections of lifetime cancer risks to the exposed populations, which are presented in a companion paper in this volume.

Radiation doses for Marshall Islands Atolls affected by U.S. nuclear testing: all exposure pathways, remedial measures, and environmental loss of (137)Cs

Radiation doses calculated for people resettling Bikini Island at Bikini Atoll, Enjebi Island at Enewetak Atoll, Rongelap Island at Rongelap Atoll, and Utrōk Island at Utrōk Atoll are presented. Residence is assumed to begin in 2010. In previous dose assessments it was shown that (137)Cs accounts for about 98% of the total dose for returning residents. About 85 to 90% (depending on the atoll) is via consumption of locally grown foods containing (137)Cs, and about 10 to 15% is due to external exposure from (137)Cs in the soil. These assessments were made using only the radiological half-life of (137)Cs (30.1 y). We have shown since that there is an environmental loss of (137)Cs from soil to groundwater that results in a more rapid loss of (137)Cs from the atoll ecosystem. The mean effective half-life of (137)Cs at the atolls is 8.5 y. Moreover, treatment of coconut trees with potassium (K) reduces (137)Cs concentration in drinking coconut meat at Bikini Atoll to about 5% of pretreatment concentrations. The magnitude of reduction is dependent on the concentration of (137)Cs in soil, and thereby in food crops, and is less for Enjebi and Rongelap Islands than for Bikini Island. Treatment of food crops and fruit trees with K and removal of the top 15 cm of soil around houses and community buildings prior to construction to reduce external exposure where people spend most of their time has been presented to the communities as a "Combined Option" remediation strategy. Doses presented here are calculated using the Combined Option, effective half-life of (137)Cs at the atolls, and a diet of both imported and local foods. The average natural background dose in the Marshall Islands, plus the anthropogenic nuclear test-related dose at Bikini, Enjebi, and Rongelap Islands, is less for each of the islands than the average background dose in the U.S. and Europe.

Changes in 137Cs concentrations in soil and vegetation on the floodplain of the Savannah River over a 30 year period

(137)Cs released during 1954-1974 from nuclear production reactors on the Savannah River Site, a US Department of Energy nuclear materials production site in South Carolina, contaminated a portion of the Savannah River floodplain known as Creek Plantation. (137)Cs activity concentrations have been measured in Creek Plantation since 1974 making it possible to calculate effective half-lives for (137)Cs in soil and vegetation and assess the spatial distribution of contaminants on the floodplain. Activity concentrations in soil and vegetation were higher near the center of the floodplain than near the edges as a result of frequent inundation coupled with the presence of low areas that trapped contaminated sediments. (137)Cs activity was highest near the soil surface, but depth related differences diminished with time as a likely result of downward diffusion or leaching. Activity concentrations in vegetation were significantly related to concentrations in soil. The plant to soil concentration ratio (dry weight) averaged 0.49 and exhibited a slight but significant tendency to decrease with time. The effective half-lives for (137)Cs in shallow (0-7.6 cm) soil and in vegetation were 14.9 (95% CI=12.5-17.3) years and 11.6 (95% CI=9.1-14.1) years, respectively, and rates of (137)Cs removal from shallow soil and vegetation did not differ significantly among sampling locations. Potential health risks on the Creek Plantation floodplain have declined more rapidly than expected on the basis of radioactive decay alone because of the relatively short effective half-life of (137)Cs.

Bikini Atoll coral biodiversity resilience five decades after nuclear testing

Five decades after a series of nuclear tests began, we provide evidence that 70% of the Bikini Atoll zooxanthellate coral assemblage is resilient to large-scale anthropogenic disturbance. Species composition in 2002 was assessed and compared to that seen prior to nuclear testing. A total of 183 scleractinian coral species was recorded, compared to 126 species recorded in the previous study (excluding synonomies, 148 including synonomies). We found that 42 coral species may be locally extinct at Bikini. Fourteen of these losses may be pseudo-losses due to inconsistent taxonomy between the two studies or insufficient sampling in the second study, however 28 species appear to represent genuine losses. Of these losses, 16 species are obligate lagoonal specialists and 12 have wider habitat compatibility. Twelve species are recorded from Bikini for the first time. We suggest the highly diverse Rongelap Atoll to the east of Bikini may have contributed larval propagules to facilitate the partial resilience of coral biodiversity in the absence of additional anthropogenic threats.

Radionuclides in marine fishes and birds from Amchitka and Kiska Islands in the Aleutians: establishing a baseline

Amchitka Island (51degrees N lat, 179 degrees E long) was the site of three underground nuclear tests from 1965-1971. There have been no substantive studies of radionuclides in marine fishes and birds in the area since the mid-1970's. In this study, levels of 60Co, 52Eu, 90Sr, 99Tc, 129I, 137Cs, and the actinides (241Am, 238Pu, 239,240Pu, 234U, 235U, 236U, and 238U) were studied in ten marine fish species (including Pacific Cod Gadus macrocephalus and Pacific Halibut Hippoglossus stenolepis) and five marine bird species (including Glaucous-winged Gulls Larus glaucescens, Tufted Puffins Fratercula cirrhata, and Common Eider Ducks Somateria mollissima) from Amchitka. The same species were collected at a reference site, Kiska Island (52 degrees N lat; 177 degrees E long), about 130 km west of Amchitka. Each sample was a composite of edible muscle from five or more individual fish or birds of similar size (+/-15%) from the same sampling station. The null hypotheses of no differences among species or between Amchitka and Kiska were tested. Most analytic results were below the minimum detectable activity (MDA), even when 1,000 g sizes and 72 h counting times were used. The only radionuclides detected above the MDA were 137Cs, 241Am, 239,240Pu, 234U, 235U, and 238U. There were significant differences in 137Cs as a function of species, but not location, for top predatory fishes. Of the fishes, eight of ten species had 137Cs values above the MDA for some samples; only one bird, Glaucous-winged Gull, had 137Cs values above the MDA. The highest concentrations of 137Cs were in Dolly Varden [Salvelinus malma, 0.780 (Bq kg(-1) wet weight)] and Pacific Cod (0.602 Bq kg(-1)). In aggregate for any actinides, 73 of 234 (31%) composites for fish were above the MDA, compared to only 3 of 98 (3%) for birds. 234U and 238U, radionuclides that are primarily natural in origin, were routinely detected in these biological samples, but there were no significant differences in mean concentrations between Amchitka and Kiska. The concentrations of all radionuclides examined at Amchitka are similar to those of other uncontaminated Northern Hemisphere sites, and are lower than those reported for fishes and birds from the Irish Sea in the vicinity of the Sellafield nuclear reprocessing facility, an area with known contamination.

Potential of largemouth bass as vectors of 137Cs dispersal

We conducted a radio telemetry study on the movements of potentially contaminated largemouth bass between Steel Creek, a restricted access (137)Cs contaminated stream on the Savannah River Site (located in South Carolina, USA), and the publicly accessible Savannah River. Largemouth bass were relatively mobile in lower Steel Creek and the portion of the Savannah River near Steel Creek, and there was considerable movement between these two habitats. Largemouth bass had home ranges of about 500 linear meters of shoreline in the Savannah River but sometimes moved long distances. Such movements occurred primarily during the spawning season, largely upstream, and increased when water levels were changing or elevated. However, approximately 90% of the largemouth bass observations were within 10 km of Steel Creek. The total quantity of (137)Cs transported into the Savannah River by largemouth bass was much less than transported by water and suspended sediments discharged from Steel Creek. We conclude that largemouth bass from the Savannah River Site are unlikely to be responsible for long distance dispersal of substantial radiological contamination in the Savannah River.

Uptake of 137Cs by fresh water fish

The uptake and discharge rates of 137Cs by fresh water fish at different radionuclide concentrations have been studied. A dual compartment model was used to fit the experimental data. The discharge rates have been found to be negligible for the duration of the experiment of 10 d. The uptake rates were independent of radionuclide concentrations for a particular type of fresh water fish and were different for different types of fish. The uptake rates of carp, tilapia and snakehead were 1.58, 1.66 and 2.23, in unit of 10(-6) h-1, respectively. It was also estimated that the consumption of fresh water fish, even if the water were contaminated as much as that in the Chernobyl accident, leads to negligible latent cancer fatality to the Hong Kong population.

239 + 240Pu and 137Cs concentrations in fish, cephalopods, crustaceans, shellfish, and algae collected around the Japanese coast in the early 1990s

Marine organisms, i.e. fish, cephalopods, crustaceans, shellfish, and algae, were collected in the early 1990s along the Sea of Japan coast and the Japanese Pacific coast and analyzed for their 239 + 240Pu and 137Cs concentrations. The 239 + 240Pu concentrations in muscle of fish were below 0.4 mBq/kg wet wt. and the lowest among the analyzed marine organisms. Most 137Cs concentrations in muscle of fish ranged from 100 to 300 mBq/kg wet wt. Higher concentrations of 239 + 240Pu, ranging from 1.6 to 5.7 mBq/kg wet wt., were observed in viscera of cephalopods than in their muscle. The 239 + 240Pu concentrations in whole soft tissues of bivalves varied approximately one order of magnitude from 0.8 to 6.1 mBq/kg wet wt., while 137Cs concentrations had little variation, being approximately 60 mBq/kg wet wt. The 239 + 240Pu concentrations in algae had a wide variation, ranging from 1.7 to 42.3 mBq/kg wet wt., and were higher than those of the other marine organisms. No statistically significant difference in mean concentrations of 239 + 240Pu was detected among the whole soft tissues of bivalves, viscera of cephalopods and crustaceans, and whole bodies of cephalopods and crustaceans within the 95% confidence limit. The mean concentrations of 137Cs became higher in the order, cephalopods and crustaceans and bivalves, algae, viscera of fish, muscles of fish. The mean concentrations of 239 + 240Pu were comparable for algae collected along the Japan Sea coast and the Pacific coast. Furthermore, the difference in mean concentrations of 137Cs in algae between the Japan Sea coast and the Pacific coast was not statistically significant within the 95% confidence limit. These results can be considered to indicate no definite influence from radioactive dumping into the Japan Sea by the former USSR and Russia with respect to radioactive pollution of marine organisms collected along the Japanese coast.

Radionuclide characterization and associated dose from long-lived radionuclides in close-in fallout delivered to the marine environment at Bikini and Enewetak Atolls

Between June 1946 and October 1958, Enewetak and Bikini Atolls were used by the US as testing grounds for 66 nuclear devices. The combined explosive yield from these tests was 107 million t (million t TNT equivalents). This testing produced close-in fallout debris that was contaminated with quantities of radioactive fission and particle activated products, and unspent radioactive nuclear fuel that entered the aquatic environment of the atolls. Today, the sediments in the lagoons are reservoirs for tens of TBq of the transuranics and some long-lived fission and activation products. The larger amounts of contamination are associated with fine and coarse sediment material adjacent to the locations of the high yield explosions. Radionuclides are also distributed vertically in the sediment column to various depths in all regions of the lagoons. Concentrations greater than fallout background levels are found in filtered water sampled over several decades from all locations and depths in the lagoons. This is a direct indication that the radionuclides are continuously mobilized to solution from the solid phases. Of particular importance is the fact that the long-lived radionuclides are accumulated to different levels by indigenous aquatic plants and organisms that are used as food by resident people. One might anticipate finding continuous high contamination levels in many of the edible marine organisms from the lagoons, since the radionuclides associated with the sediments are not contained and are available to the different organisms in a relatively shallow water environment. This is not the case. We estimate that the radiological dose from consumption of the edible parts of marine foods at Enewetak and Bikini is presently approximately 0.05% of the total 50-year integral effective dose from all other exposure pathways that include ingestion of terrestrial foods and drinking water, external exposure and inhalation. The total radiological dose from the marine pathway is dominated by the natural radionuclides, 210Po and 210Pb. Man-made radionuclides presently contribute < 0.3% of the dose from these natural radionuclides in the marine food chain and within approximately 90 years only 0.15%.