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OBJECTIVES: The aim of this study was to estimate the prevalence of lens opacities among physicians occupationally exposed to radiation – overall and by occupational factors – and to assess the feasibility of a large-scale study for risk assessment. METHODS: Based on a nationwide registry of 1312 physicians, mostly radiologists with occupational exposure to ionizing radiation, 120 subjects were invited to participate, of which 59 (49%) consented. The inclusion criteria included (i) age 45–70 years, (ii) cumulative recorded radiation dose >10 mSv, and (iii) duration of work with dose monitoring >15 years. The participants completed a questionnaire regarding occupational history and other risk factors for lens opacities. A full ophthalmological examination was performed. Lenticular changes were graded using the Lens Opacities Classification System, version II (LOCS II), and the Nidek EAS–1000 Scheimpflug slit-imaging videophotography system. RESULTS: Lens opacities were detected in 42% [95% confidence interval (95% CI) 29–55] of the 57 physicians without prior cataract surgery. Nuclear opacities were found in 14% (95% CI 6–26), cortical in 7% (95% CI 2–19), and posterior subcapsular in 5% (95% CI 1–15) of the subjects. The prevalence of lens opacities increased with age, smoking, and cumulative recorded radiation dose. After controlling for age, gender, and smoking, the excess odds ratio for any lens opacity was 0.13 (95% CI -0.02–0.28) per 10 mSv of cumulative radiation dose. CONCLUSIONS: Our preliminary results show cortical and posterior subcapsular lens opacities among physicians exposed to occupational radiation, consistent with recent studies on low dose radiation exposure. A full study with an unexposed reference group for risk estimation is warranted.

Abstract Background The aim of the study was to evaluate the agreement between self-reported and operator-derived estimates of call time based on a three-month monitoring period, as well as the consistency of mobile phone use over time. Alternative approaches to improve participation in a cohort study of mobile phone users were also compared. Methods A total of 5,400 subjects were identified from network operators' subscriber databases for recruitment to the pilot study. Operator and questionnaire data were used to quantify mobile phone use. Operator data were available for a subset of the subjects for a three-month period in three consecutive years. We also evaluated the effect of the length of the questionnaire and one- or two-phase recruitment on participation. Results The average response rate for both questionnaires and recruitment procedures was 12%. The response rate was not affected by the length of the questionnaire or the recruitment method. Operator data were available for 83% of the participants for 2007, the first study year. The agreement between self-reported and operator-derived call times decreased with the level of use among intermediate and heavy mobile phone users. During 2007-2009, mobile phone use increased fairly constantly over time. Conclusions The agreement between self-reported mobile phone use and operator databases was moderate and overestimation of the call time by participants was common. A prospective cohort study would be feasible in Finland, although the potentially low participation rate would increase the resources required for recruitment.

The article focuses on a study which described the use of a compartmental model to predict uranium excretion in human hair for protracted ingestion of natural uranium in drinking water. It considers the case of several individuals from different households who were previously examined through the urine, hair and toenail samples they provided, which were obtained at the time when the study population consumed water from the drilled well. It also discusses the adoption of a biokinetic model for uranium based on the structure and growth behavior of human hair.

The 234U/238U ratio in water, hair and nails samples was determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and by alpha-spectrometry for the water samples only. A correlation of 0.99 was found between the two ICPMS methods and of 0.98 with alpha-spectrometry. The range of activity ratios was between 0.9 and 2.6 according to the MC-ICPMS measurements. The reproducibility of both ICPMS techniques was better than 4% for water samples containing 1 µg l-1 of uranium and a 234U/238U atom ratio of 54.9 × 10-6. Sample preparation for the ICPMS consisted of dilution of water samples containing >10 µg l-1 of uranium and measurement time was ~1 mm, while alpha-spectrometry involved pre-concentration and separation of the uranium and counting times of 1000 mm. [ABSTRACT FROM AUTHOR]

The isotopic ratio 234U/238U in drinking water and in hair, toenail, and urine samples from 45 individuals who consumed 0.2-2775 μg d-1 of uranium in their drinking water was determined using a multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS). The 234U/238U atom ratio in the water samples varied from 51 × 10-6 to 252 × 10-6 whereas in secular equilibrium (i.e., unity activity ratio) the ratio is 54.9 × 10-6. The correlation of the 234U/238U ratio between hair and nail samples was 0.98, and between hair and nails and urine the ratio was 0.91 and 0.89, respectively. The correlation of the ratio between water and the hair or nails was 0.97 but only 0.72 for water and urine, possibly due to spectral interferences. These results conclusively demonstrated that the uranium found in the bioassays can be traced to the drinking water, thus providing a direct link to the source of exposure. Hair may serve as an excellent indicator of occupational or environmental exposure to uranium and provide information regarding its source. Bioassay of hair is attractive as it is an effective bio-concentrator, samples can be easily stored, the concentration reflects an integrated value, and, finally, the measurement of the 234U/238U isotopic ratio in digested hair samples by MC-ICPMS is feasible and highly informative. Hair bioassay can also be used to assess exposure to depleted uranium long after the subjects have left the area suspected of contamination. [ABSTRACT FROM AUTHOR]

The concentration of uranium in urine, hair, and nails due to continuous exposure through ingestion of drinking water was studied. The study population consisted of 205 individuals living in 134 different households in southern Finland where drinking water is supplied from private drilled wells. The population was selected to include a broad range of uranium daily intake from drinking water (0.03-2,775 µg d-1). The uranium content in drinking water, urine (overnight collection), hair and nails was determined by ICPMS. Uranium in urine was corrected for the matrix effects by use of thallium as an internal standard and adjusted by creatinine normalization. Hair and toenail samples were rinsed to remove external contamination prior to acid digestion and analysis. The uranium content in all excretion pathways was correlated with the uranium intake, particularly at elevated levels (≥10 µg d-1) where drinking water was the major source of exposure to uranium. The median of the individual uranium absorption factors for urine, hair, and toenails were fu = 0.003, fh = 0.003, and fn = 4 × 10-5, respectively. The association between the different bioassays was examined. The absorption factor, f1, was calculated for the population with an intake above 10 µg d-1 and was below 0.01 for 72% of the study persons (range 0.0002 to 0.070). No statistically significant difference in 11 values was found between women and men. However, the absorption factor was higher among younger (<60 y) than older (≥60 y) subjects and among people with a lower exposure (below 100 µg d-1) than among those that ingest over 100 µg d-1. [ABSTRACT FROM AUTHOR]

The water from some drilled wells in southwest Finland contains higharsenic concentrations (min--max: 17--980 mu g/L). We analyzed inorganic arsenic (As-i) and organic arsenic (monomethylarsonate [MMA] anddimethylarsinate [DMA]) species in urine and conducted a clinical examination of current users (n = 35) and ex-users (n = 12) of such wells. Ex-users had ceased to use the water from the wells 2--4 months previously. Urinary arsenic species were also analyzed from persons whose drinking water contained less than 1 mu g/L of arsenic (controls,n = 9). The geometric means of the concentrations of total arsenic in urine were 58 mu g/L for current users, 17 mu g/L for ex-users, and5 mu g/L for controls. The excreted arsenic was associated with the calculated arsenic doses, and on average 63% of the ingested arsenic dose was excreted in urine. The ratios of MMA/DMA and As-i/As-tot (As-tot = As-i + MMA + DMA) in urine tended to be lower among the current users and in the higher exposure levels than in controls, suggesting that As-i was better methylated in current users. However, the differences were mainly explained by age; older persons were better methylators of inorganic arsenic than younger individuals. The arsenic content of hair correlated well with the past and chronic arsenic exposure; an increase of 10 mu g/L in the arsenic concentration of the drinking water or an increase of 10--20 mu g/day of the arsenic exposure corresponded to a 0.1 mg/kg increase in hair arsenic. The individualswere interviewed and complained of muscle cramps, mainly in the legs, and this was associated with elevated arsenic exposure. The presentstudy demonstrates that arsenic methylation has no threshold at these exposure levels. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to obtain information on the radon concentrations to which Finnish workers are exposed. Radon measurements were conducted as integrated measurements in 700 workplaces, supplemented by continuous radon measurements in 334 workplaces. The occupational radon concentration was calculated by multiplying the result of the integrated measurements by the seasonal correction factor and the ventilation correction factor (ratio between the working time and the full-time radon concentration obtained from continuous measurement). The annual radon concentration to which workers are exposed was weighted by the actual number of workers in each province. In addition, workers were divided into three main occupational categories (working mainly outdoors, underground, or indoors above ground). Probability distribution of the parameters affecting radon concentration levels were generated to calculate a probabilistic estimate of the number of workers exposed to excessive radon levels. With deterministic methods, the geometric and arithmetic mean radon concentrations in conventional, above-ground workplaces were 41 and 91 Bq m -3 , respectively. The estimated geometric and arithmetic mean annual radon concentrations that Finnish workers are exposed to were assessed as 19 and 33 Bq m -3 , respectively. The generic ventilation correction factor for workplaces was calculated as 0.87. Assessed with probabilistic methods, there are approximately 34,000 workers in Finland whose exposure to radon exceeds the reference level of 300 Bq m -3 . Although radon concentrations are generally low in Finnish workplaces, many workers are exposed to high levels of radon. Radon exposure in the workplace is the most common source of occupational radiation exposure in Finland., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Health Physics Society.)

Representative sampling of radon in indoor air is difficult because the concentration often exhibits unpredictable spatial and temporal variation. In workplaces, temporal variation may be rapid, and the minimum and maximum concentration can differ by a factor of 100. In this paper, we compare methods for assessing the radon concentration in workplaces utilising the results of an initial investigation with a track-etch detector and the results of an additional continuous measurement. The recommended method is as follows: the mean radon concentration during the working hours of 1 week, as well as the weekly mean, is calculated from the continuous measurement. The ratio between these mean concentrations is multiplied by the result from the track-etch detector. The coefficient of variation of this method is assessed as 19%. If the result of 1 week of continuous measurement is used alone, the coefficient of variation is assessed as 32%., (© The Author(s) 2021. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

From 1948 to 1954, the Atomic Bomb Casualty Commission conducted a study of pregnancy outcomes among births to atomic bomb survivors (Hiroshima and Nagasaki, Japan) who had received radiation doses ranging from 0 Gy to near-lethal levels. Past reports (1956, 1981, and 1990) on the cohort did not identify significant associations of radiation exposure with untoward pregnancy outcomes, such as major congenital malformations, stillbirths, or neonatal deaths, individually or in aggregate. We reexamined the risk of major congenital malformations and perinatal deaths in the children of atomic bomb survivors (n = 71,603) using fully reconstructed data to minimize the potential for bias, using refined estimates of the gonadal dose from Dosimetry System 2002 and refined analytical methods for characterizing dose-response relationships. The analyses showed that parental exposure to radiation was associated with increased risk of major congenital malformations and perinatal death, but the estimates were imprecise for direct radiation effects, and most were not statistically significant. Nonetheless, the uniformly positive estimates for untoward pregnancy outcomes among children of both maternal and paternal survivors are useful for risk assessment purposes, although extending them to populations other than the atomic bomb survivors comes with uncertainty as to generalizability., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.)

Radon measurements in Finnish underground mines were started in 1972. Since 1992, regular radon inspections by the competent authority have been carried out in all underground mines. During these inspections, several grab samples are taken from the air, which are later measured in the laboratory. This is a follow-up survey of radon concentrations in the air of the underground mines. The average radon concentrations in the mines between the years 2011 and 2019 varied from 90 to 1100 Bq m -3 . Overall, the occupational radon exposure in the Finnish underground mines has remained at a low level from the 1990s onwards. In recent years, high radon concentrations have been observed only in those mines where active mining has ceased. Compared to other recent studies in mines in other countries, radon concentrations in Finnish mines are approximately at the same level. Uncertainties relating to infrequent grab sampling have been recognised and the authority is now testing personal radon detectors that may be used for the exposure assessment in the future., (© 2021 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved.)

Background: Indoor radon exposure is the second leading cause of lung cancer. Finnish radiation legislation obligates employers to measure indoor radon concentrations in workplaces, including schools and daycare centers, if they are in radon prone areas. Surveillance campaigns were conducted to ensure that the required radon measurements were performed and to gain knowledge on current indoor radon levels in daycare centers and schools., Methods: Daycare centers located in the high-radon risk municipalities were identified. Schools where indoor radon level measurements were obligatory but not performed, were identified., Results: Indoor radon measurements were performed in 633 daycare centers where the mean radon concentration was 86 Bq/m 3 and the median 40 Bq/m 3 . The radon level was greater than 300 Bq/m 3 in 8% ( n = 49) of daycare centers. The radon measurements were performed in 1176 schools, which is 95% of the schools to be measured. The mean radon concentration was 82 Bq/m 3 and the median 41 Bq/m 3 . The radon levels were greater than 300 Bq/m 3 in 14% ( n = 169) of the schools., Conclusions: The systematic surveillance campaigns by the radiation protection authority were very efficient in order to ensure that the measurements are performed in schools and daycare centers. The campaigns also reduced the radon exposure of employees, children, and adolescents, where necessary.

Twenty-five years have passed since the Chernobyl accident, but its health consequences remain to be well established. Finland was one of the most heavily affected countries by the radioactive fallout outside the former Soviet Union. We analyzed the relation of the estimated external radiation exposure from the fallout to cancer incidence in Finland in 1988-2007. The study cohort comprised all ∼ 3.8 million Finns who had lived in the same dwelling for 12 months following the accident (May 1986-April 1987). Radiation exposure was estimated using data from an extensive mobile dose rate survey. Cancer incidence data were obtained for the cohort divided into four exposure categories (the lowest with the first-year committed dose <0.1 mSv and the highest ≥ 0.5 mSv) allowing for a latency of 5 years for leukemia and thyroid cancer, and 10 years for other cancers. Of the eight predefined cancer sites regarded as radiation-related from earlier studies, only colon cancer among women showed an association with exposure from fallout [excess rate ratio per increment in exposure category 0.06, 95% confidence interval (CI) 0.02-0.11]. No such effect was observed for men, or other cancer sites. Our analysis of a large cohort over two decades did not reveal an increase in cancer incidence following the Chernobyl accident, with the possible exception of colon cancer among women. The largely null findings are consistent with extrapolation from previous studies suggesting that the effect is likely to remain too small to be empirically detectable and of little public health impact.

Aim: We studied whether incidence of all cancer sites combined was associated with the radiation exposure due to fallout from the Chernobyl accident in Finland. An emphasis was on the first decade after the accident to assess the suggested "promotion effect"., Methods: The segment of Finnish population with a stable residence in the first post-Chernobyl year (2 million people) was studied. The analyses were based on a 250m × 250m grid squares covering all of Finland and all cancer cases except cancers of the breast, prostate and lung. Cancer incidence in four exposure areas (based on first-year dose due to external exposure <0.1 mSv, 0.1-1.3, 0.3-0.5, or ≥ 0.5 mSv) was compared before the Chernobyl accident (1981-1985) and after it (1988-2007) taking into account cancer incidence trends for a longer period prior to the accident (since 1966)., Results: There were no systematic differences in the cancer incidence in relation to radiation exposure in any calendar period, or any subgroup by sex or age at accident., Conclusion: The current large and comprehensive cohort analysis of the relatively low levels of the Chernobyl fallout in Finland did not observe a cancer promotion effect., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objectives: The aim of this study was to estimate the prevalence of lens opacities among physicians occupationally exposed to radiation - overall and by occupational factors - and to assess the feasibility of a large-scale study for risk assessment., Methods: Based on a nationwide registry of 1312 physicians, mostly radiologists with occupational exposure to ionizing radiation, 120 subjects were invited to participate, of which 59 (49%) consented. The inclusion criteria included (i) age 45-70 years, (ii) cumulative recorded radiation dose >10 mSv, and (iii) duration of work with dose monitoring >15 years. The participants completed a questionnaire regarding occupational history and other risk factors for lens opacities. A full ophthalmological examination was performed. Lenticular changes were graded using the Lens Opacities Classification System, version II (LOCS II), and the Nidek EAS-1000 Scheimpflug slit-imaging videophotography system., Results: Lens opacities were detected in 42% [95% confidence interval (95% CI) 29-55] of the 57 physicians without prior cataract surgery. Nuclear opacities were found in 14% (95% CI 6-26), cortical in 7% (95% CI 2-19), and posterior subcapsular in 5% (95% CI 1-15) of the subjects. The prevalence of lens opacities increased with age, smoking, and cumulative recorded radiation dose. After controlling for age, gender, and smoking, the excess odds ratio for any lens opacity was 0.13 (95% CI -0.02-0.28) per 10 mSv of cumulative radiation dose., Conclusions: Our preliminary results show cortical and posterior subcapsular lens opacities among physicians exposed to occupational radiation, consistent with recent studies on low dose radiation exposure. A full study with an unexposed reference group for risk estimation is warranted.

Background: Ore workers are conventionally monitored for exposure by measuring the uranium in their urine, but specific biomarkers of kidney damage still remain to be discovered. A recent toxicogenomics study allowed us to focus on osteopontin (OSTP) normally excreted in human urine and linked to mineral metabolism., Objectives: We examined the association between osteopontin and uranium exposure both in vitro, in a human kidney cell model, and in the urine of exposed individuals., Methods: OSTP was measured in supernatants of uranium-exposed HK2 cells to establish a dose-response curve and a time course experiment. Its role was studied through a gene extinction experiment. Uranium and OSTP were then monitored in the urine of exposed nuclear fuel industry workers and a chronically exposed population. These levels were compared with those found in a non-exposed population., Results: The study of HK2 cells indicated that OSTP secretion decreased after uranium exposure in a concentration and time dependent manner, but its suppression does not affect cell sensitivity to uranium. In spite of wide inter-individual variability, this parameter decreases also in human urine when urinary uranium exceeds 30 μg/L after an acute exposure, a value considered to be critical for kidney damage., Conclusion: This study reports how toxicogenomics can highlight putative toxicity biomarkers in an easy to access biological fluid. The decrease of urinary osteopontin in response to uranium exposure suggests kidney damage and would thus be complementary to current markers., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: The aim of the study was to evaluate the agreement between self-reported and operator-derived estimates of call time based on a three-month monitoring period, as well as the consistency of mobile phone use over time. Alternative approaches to improve participation in a cohort study of mobile phone users were also compared., Methods: A total of 5,400 subjects were identified from network operators' subscriber databases for recruitment to the pilot study. Operator and questionnaire data were used to quantify mobile phone use. Operator data were available for a subset of the subjects for a three-month period in three consecutive years. We also evaluated the effect of the length of the questionnaire and one- or two-phase recruitment on participation., Results: The average response rate for both questionnaires and recruitment procedures was 12%. The response rate was not affected by the length of the questionnaire or the recruitment method.Operator data were available for 83% of the participants for 2007, the first study year. The agreement between self-reported and operator-derived call times decreased with the level of use among intermediate and heavy mobile phone users. During 2007-2009, mobile phone use increased fairly constantly over time., Conclusions: The agreement between self-reported mobile phone use and operator databases was moderate and overestimation of the call time by participants was common. A prospective cohort study would be feasible in Finland, although the potentially low participation rate would increase the resources required for recruitment.

Objectives: People in the Arctic regions are one of the most heavily exposed population from the global fallout from atmospheric atomic bomb testing of the 1950s and 1960s due to their diet rich in reindeer meat in which radionuclides accumulate. We estimated the effect of the radioactive fallout and ethnicity on the cancer incidence in Northern Finland., Methods: A cohort of the Arctic population in Finland (n=34,653) was identified through the Population Register Centre with grouping by reindeer herding status, ethnicity and radiation exposure. Annual average radiation doses, based on (137)Cs whole-body measurements, were assigned by birth year, gender and reindeer herder status. Incident cancer cases of a priori selected cancer types in the study cohort during 1971-2005 were identified from the Finnish Cancer Registry., Results: A total of 2630 cancer cases were observed versus 3073 expected on the basis of incidence rates in Northern Finland (standardised incidence ratio (SIR) was 0.86 with 95% CI of 0.82 to 0.89). For the indigenous Sami people SIR was even lower, 0.60 (95% CI 0.50 to 0.71). None of the cancer sites was significantly associated with the lifetime cumulative radiation dose. The SIR for the combined group of radiation-related cancer sites increased with the cumulative radiation dose received before 15 years of age (p=0.004)., Conclusion: Despite the low overall cancer incidence in the Arctic population and ethnic Sami people in Finland and lack of association between the lifetime cumulative radiation exposure from global radioactive fallout and cancer incidence, we found some indication of an increased cancer risk associated with radiation exposure received during childhood. Potential underestimation and misclassification of the radiation dose may affect the results and the findings should be interpreted with caution.

We assessed a new approach for evaluating the glioma risk among users of mobile phones to focus on the part of the brain most heavily exposed to radiofrequency electromagnetic fields from mobile phones. The tumor midpoint was defined from radiological imaging. A case-case analysis with 99 gliomas was performed using logistic regression. The exposed cases were those with the tumor mid-point within 4.6 cm from the line between the mouth and the external meatus of the ear, representing the most likely location of the mobile phone (the source of exposure). Alternative analyses based on various indicators of mobile phone use as the outcome were also carried out. The majority of cases were regular mobile phone users. A slightly higher proportion of gliomas among mobile phone users than non-users occurred within 4.6 cm from the presumed location of the mobile phone (28% vs. 14%). Modestly elevated odds ratios were observed for several indicators of mobile phone use, but without an exposure gradient. The highest odds ratios were found for contralateral and short-term use. Our results, though limited by the small sample size, demonstrate that detailed information on tumor location allows evaluation of the risk related to the most heavily exposed part of the brain, representing direct evaluation of the possible local carcinogenic effects of the radiofrequency fields. However, field strength varies between users and over time also within a given anatomic site, due to the output power of the phone. Collaborative analysis of a larger sample is planned., ((c) 2009 Wiley-Liss, Inc.)

Case-control studies of mobile phones are commonly based on retrospective, self-reported exposure information, which are often characterized as involving substantial uncertainty concerning data validity. We assessed the validity of self-reported mobile phone use and developed a statistical model to account for the over-reporting of exposure. We collected information on mobile phone use from 70 volunteers using two sources of data: self-report in an interview and network operator records. We used regression models to obtain bias-corrected estimates of exposure. A correlation coefficient of 0.71 was obtained between the self-reported and the network operators' data on average calling time (log-transformed minutes per month). A simple linear regression model, where the duration of calls acquired from network operators is explained with the self-reported duration fitted the data reasonably well (adjusted R(2) 0.51). The constant term was 2.71 and the regression coefficient 0.49 (logarithmic scale). No significant improvement in the model fit was achieved by including potential predictors of accuracy in self-reported exposure estimates, such as the pattern of mobile phone use, the modality of response to the questionnaire or demographic characteristics. Overestimation in self-reported intensity of mobile phone use can be accounted for by the use of regression calibration. The estimates obtained in our study may not be applicable in other contexts, but similar methods could be used to reduce bias in other studies.

Water from bedrock frequently contains higher concentrations of natural radionuclides than water from other sources. Bladder and kidneys receive a radiation dose when radioactive isotopes are excreted into urine. The subjects for this case-cohort study were selected from all drilled wells users in Finland. The study comprised 61 bladder cancer and 51 kidney cancer cases diagnosed between 1981 and 1995, as well as a random sample of 274 reference persons, stratified by age and sex. The median activity concentrations of radon in drilled wells used by bladder and kidney cancer cases and the reference cohort were 170, 140, and 130 Bq/L, respectively. The radium concentration was 0.01 Bq/L for all groups and the uranium concentrations were 0.08, 0.07, and 0.06 Bq/L, respectively. The bladder cancer risks associated with radon, radium, and uranium activity concentrations in drinking water were 1.02 (0.68-1.54) per log(100 Bq of radon/L), 0.73 (0.21-2.50) per log(0.1 Bq of radium/L), and 0.77 (0.32-1.89) per log(1 Bq of uranium/L). The corresponding figures for kidney cancer were 0.81 (0.47-1.37), 0.12 (0.01-1.10), and 0.92 (0.36-2.35), respectively. In conclusion, even though ingested radionuclides from drilled wells are a source of radiation exposure, they are not associated with a substantially increased risk of bladder or kidney cancers in concentrations occurring in drilled wells.

The aim of the study was to assess whether radioactive fallout from the Chernobyl accident in 1986 influenced thyroid cancer incidence among children and adolescents in Finland. The population was divided into two: those with thyroid doses less than 0 6 mSv and above 0.6 mSv. Cumulative incidence of thyroid cancer was identified from the Finnish Cancer Registry from a population aged 0-20 years in 1986 with a total of 1,356,801 persons. No clear difference in underlying thyroid cancer incidences rates were found during the pre-Chernobyl period (1970-1985) (rate ratio RR 0.95, 95% confidence interval CI 0.81-1.10). During the post-Chernobyl period (1991-2003), thyroid cancer incidence was lower in the more exposed population than in the less exposed population (RR 0.76, 95% CI 0.59-0.98). Our results did not indicate any increase in thyroid cancer incidence related to exposure to radiation from the Chernobyl accident.

The (234)U/(238)U ratio in water, hair and nails samples was determined by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) and by alpha-spectrometry for the water samples only. A correlation of 0.99 was found between the two ICPMS methods and of 0.98 with alpha-spectrometry. The range of activity ratios was between 0.9 and 2.6 according to the MC-ICPMS measurements. The reproducibility of both ICPMS techniques was better than 4% for water samples containing 1 mug l(-1) of uranium and a (234)U/(238)U atom ratio of 54.9 x 10(-6). Sample preparation for the ICPMS consisted of dilution of water samples containing >10 microg l(-1) of uranium and measurement time was approximately 1 min, while alpha-spectrometry involved pre-concentration and separation of the uranium and counting times of 1,000 min.

The isotopic ratio (234)U/(238)U in drinking water and in hair, toenail, and urine samples from 45 individuals who consumed 0.2-2775 microg d(-1) of uranium in their drinking water was determined using a multi-collector inductively coupled plasma mass spectrometer (MC-ICPMS). The U/U atom ratio in the water samples varied from 51 x 10(-6) to 252 x 10(-6) whereas in secular equilibrium (i.e., unity activity ratio) the ratio is 54.9 x 10(-6). The correlation of the (234)U/(238)U ratio between hair and nail samples was 0.98, and between hair and nails and urine the ratio was 0.91 and 0.89, respectively. The correlation of the ratio between water and the hair or nails was 0.97 but only 0.72 for water and urine, possibly due to spectral interferences. These results conclusively demonstrated that the uranium found in the bioassays can be traced to the drinking water, thus providing a direct link to the source of exposure. Hair may serve as an excellent indicator of occupational or environmental exposure to uranium and provide information regarding its source. Bioassay of hair is attractive as it is an effective bio-concentrator, samples can be easily stored, the concentration reflects an integrated value, and, finally, the measurement of the (234)U/(238)U isotopic ratio in digested hair samples by MC-ICPMS is feasible and highly informative. Hair bioassay can also be used to assess exposure to depleted uranium long after the subjects have left the area suspected of contamination.

Very high concentrations of naturally occurring radionuclides are encountered in Finnish groundwaters and wells. Radon ingested through drinking water can cause considerable radiation to the stomach. We assessed the effect of natural uranium and other radionuclides in drinking water on the risk of stomach cancer. Subjects (n = 144,627) in the base cohort had lived outside the municipal tap water system during 1967-1980. A subcohort of 4,590 subjects was formed for use as a reference group by random sampling of the base cohort, with stratification by age and sex. Within the subcohort, 371 subjects had used drinking water from drilled wells prior to 1981. Stomach cancer cases within the subcohort were identified through a cancer registry, and cases using water from drilled wells were selected. Activity concentrations of radon, radium-226 and natural uranium in the drinking water were analyzed using radiochemical and alpha spectrometric methods. The median activity concentration of radon in well water was 130 Bq/l for both the 88 stomach cancer cases and the 274 subjects in the subcohort. Median radium concentrations were 0.007 Bq/l for cases and 0.010 Bq/l for the subcohort, with a median uranium concentration of 0.07 Bq/l for both groups. Risk of stomach cancer was not associated with exposure to radon or other radionuclides. The hazard ratio of stomach cancer was 0.68 for radon (95% CI 0.29-1.59 at 100 Bq/l water), 0.69 per Bq/1 for radium-226 (95% CI 0.33-1.47) and 0.76 per Bq/1 for uranium (95% CI 0.48-1.21). Our results do not indicate an increased risk of stomach cancer from ingestion of radon or other natural radionuclides through drinking water at these exposure levels.

Uranium accumulates in bone, affects bone metabolism in laboratory animals, and when ingested in drinking water increases urinary excretion of calcium and phosphate, important components in the bone structure. However, little is known about bone effects of ingested natural uranium in humans. We studied 146 men and 142 women 26-83 years of age who for an average of 13 years had used drinking water originating from wells drilled in bedrock, in areas with naturally high uranium content. Biochemical indicators of bone formation were serum osteocalcin and amino-terminal propeptide of type I procollagen, and a marker for bone resorption was serum type I collagen carboxy-terminal telopeptide (CTx). The primary measure of uranium exposure was uranium concentration in drinking water, with additional information on uranium intake and uranium concentration in urine. The data were analyzed separately for men and women with robust regression (which suppresses contributions of potential influential observations) models with adjustment for age, smoking, and estrogen use. The median uranium concentration in drinking water was 27 microg/L (interquartile range, 6-116 microg/L). The median of daily uranium intake was 36 microg (7-207 microg) and of cumulative intake 0.12 g (0.02-0.66 g). There was some suggestion that elevation of CTx (p = 0.05) as well as osteocalcin (p = 0.19) could be associated with increased uranium exposure (uranium in water and intakes) in men, but no similar relationship was found in women. Accordingly, bone may be a target of chemical toxicity of uranium in humans, and more detailed evaluation of bone effects of natural uranium is warranted.

Animal studies and small studies in humans have shown that uranium is nephrotoxic. However, more information about its renal effects in humans following chronic exposure through drinking water is required. We measured uranium concentrations in drinking water and urine in 325 persons who had used drilled wells for drinking water. We measured urine and serum concentrations of calcium, phosphate, glucose, albumin, creatinine, and beta-2-microglobulin to evaluate possible renal effects. The median uranium concentration in drinking water was 28 microg/L (interquartile range 6-135, max. 1,920 microg/L) and in urine 13 ng/mmol creatinine (2-75), resulting in the median daily uranium intake of 39 microg (7-224). Uranium concentration in urine was statistically significantly associated with increased fractional excretion of calcium and phosphate. Increase of uranium in urine by 1 microg/mmol creatinine increased fractional excretion of calcium by 1.5% [95% confidence interval (CI), 0.6-2.3], phosphate by 13% (1.4-25), and glucose excretion by 0.7 micromol/min (-0.4-1.8). Uranium concentrations in drinking water and daily intake of uranium were statistically significantly associated with calcium fractional excretion, but not with phosphate or glucose excretion. Uranium exposure was not associated with creatinine clearance or urinary albumin, which reflect glomerular function. In conclusion, uranium exposure is weakly associated with altered proximal tubulus function without a clear threshold, which suggests that even low uranium concentrations in drinking water can cause nephrotoxic effects. Despite chronic intake of water with high uranium concentration, we observed no effect on glomerular function. The clinical and public health relevance of the findings are not easily established, but our results suggest that the safe concentration of uranium in drinking water may be within the range of the proposed guideline values of 2-30 microg/L.