Internal Radiation Exposure Research Articles

Childhood Thyroid Cancers and Radioactive Iodine Therapy: Necessity of Precautious Radiation Health Risk Management

One of the lessons from Chernobyl's legacy on health impact beyond 20 years is not only how to detect and treat the patients with radiation-associated thyroid cancers but how to follow up those who received radioactive iodine treatment repetitively after surgery in order to monitor any recurrence/worsening and also how to predict the risk of secondary primary cancers for their lifetime period. To evaluate the possibility of second primary tumors after radioactive iodine treatment, we reviewed the reports on risks from both external and internal radiation exposure, especially at high doses during childhood through an internet service of the National Library of Medicine and the National Institutes of Health, PubMed by the end of June, 2007, together with our own experience of Chernobyl childhood thyroid cancers. Children who were internally exposed after Chernobyl accident have a long-term risk of well differentiated thyroid cancers. Once they have disease, ironically radioactive iodine ablation is one of the useful therapies after surgical treatment. Elevated risks of solid cancers and leukemia have been found in radioiodine-treated patients, however, so far precious few reports from Chernobyl thyroid cancer patient were published. To reduce the adverse effects of radioactive iodine therapy on non-target tissues, recombinant human TSH has been applied and proved effective. Period of latency of second primary cancers may be very long. Therefore patients treated with high activities of radioactive iodine, especially children cases, should be carefully followed up during their whole lifespan.

Cardiovascular Diseases in Women. Why Now?

Few studies have been undertaken to measure indoor thoron concentration in Indian dwellings. The distribution pattern of thoron inside room conditions is complex due to short half-life. The internal radiation exposure due to inhalation of indoor thoron and decay products can be quite large near to the wall. In this work, Computational Fluid Dynamics (CFD) technique was utilized for prediction of indoor thoron concentration and distribution pattern. Thoron flux was measured experimentally to be used as input and CFD runs were performed for closed and open room conditions. Thoron concentration inside the room was also experimentally measured using Scintillation Thoron Monitor, STM (active) and pin-hole dosimeters (passive). For open room conditions, thoron concentration was found to be smaller and relatively homogenous compared to closed room conditions. CFD predictions were found to be reasonably matching with active and passive results. A separate profile experiment increased confidence towards validation of CFD for indoor thoron distribution (prediction) applications. CFD can be used as a tool to predict thoron concentration and its distribution in indoor conditions.

Chromosomal aberration analysis in lymphocytes from workers exposed to I-131 in nuclear medicine departments in Iran

In order to evaluate the cytogenetic effects of low doses of radiation by internal or external exposure to iodine-131, we analysed chromosomal aberrations (CA) in peripheral blood lymphocytes from 34 subjects working in the nuclear medicine departments in Iran. The studied groups consisted of 26 individuals (Group A) who were employed in these centres without any evidence of radiation exposure by physical dosimeters or whole body counting, and 8 workers who were suspected to be exposed chronically to low doses of radiation from iodine-131. The results revealed that the mean frequency of CA in group A was not significantly increased compared with the control group (P = 0.21), while in group B the differences were statistically significant (P < 0.05). Moreover, these cytogenetic findings showed chromosome damage depended on internal or external radiation exposures but did not show its relation to the duration of work.

Lung cancer mortality among workers at a nuclear materials fabrication plant

The Oak Ridge, Tennessee Y-12 plant has operated as a nuclear materials fabrication plant since the 1940s. Given the work environment, and prior findings that lung cancer mortality was elevated among white male Y-12 workers relative to US white males, we investigated whether lung cancer mortality was associated with occupational radiation exposures. A cohort of 3,864 workers hired between 1947 and 1974 who had been monitored for internal radiation exposure was identified. Vital status was ascertained through 1990. Over the study period 111 lung cancer deaths were observed. Cumulative external radiation dose under a 5-year lag assumption was positively associated with lung cancer mortality (0.54% increase in lung cancer mortality per 10 mSv, se=0.16, likelihood ratio test (LRT)=5.84, 1 degree of freedom [df]); cumulative internal radiation dose exhibited a highly-imprecise negative association with lung cancer mortality. The positive association between external radiation dose and lung cancer mortality was primarily due to exposure occurring in the period 5-14 years after exposure (0.97% increase in lung cancer mortality rate per 10 mSv, se=0.28, LRT=6.35, 1 df). The association between external radiation dose and lung cancer mortality was negative for exposures occurring at ages<35 years and positive for exposures occurring at ages 35-50 and 50+years. There is evidence of a positive association between cumulative external radiation dose and lung cancer mortality in this population. However, a causal interpretation of this association is constrained by the uncertainties in external and internal radiation dose estimates, the lack of information about exposures to other lung carcinogens, and the limited statistical power of the study.

The Techa River Cohort: Study Design and Follow-up Methods

Residents living on the banks of the Techa River in the Southern Urals region of Russia were exposed to radioactive contamination from the Mayak plutonium production and separation facility that discharged liquid radioactive waste into this river. This paper describes the methods used to establish and follow the Extended Techa River Cohort (ETRC), which includes almost 30,000 people living along the Techa River who were exposed to a complex mixture of radionuclides, largely 90Sr and 137Cs. The system of regular follow-up allows ascertainment of vital status, cause of death and cancer incidence. With over 50 years of follow-up and over 50% deceased, the ETRC now provides a valuable opportunity to study a wide range of health effects, both early and late, associated with protracted internal and external radiation exposures. The wide range of doses allows analysis of the nature of the dose-response relationship based on internal comparisons. Other features of the cohort are the high proportion (40%) exposed under age 20, and the inclusion of both sexes. The limitations of the study include loss to follow-up due to difficulties in tracing some cohort members and migration and incomplete ascertainment of cause of death.

Chelating Agents Used for Plutonium and Uranium Removal in Radiation Emergency Medicine

The prospects of using chelating agents for increasing the excretion of actinides are reviewed. The removal of plutonium by chelating agents is of great importance because plutonium is extremely dangerous and induces cancer due to radiation toxicity. Similarly, uranium is a radionuclide, which causes severe renal dysfunction within a short time period due to chemical toxicity. It may also induce cancers such as leukemia and osteosarcoma in cases of long-term internal radiation exposure. Investigations on chelating agents for the removal of plutonium were initiated in the 1960's and 1970's. Diethylenetriaminepentaacetic acid (DTPA) is recognized as a chelating agent that accelerates the excretion of plutonium in early treatment after an accident. Thereafter, there has long been an interest in finding new chelating agents with radionuclide removal properties for use in therapy, and many chelating agents such as 3,4,3-LIHOPO and CBMIDA have been studied for their ability to remove plutonium and uranium. Recently, the focus has turned to drugs that have been used successfully in the treatment of a variety of other diseases, for example the iron chelating drug deferiprone or 1,2-dimethyl-3-hydroxypyrid-4-one (L1), which is used in thalassaemia and ethane-1-hydroxy-1,1-bisphosphonate (EHBP), which is used in osteoporosis. Within this context, it is important to examine the clinical use of these two drugs as well as the properties of the experimental chelators 3,4,3-LIHOPO and CBMIDA in order to identify possible uses in the treatment of radiation workers contaminated with plutonium and uranium.

Measurement of the whole-body 137Cs in residents around the Chernobyl nuclear power plant

To understand the current situation of internal radiation exposure in the population around the Chernobyl Nuclear Power Plant (CNPP), we examined the 137Cs body burden in six residents of Belarus, Ukraine and Russia in 2002 and 2004 using the whole-body counter (WBC) at Nagasaki University (Japan). The data were compared with those of our previous study performed in 1993-1994 using the same method. In 2002 and 2004, peaks of 137Cs were detected in two residents from Gomel, which was heavily contaminated by the CNPP accident, one from Minsk (Belarus) and one from Kiev (Ukraine), but another resident from Minsk showed no 137Cs peaks. The results of the present study suggests that residents around the CNPP are still exposed to chronic 137Cs internal irradiation, probably due to the daily consumption of contaminated domestic foods, but the risk of any disease by the irradiation is quite low. Long-term follow-up of WBC around the CNPP is useful and may contribute to radiation safety regulation together with a reduction of unnecessary radiophobia for the residents.

MEDICAL AID AND RESEARCH PROJECTS FROM NAGASAKI ON RADIATION HEALTH EFFECTS AROUND CHERNOBYL

The medical cooperative projects from Nagasaki to the former USSR have been performed in mainly two regions: Chernobyl and Semipalatinsk since 1990 and 1995, respectively. What we should do here in Nagasaki and also from Nagasaki will be discussed at the standpoint of humanitarian medical aid and scientific research collaboration usinsgt different channels of governmental and non-governmental cooperative linkages. The 21st Center of Excellence (COE) program of «International Consortium for Medical Care of Hibakusha and Radiation Life Science» established in Nagasaki University can serve our knowledge and experience much more directly in relation to the radiocontaminated areas in the world, and indeed contribute to the lessons learned from Chernobyl and also to the newly establishme of Network of Excellence (NOE) for Radiation Emergency Medicine under the auspices of the WHO-REMPAN. Within the frame of the International Consortium of Radiation Research, a molecular epidemiology of thyroid diseases has now been conducted in our departments. The clue of radiation-associated thyroid carcinogenesis may give us a new concept on experimental and epidemiological approaches to low dose radiation effects on human health, including internal radiation exposure.

Current situation and future planning of molecular epidemiology of radiation health effects around Chernobyl and Semipalatinsk

The medical cooperative projects from Nagasaki University to the former USSR have been performed in mainly two regions: Chernobyl and Semipalatinsk since 1990 and 1995, respectively. What we should do here in Nagasaki and also from Nagasaki will be discussed from the standpoint of humanitarian medical aid and scientific research collaboration using different channels of governmental and nongovernmental cooperative linkages. The 21st Century Center of Excellence (COE) program of “International Consortium for Medical Care of Hibakusha and Radiation Life Science” newly established in Nagasaki University can serve our knowledge and experience much more directly in relation to the radiocontaminated areas in the world, and indeed contribute to the lessons learned from Chernobyl and also to the future planning of the Network of Excellence (NOE) for Radiation Emergency Medical Preparedness and Assistance under the auspices of the WHO-REMPAN. Within the frame of the International Consortium of Radiation Research, a molecular epidemiology of thyroid diseases has now been conducted in our departments in addition to international medical assistance. The clue of radiation-associated thyroid carcinogenesis may give us a new concept on experimental and epidemiological approaches to low-dose radiation effects on human health, including internal radiation exposure.

40 YEARS OF FOLLOW-UP IN THE SEMIPALATINSK HISTORICAL COHORT STUDY

The aim of the collaborative study is to contribute to the assessment and documentation of long term health effects, primarily cancer, due to local fallout from atmospheric nuclear weapons testing conducted between 1949 and 1962 at the Semipalatinsk test site (STS), Kazakhstan. The Semipalatinsk cohort study had been set up already in the 1960s comprises follow-up information for an exposed and a comparison group of a total of 19,545 people. Cohort members include inhabitants of ten highly exposed settlements adjacent to the STS during the period of atmospheric nuclear weapons testing at STS and six settlements in the Kokpektinsky rayon of the Semipalatinskaya oblast which can be considered as virtually non (or very low) exposed group. For both groups, follow-up data were included from 1960 to end of 1999. A preliminary individual dose estimation due to external and internal radiation exposure was conducted by SRIRME. It took into account technical details of the nuclear device, meteorological data at time of the test, place of residence, and age at exposure of each person. The estimated mean dose in the exposed group was 640 mSv. Cause of death data were obtained based on death registration acts. Relative risks in terms of age-adjusted rate ratios were calculated as measures of effect. When comparing exposed and non-exposed group, overall rate ratios of 2.42 (2.10; 2.80)95%CI for mortality due to all solid tumours were found. For men and women, the rate ratios are 2.21 (1.84; 2.65) 95%CI and 2.79 (2.22; 3.51) 95%CI, respectively. The obtained results suggest significant increases in cancer mortality in the exposed group. Although dose estimates require further validation and refinement, the data from the Semipalatinsk historical cohort study remain a valuable source of information for radiation risk estimates relevant for radiation protection and the follow-up of the cohorts should be continued and extended in future. The results indicate the importance of further epidemiological investigation in order to address both the local lack of information and related health care issues.

Studies of strontium biokinetics in humans. Part 2: uptake of strontium from aqueous solutions and labelled foodstuffs.

The accidental release of radioactive isotopes of strontium, mainly (90)Sr, into the environment and its transfer into the biosphere results in an internal radiation exposure of the affected population. In order to obtain reliable estimates of the committed dose due to an intake of Sr radionuclides, reliable information on its metabolic behaviour inside the human body is needed, i.e. biokinetic data on fractional uptake from contaminated foodstuffs, distribution to and retention in different organs and tissues of the human body. Such information can be obtained by tracer kinetic investigations. The committed effective dose is dependent on the fractional intestinal absorption of the ingested activity (f(1) value). The International Commission on Radiological Protection in its publication ICRP 67 adopted an f(1) value of 0.3 for adults. This study is aimed at investigating if the value corresponds with the actual uptake from contaminated foodstuffs. Aqueous solutions and contaminated vegetables, i.e. cress and salad (lettuce) were used as test materials. For this purpose, the methodology for intrinsic labelling of foodstuffs described in part 1 was applied. For aqueous solutions, a mean f(1) value of 0.63+/-0.14 (mean +/- SD) was obtained by administering 1 mg of strontium. The uptake of Sr from cress intrinsically labelled with about 1 mg Sr almost corresponds to that from aqueous solutions (f(1)=0.62+/-0.10), but from lettuce it is reduced by a factor of 2 (f(1)=0.27+/-0.08).

The Effects of Internal Radiation Exposure on Cancer Mortality in Nuclear Workers at Rocketdyne/Atomics International

We examined the effects of chronic exposure to radionuclides, primarily uranium and mixed-fission products, on cancer mortality in a retrospective cohort study of workers enrolled in the radiation-monitoring program of a nuclear research and development facility. Between 1950 and 1994, 2,297 workers were monitored for internal radiation exposures, and 441 workers died, 134 (30.4%) of them from cancer as the underlying cause. We calculated internal lung-dose estimates based on urinalysis and whole-body and lung counts reported for individual workers. We examined cancer mortality of workers exposed at different cumulative lung-dose levels using complete risk-set analysis for cohort data, adjusting for age, pay type, time since first radiation monitored, and external radiation. In addition, we examined the potential for confounding due to chemical exposures and smoking, explored whether external radiation exposure modifies the effects of internal exposure, and estimated effects after excluding exposures likely to have been unrelated to disease onset. Dose-response relations were observed for death from hemato- and lymphopoietic cancers and from upper aerodigestive tract cancers, adjusting for age, time since first monitored, pay type, and external (gamma) radiation dose. No association was found for other cancers, including cancers of the lung. Despite the small number of exposed deaths from specific cancer types and possible bias due to measurement error and confounding, the positive findings and strong dose-response gradients observed suggest carcinogenic effects of internal radiation to the upper aerodigestive tract and the blood and lymph system in this occupational cohort. However, causal inferences require replication of our results in other populations or confirmation with an extended follow-up of this cohort.

External radiation exposure and mortality in a cohort of uranium processing workers.

In a study of 2,514 White male workers employed between 1942 and 1966 at a US uranium processing plant, mortality was compared with overall US mortality, and the relation between external ionizing radiation and cancer was evaluated. Through 1993, 1,013 deaths occurred. The mean cumulative dose was 47.8 mSv. The standardized mortality ratio (SMR) was 0.90 for all causes of death and 1.05 for all cancers. Many cancer sites had elevated SMRs. Among nonmalignant outcomes, the SMR for chronic nephritis was 1.88 (six deaths observed). An excess relative risk estimate of 10.5 per Sv (10 cases) was observed for kidney cancer; this may have resulted from chance, internal radiation, or chemical exposures not considered.

The effects of internal radiation exposure on cancer mortality in nuclear workers at Rocketdyne/Atomics International.

We examined the effects of chronic exposure to radionuclides, primarily uranium and mixed-fission products, on cancer mortality in a retrospective cohort study of workers enrolled in the radiation-monitoring program of a nuclear research and development facility. Between 1950 and 1994, 2,297 workers were monitored for internal radiation exposures, and 441 workers died, 134 (30.4%) of them from cancer as the underlying cause. We calculated internal lung-dose estimates based on urinalysis and whole-body and lung counts reported for individual workers. We examined cancer mortality of workers exposed at different cumulative lung-dose levels using complete risk-set analysis for cohort data, adjusting for age, pay type, time since first radiation monitored, and external radiation. In addition, we examined the potential for confounding due to chemical exposures and smoking, explored whether external radiation exposure modifies the effects of internal exposure, and estimated effects after excluding exposures likely to have been unrelated to disease onset. Dose-response relations were observed for death from hemato- and lymphopoietic cancers and from upper aerodigestive tract cancers, adjusting for age, time since first monitored, pay type, and external (gamma) radiation dose. No association was found for other cancers, including cancers of the lung. Despite the small number of exposed deaths from specific cancer types and possible bias due to measurement error and confounding, the positive findings and strong dose-response gradients observed suggest carcinogenic effects of internal radiation to the upper aerodigestive tract and the blood and lymph system in this occupational cohort. However, causal inferences require replication of our results in other populations or confirmation with an extended follow-up of this cohort.

Assessment of exposure of miners to the α-rays of long-lived radionuclides associated with respirable ore dust in the Jaduguda U mine

The present work is intended to quantify the locational and operational internal exposures of workers due to the α-rays of long-lived radionuclides associated with the airborne respirable particulate in the underground U mine at Jaduguda. The concentrations of the dust and the α-rays of the long-lived radionuclides in the mine air are log-normally distributed with respective geometric means ( χ g) of 0.49 mg m −3 and 21.25 mBq m −3 and geometric standard deviations ( σ g) of 1.7 and 1.88, respectively. There exists a moderately positive linear correlation (correlation coefficient=0.43) between the dust and the activity concentrations. The α-activity of the long-lived radionuclides in respirable dust, measured radiometrically, assumes a χ g of 41.73 Bq g −1 with a σ g of 1.98 which is in close correspondence with the analytically evaluated value for the U mill tailings sand of identical particle size range. The internal radiation exposure was estimated to be only about 5% of the annual effective dose limit.

Natural radioactivity found in bioassay measurements / Natürliche Radioaktivität in Bioassay-Messungen (Ausscheidungsmessungen)

The internal radiation exposure of occupationally exposed persons in nuclear facilities is checked regularly for internal contamination by bioassay measurements. Although these persons are generally not involved in any incident, natural radioactivity from U, Th and Ra can be found in their urine or faeces. Uranium has been found with no particular ratio between 234 U and 238 U. 230 Th, 228 Th and sometimes 232 Th have also been detected. 228 Th has generally been found in excess of 232 Th. All these measurements were performed by alpha spectrometry. The few 226 Ra results have been measured using the Lucas or emanation method.

The Effects of Internal Radiation Exposure on Cancer Mortality in Nuclear Workers at Rocketdyne/Atomics International

The Effects of Internal Radiation Exposure on Cancer Mortality in Nuclear Workers at Rocketdyne/Atomics International

Setting standards for the safe level of radioactive contamination of water and bottom sediments in bodies of water

In this paper, we propose standards which can be used to simply and reliably monitor the content of technogenic radioactive substances in rivers and other bodies of water. We introduce the concept of “maximum safe concentration” and “reference monitored concentration” of radionuclides in water, and also the “maximum concentration of radionuclides in bottom sediments.” To determine the maximum safe concentration of radionuclides in water, we have used the basic public health principle established in NRB-96: to not exceed the limit of an effective dose of 1 mSv/y for external and internal radiation exposure for a critical population group, considering overall water use. To define the degree of radioactive contamination of the bottom of bodies of water, we propose using the maximum concentration of radionuclides in bottom sediments: a concentration less than that for which the bottom sediments may be classified in the category of “low activity solid radioactive wastes” according to OSP-72/87. We offer a calculation scheme and numerical values for the proposed standards for some radionuclides most frequently encountered in practice and examples of their use.

Liquid scintillation measurement of40K for the education on radioactivity

Liquid scintillation counting of40K in ordinary potassium propionate is a highly suitable experimental task in the general education on radioactivity. The counting efficiency is about 90%, depending little on the measurement conditions. Potassium propionate is of suitable properties and can be easily obtained commercially or by conversion from other compounds. The result of counting, about 1,700 cpm/g, is highly impressive to many students, indicating the existence of40K radioactivity unexpectedly high in the normal nature, and can be used for the exercise of calculating our internal radiation exposure.

Radioiodine-induced thyroid cancer: Studies in the aftermath of the accident at Chernobyl

While a great deal is known about the relationship between external radiation exposure and thyroid cancer, much less is known about the oncogenic effects of internal radiation exposure from isotopes of iodine. The accident at the Chernobyl nuclear power plant released massive quantities of radioiodine isotopes into the atmosphere. The large number of ensuing thyroid cancers in exposed children leaves little doubt that these malignancies have occurred as a result of the accident. However, carefully planned epidemiological studies are needed to confirm that these are due predominantly to I-131 exposure, to determine the dose-response relationship, to monitor for continuing effects and to evaluate other contributing factors. Preliminary evidence indicates that there is a distinct pattern of somatic genetic changes in the thyroid cancers from the Chernobyl area.