Industrial Radiographers Research Articles

Improving the industrial defect recognition in radiographic testing by pre-training on medical radiographs

Deep learning methodologies have gained substantial traction for defect recognition in industrial radiographic testing including welds, castings and other fields. Regardless of the deep learning utilized, it has emerged as a standard configuration to use a model pre-trained from ImageNet to accelerate convergence and enhance recognition accuracy. However, there is a significant gap between the domain of natural images and industrial radiographs, raising the question of whether there might be a superior pre-training method than relying on ImageNet pre-training. Fortunately, medical radiographs are more similar to industrial radiographs than natural images because of the same imaging method. In this paper, we initially utilize numerous medical radiographic images from CheXpert dataset to train a pre-trained CNN model. Then, we apply this model to four distinct tasks within two radiographic testing scenarios to validate its advantages and generalization capabilities. Finally, experiments on multiple datasets indicate that our method brings more benefits than ImageNet pre-training or training from scratch, with a F1 score improvement of 3.41 %–13.72 % for defect classification and a mIoU improvement of 1.05 %–6.58 % for defect segmentation. It demonstrates that pre-training from medical radiographs provides a cost-free improvement for all kinds of tasks in industrial defect recognition.

Moon, Mars and Minds: Evaluating Parkinson’s disease mortality among U.S. radiation workers and veterans in the million person study of low-dose effects

BackgroundRadiation is one of the most important stressors related to missions in space beyond Earth’s orbit. Epidemiologic studies of exposed workers have reported elevated rates of Parkinson’s disease. The importance of cognitive dysfunction related to low-dose rate radiation in humans is not defined. A meta-analysis was conducted of six cohorts in the Million Person Study (MPS) of low-dose health effects to learn whether there is consistent evidence that Parkinson’s disease is associated with radiation dose to brain. Materials and methodsThe MPS evaluates all causes of death among U.S. radiation workers and veterans, including Parkinson’s disease. Systematic and consistent methods are applied to study all categories of workers including medical radiation workers, industrial radiographers, nuclear power plant workers, atomic veterans, and Manhattan Projects workers at the Los Alamos National Laboratory and at Rocky Flats. Consistent methods for all cohorts are used to estimate organ-specific doses and to obtain vital status and cause of death. ResultsThe meta-analysis include 6 cohorts within the MPS, consisting of 517,608 workers and 17,219,001 person-years of observation. The mean dose to brain ranged from 6.9 to 47.6 mGy and the maximum dose from 0.76 to 2.7 Gy. Five of the 6 cohorts revealed positive associations with Parkinson’s disease. The overall summary estimate from the meta-analysis was statistically significant based on 1573 deaths due to Parkinson’s disease. The summary excess relative risk at 100 mGy was 0.17 (95% CI: 0.05; 0.29). ConclusionsParkinson’s disease was positively associated with radiation in the MPS cohorts indicating the need for careful evaluation as to causality in other studies, delineation of possible mechanisms, and assessing possible implications for space travel as well as radiation protection guidance for terrestrial workers.

Cataractogenic Effects щf Low-Dose Radiation цith Low Let: More not Than There. Report 2. Epidemiological Studies

Radiation damage to the lens is considered to be the third most important effect of radiation, after mortality from cancer and diseases of the circulatory system (ICRP-118). In terms of the effects of low dose radiation with low LET (up to 100 mGy), interest in the problem of cataractogenic disorders is growing, although there is no clarification of the issue. In the present study, two reports attempt to fill this gap. Report 1 reviewed the work on cataractogenic effects of the lowest doses of radiation with low LET in experiments in vitro and in vivo and concluded that there was no significant confirmation of them in animal experiments; Report 2 presents the results of epidemiological studies relevant to the problem. Data are presented on the uncertainties associated with such epidemiological studies: the ambiguity of the relationship between disorders in the lens and the formation of cataracts, their dependence on age, as well as the dependence of the estimation on the accepted system for classifying opacities. These uncertainties have had the consequence that since 1977 the ICRP has proposed five successively decreasing threshold doses (limits) for lens disorders. The dose patterns for radiogenic damage to the lens in the nine exposed groups mentioned in the reviews are considered: victims of atomic bombings (LSS), liquidators of the Chernobyl accident, medical radiologists (rentgenologists, technologists), patients after computed tomography and radiotherapy, industrial radiographers, nuclear industry workers, residents living with an increased radiation background (natural and man-made), for cosmonauts/astronauts and pilots. For some groups, there were statements about the effects of low doses of radiation, however, the presence of a number of epidemiological uncertainties (reverse causality in diagnostic exposure, the contribution of radiation with high LET, UV and solar radiation in cosmonauts/astronauts and pilots, doses above 100 mGy for the upper limit of the studied range in residents, etc.) do not allow us to consider these statements as proven. Therefore, for most exposed groups, a threshold of 300 mGy should be adhered to, regardless of acute or chronic exposure, according to ICRP-118, although due to the precautionary principle, based on the data discussed in Reports 1 and 2, the limit can be reduce to 200 mGy. Exceptions are medical radiologists (rentgenologists, technologists) and industrial radiographers, for whom the cataractogenic effects of low doses (several tens of milligray; working minimum – 20 mGy) can be real. This is probably due to the direct involvement of the organ of vision in professional manipulations with radiation. It is concluded that it is expedient to limit ourselves to these two groups in the future when studying radiogenic disorders in the lens after exposure to low doses of low-LET radiation, while the other groups are unpromising in this regard.

Organ dose reconstruction for the radiation epidemiological study of Korean radiation workers: The first dose evaluation for the Korean Radiation Worker Study (KRWS)

The Korea Institute of Radiological and Medical Sciences has started a radiation epidemiological study, titled "Korean Radiation Worker Study," to evaluate the health effects of occupational exposure to radiation. As a part of this study, we investigated the methodologies and results of reconstructing organ-specific absorbed doses based on personal dose equivalent, Hp(10), reported from 1984 to 2019 for 20,605 Korean radiation workers. For the organ dose reconstruction, representative exposure scenarios (i.e., radiation energy and exposure geometry) were first determined according to occupational groups, and dose coefficients for converting Hp(10) to organ absorbed doses were then appropriately taken based on the exposure scenarios. Individual annual doses and individual cumulative doses were reconstructed for 27 organs, and the highest values were observed in the thyroid doses (on average 0.77 mGy/y and 10.47 mGy, respectively). Mean values of individual cumulative absorbed doses for the red bone marrow, colon, and lungs were 7.83, 8.78, and 8.43 mSv, respectively. Most of the organ doses were maximum for industrial radiographers, followed by nuclear power plant workers, medical workers, and other facility workers. The organ dose database established in this study will be utilized for organ-specific risk estimation in the Korean Radiation Worker Study.

Application of a semi-automated dicentric scoring system in triage and monitoring occupational radiation exposure.

The dicentric chromosome assay (DCA) is considered the gold standard for radiation biodosimetry, but it is limited by its long dicentric scoring time and need for skilled scorers. The automation of scoring dicentrics has been considered a strategy to overcome the constraints of DCA. However, the studies on automated scoring methods are limited compared to those on conventional manual DCA. Our study aims to assess the performance of a semi-automated scoring method for DCA using ex vivo and in vivo irradiated samples. Dose estimations of 39 blind samples irradiated ex vivo and 35 industrial radiographers occupationally exposed in vivo were estimated using the manual and semi-automated scoring methods and subsequently compared. The semi-automated scoring method, which removed the false positives of automated scoring using the dicentric chromosome (DC) scoring algorithm, had an accuracy of 94.9% in the ex vivo irradiated samples. It also had more than 90% accuracy, sensitivity, and specificity to distinguish binary dose categories reflecting clinical, diagnostic, and epidemiological significance. These data were comparable to those of manual DCA. Moreover, Cohen's kappa statistic and McNemar's test showed a substantial agreement between the two methods for categorizing in vivo samples into never and ever radiation exposure. There was also a significant correlation between the two methods. Despite of comparable results with two methods, lower sensitivity of semi-automated scoring method could be limited to assess various radiation exposures. Taken together, our findings show the semi-automated scoring method can provide accurate dose estimation rapidly, and can be useful as an alternative to manual DCA for biodosimetry in large-scale accidents or cases to monitor radiation exposure of radiation workers.

Mortality from leukemia, cancer and heart disease among U.S. nuclear power plant workers, 1957–2011

Background The aim of the Million Person Study of Low-Dose Health Effects (MPS) is to examine the level of radiation risk for chronic exposures received gradually over time and not acutely as was the case for the Japanese atomic bomb survivors. Nuclear power plant (NPP) workers comprise nearly 15 percent of the MPS. Leukemia, selected cancers, Parkinson’s disease, ischemic heart disease (IHD) and other causes of death are evaluated. Methods and material The U.S. Nuclear Regulatory Commission’s Radiation Exposure Information and Reporting System (REIRS) and the Landauer, Inc. dosimetry databases identified 135,193 NPP workers first monitored 1957–1984. Annual personal dose equivalents [Hp(10)] were available for each worker. Radiation records from all places of employment were sought. Vital status was determined through 2011. Mean absorbed doses to red bone marrow (RBM), esophagus, lung, colon, brain and heart were estimated by adjusting the recorded Hp(10) for each worker by scaling factors, accounting for exposure geometry and energy of the incident gamma radiation. Standardized mortality ratios (SMR) were calculated. Radiation risks were estimated using Cox proportional hazards models. Results Nearly 50% of workers were employed for more than 20 years. The mean duration of follow-up was 30.2 y. Overall, 29,124 total deaths occurred, 296 from leukemia other than chronic lymphocytic leukemia (CLL), 3382 from lung cancer, 140 from Parkinson’s disease and 5410 from IHD. The mean dose to RBM was 37.9 mGy (maximum 1.0 Gy; percent >100 mGy was 9.2%), 43.2 mGy to lung, 43.7 mGy to colon, 33.2 mGy to brain, and 43.9 mGy to heart. The SMRs (95% CI) were 1.06 (0.94; 1.19) for leukemia other than CLL, 1.10 (1.07; 1.14) for lung cancer, 0.90 (0.76; 1.06) for Parkinson’s disease, and 0.80 (0.78; 0.82) for IHD. The excess relative risk (ERR) per 100 mGy for leukemia other than CLL was 0.15 (90% CI −0.001; 0.31). For all solid cancers the ERR per 100 mGy (95% CI) was 0.01 (–0.03; 0.05), for lung cancer −0.04 (–0.11; 0.02), for Parkinson’s disease 0.24 (–0.02; 0.50), and for IHD −0.01 (–0.06; 0.04). Conclusion Prolonged exposure to radiation increased the risk of leukemia other than CLL among NPP workers. There was little evidence for a radiation association for all solid cancers, lung cancer or ischemic heart disease. Increased precision will be forthcoming as the different cohorts within the MPS are combined, such as industrial radiographers and medical radiation workers who were assembled and evaluated in like manner.

Interventional radiologists have a higher rate of chromosomal damage due to occupational radiation exposure: a dicentric chromosome assay.

There are growing concerns regarding radiation exposure in medical workers who perform interventional fluoroscopy procedures. Owing to the nature of certain interventional procedures, workers may be subjected to partial-body radiation exposure that is high enough to cause local damage. We aimed to investigate the level of radiation exposure in interventional radiologists in South Korea by performing cytogenetic biodosimetry, particularly focusing on partial-body exposure. Interventional radiologists (n = 52) completed a questionnaire, providing information about their work history and practices. Blood samples were collected and processed for a dicentric chromosome assay. We determined Papworth's U-value to assess the conformity of dicentrics with the Poisson distribution to estimate the partial-body exposures of the radiologists. Radiologists had a higher number of dicentrics than the normal population and industrial radiographers. Indeed, subjects with a U-value of > 1.96, an indicator of heterogeneous exposure, were observed more frequently; 4.67 ± 0.81% of their body was irradiated at an average dose of 4.64 ± 0.67 Gy. Logistic regression analysis revealed that the total duration of all interventional procedures per week was associated with partial-body exposure levels. Our findings suggest that interventional radiologists had greater chromosomal damages than those in other occupational groups, and their partial-body exposure levels might be high enough to cause local damage. Use of special dosimeters to monitor partial-body exposure, as well as restricting the time and frequency of interventional procedures, could help reduce occupational radiation exposure. • Interventional radiologists had a higher number of dicentrics than the normal population and industrial radiographers. • The level of partial-body exposure of interventional radiologists might be high enough to cause occupational local damage such as a skin cancer in fingers. • Restricting the duration and frequency of interventional procedures might be helpful in reducing occupational radiation exposure.

Cytogenetic follow-up of an individual after accidental exposure to industrial radiation using dicentric frequency in blood lymphocytes

A radiation accident occurred in Bursa, Turkey, in July 2005. An industrial radiographer was exposed to industrial iridium-192 gamma rays for 5 h while laying the natural gas line. After 5 h, the victim had a break because of vomiting and nausea. He ended his work, considering that he might have been exposed to radiation.In a few days, erythema, pain, desquamation, edema started in both hands of the victim. The biological dose assessment was started based on frequencies of dicentrics and rings in peripheral blood lymphocytes ten days after the radiation accident. 6 repeated blood samples were taken for 9 years and analyzed staining after giemsa. After 9 years, decline at dicentric frequencies is significant, but still, dicentric contain cells were detected, which were a strong indicator for external radiation exposure.

The impact of radiation protection training on the radiological safety and the related culture of exposed workers in Greece

The safe use of radiation sources presupposes the engagement of personnel adequately educated and trained on radiation protection and with the necessary safety culture. This is necessary in order to understand their responsibilities and perform their duties in the safest way for themselves, the public and the patients, where appropriate. The Greek Atomic Energy Commission (EEAE) provides education and training on radiation protection to scientists, technical personnel and members of emergency response teams as well as the recognition of the related programs. To fulfil its role, EEAE implements a strategy on education and training in radiation protection through the development of appropriate programs which take into account the national needs, as well as the national capabilities and resources. In this respect, 65 one and two day training seminars were organised in the period 2011–2017 which were attended by 3126 radiation workers (i.e. medical radiology and nuclear medicine technologists, industrial radiographers and outside workers). The present work demonstrates a quantified assessment of the impact of EEAE training activities on particular categories of radiation workers. The study indicates a reduction in Hp(10) values as well as in the corresponding standard deviations of medical radiology technologists, nuclear medicine technologists, and industrial radiographers. A 48% decrease was also observed in the collective dose of medical radiology technologists with cumulative Hp(10) values higher than the investigation level. Moreover, an important improvement of specific safety culture indicators, such as the percentage of non-returned personal dosemeters was noticed and presented.

Assessment of working environment and personal dosimeter-wearing compliance of industrial radiographers based on chromosome aberration frequencies

Industrial radiographers are exposed to relatively higher doses of radiation than other radiation-exposed workers in South Korea. The objective of our study was to investigate the impact of specific occupational conditions on chromosome aberration frequency and evaluate dosimeter-wearing compliance of industrial radiographers in Korea. We studied individual and occupational characteristics of 120 industrial radiographers working in South Korea and evaluated the frequency of dicentrics and translocations in chromosomes to estimate radiation exposure. The association between working conditions and chromosome aberration frequencies was assessed by Poisson regression analysis after adjusting for confounding factors. Legal personal dosimeter-wearing compliance among workers was investigated by correlation analysis between recorded dose and chromosome aberration frequency. Daily average number of radiographic films used in the last six months was associated with dicentrics frequency. Workers performing site radiography showed significantly higher translocation frequency than those working predominantly in shielded enclosures. The correlation between chromosome aberration frequency and recorded dose was higher in workers in the radiography occupation since 2012 (new workers) than other veteran workers. Our study found that site radiography could affect actual radiation exposure to workers. Controlling these working conditions and making an effort to improve personal dosimeter-wearing compliance among veteran workers as well as new workers may be necessary to reduce radiation exposure as much as possible in their workplace.

Mesothelioma mortality within two radiation monitored occupational cohorts

Purpose The risk of mesothelioma, including cancers of the pleura and peritoneum, was examined within two large cohorts of workers monitored for exposure to ionizing radiation. Methods and materials Mortality was assessed among 253,632 workers routinely monitored for external radiation, including 30,724 industrial radiographers (IR) at shipyards, 142,583 workers at nuclear power plants (NPP), and 83,441 IR who had not worked at an NPP or shipyard. Follow-up was from 1969 through 2011. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were computed; observed numbers of deaths from mesothelioma (including cancers of the pleura and peritoneum) and asbestosis were compared with numbers expected based on age-, sex-, and calendar year-specific national mortality rates. Job history and quantitative asbestos exposure data were unavailable, but work at a shipyard was taken as a surrogate for the likelihood of exposure. Cox proportional hazards models were used to estimate hazard ratios (HRs) for mesothelioma in relation to estimated cumulative radiation exposure to the lung. Results The mean duration of follow-up was 25.3 years (max 42 years). The mean cumulative lung dose was 28.6 mGy (7.3% > 250 mGy). Nearly 20% of the workers had died by 2011. A total of 421 mesothelioma deaths were found (75% occurring after 1999) with increased SMRs among workers monitored in shipyards (SMR 9.97; 95% CI 8.50–11.63) and for NPP workers (SMR 5.55; 95% CI 4.88–6.29), but not for IR who had not worked in shipyards (SMR 1.15; 95% CI 0.53–2.19). Likewise, deaths from asbestosis (n = 189) were also increased for shipyard and NPP workers (SMR = 18.1 and 9.2, respectively), but not among workers who never worked at a shipyard or NPP (SMR = 0.70; n = 1). Radiation dose to the lung was not associated with a statistically meaningful dose-response trend for mesothelioma in the combined cohorts (HR at 100 mGy = 1.10; 95% CI 0.96–1.27; p = .18), nor was mesothelioma risk associated with radiation exposure among IR who had not worked in a shipyard and assumed minimally exposed to asbestos. Conclusions An elevated rate of death from mesothelioma was observed in two radiation-exposed occupational groups with potential for asbestos exposure. The increased risk of death from asbestosis, combined with little evidence of a rising trend in mesothelioma mortality with increasing radiation exposure, suggests that the mesothelioma (and asbestosis) excess in these workers was due to asbestos exposure in shipyards and power plants and not to occupational low-dose radiation.

Cytogenetic effects of radiation and genetic polymorphisms of the XRCC1 and XRCC3 repair genes in industrial radiographers.

Different types of DNA damages caused by ionizing radiation may enhance the cancer risk in exposed individuals. Inherited variations in DNA repair genes cause the inter-individual variability in response to ionizing radiation. The purpose of this study was to determine the association between single nucleotide polymorphism (SNP) of two important DNA repair genes (XRCC1 R399Q and XRCC3 T241M) and the level of DNA damage investigated by micronucleus (MN) frequency in peripheral blood lymphocytes of 120 industrial radiographers (IR) and 120 non-exposed control individuals. The frequencies of MN and nucleoplasmic bridges were significantly higher in the IR group than in the control group (33.83 ± 11.96 vs. 7.47 ± 2.96, p < 0.0001 and 1.69 ± 1.86 vs. 0.12 ± 0.33, p < 0.0001). MN frequencies in the IR group were associated with the cumulative radiation doses (p < 0.0001, r = 0.58 for last 1year of exposure and p < 0.0001, r = 0.67 for last 5years of exposure). Polymorphism of XRCC3 T241M was associated with higher MN frequencies in the IR group. However, the same result was not observed between XRCC3 SNP and MN frequency in the control group. Consequently, XRCC3 241Met alleles may cause the increased DNA damage in the industrial radiographers.

Sex-specific lung cancer risk among radiation workers in the million-person study and patients TB-Fluoroscopy

Background The study of Japanese atomic bomb survivors, exposed briefly to radiation, finds the risk of radiation-induced lung cancer to be nearly three times greater for women than for men. Because protection standards for astronauts are based on individual lifetime risk projections, this sex-specific difference limits the time women can spend in space. Populations exposed to chronic or fractionated radiation were evaluated to learn whether similar differences exist when exposures occur gradually over years. Methods and materials Five occupational cohorts within the Million Person Study of Low-Dose Health Effects (MPS) and a Canadian Fluoroscopy Cohort Study (CFCS) of tuberculosis patients who underwent frequent chest fluoroscopic examinations are evaluated. Included are male and female workers at the Mound nuclear facility, nuclear power plants (NPP), and industrial radiographers (IR). Workers at the Mallinckrodt Chemical Works and military participants at aboveground nuclear weapons tests provide information on the risk among males. Cox proportional hazards and Poisson regression models were used to estimate sex-specific radiation risks for lung cancer and to compare any differences. Results Overall, 15,065 lung cancers occurred among the 443,684 subjects studied: 50,111 women and 395,573 men. The mean cumulative dose to the lung was 166.3 mGy (range 6 to 1,055 mGy) with the highest among the TB-fluoroscopy patients (mean 1,055 mGy). Mean lung dose for women in the worker cohorts was generally 4 times lower than for men. Of the 12 estimates of radiation-related risk, only one, for male IRs, showed a significant elevation (ERR 0.09; 95% CI 0.02–0.16, at 100 mGy). In contrast, the dose response for male NPP workers was negative (ERR −0.05; 95% CI −0.10, 0.01, at 100 mGy). Combined, these two cohorts provided little evidence for a radiation effect among males (ERR 0.01; 95% CI −0.04, 0.06, at 100 mGy). There was no significant dose-response among females within any cohort. There was no difference in the sex-specific estimates of lung cancer risk. Conclusions There was little evidence that chronic or fractionated exposures increased the risk of lung cancer. There were no differences in the risks of lung cancer between men and women. However, the sex-specific analyses are limited because of small numbers of women and relatively low doses. A more definitive study is ongoing of medical radiation workers which include 85,000 women and 85,000 men (overall mean dose 82 mGy, max 1,140 mGy). Additional understanding will come from the ongoing follow-up of the CFCS.

Obtaining vital status and cause of death on a million persons

Purpose To present the methodology used to determine vital status and obtain cause of death (COD) within the Million Person Study of Low-Dose Health Effects (MPS). Data sources and vital status tracing techniques used to obtain vital status and COD for six (n = 424,238 subjects) of the ∼20+ cohorts under study are described. Methods and materials A multistage approach using multiple sources of vital status information was used to determine vital status (or ‘trace’) study participants from as early as 1940 to the present. Mortality records from state departments of vital statistics and the Social Security Administration Death Master File (SSA-DMF) were matched to study participants by Social Security Number (SSN), full name, date of birth (DOB), and/or sex using deterministic and probabilistic algorithms. The National Death Index (NDI) and SSA Service for Epidemiological Researchers (SSA-SER) were used to obtain COD (after 1978) and verification of alive status, respectively. Online public records and ancestry services, death certificates, and specialized mortality sources were also utilized. Results For the MPS cohorts traced to date (nuclear power plant workers, industrial radiographers, atomic veterans, and workers at Rocketdyne/Atomics International, Mound nuclear facility, and Mallinckrodt Chemical Works), vital status was confirmed for over 90% of all study subjects in all but one cohort (88%). The ascertainment of COD was over 96% for all cohorts. Conclusions A hallmark of a high-quality epidemiologic cohort mortality study is a low percentage of subjects with unknown vital status and a low percentage of deaths without a COD. The sources and methods used for vital status tracing and COD determination for the MPS have been successful and should be useful for other investigators tracing large, historic study populations. Some of the approaches would be applicable for use in all cohort studies using regional-specific mortality data or modifications to the approach.

LINE-1 hypomethylation is associated with radiation-induced genomic instability in industrial radiographers.

Global DNA hypomethylation is proposed as a potential biomarker for cancer risk associated with genomic instability, which is an important factor in radiation-induced cancer. However, the associations among radiation exposure, changes in DNA methylation, and carcinogenesis are unclear. The aims of this study were (1) to examine whether low-level occupational radiation exposure induces genomic DNA hypomethylation; and (2) to determine the relationships between radiation exposure, genomic DNA hypomethylation and radiation-induced genomic instability (RIGI) in industrial radiographers. Genomic DNA methylation levels were measured in blood DNA from 40 radiographers and 28 controls using the LINE-1 pyrosequencing assay and the luminometric methylation assay. Further, the micronucleus-centromere assay was performed to measure aneuploidy of chromosomes 1 and 4 as a marker of delayed RIGI. Genomic DNA methylation levels were significantly lower in radiographers than those in controls. LINE-1 hypomethylation was not significantly correlated with recent 1-year, recent 3-year, or total cumulative radiation doses in radiographers; however, LINE-1 hypomethylation significantly correlated with the cumulative radiation dose without recent 3-year exposure data (D3dose, r = -0.39, P < 0.05). In addition, LINE-1 hypomethylation was a significant contributor to aneuploidy frequency by D3dose (F (2, 34) = 13.85, P < 0.001), in which a total of 45% of the variance in aneuploidy frequency was explained. Our results provide suggestive evidence regarding the delayed effects of low-dose occupational radiation exposure in radiographers and its association with LINE-1 hypomethylation; however, additional studies using more subjects are needed to fully understand the relationship between genomic DNA hypomethylation and RIGI. Environ. Mol. Mutagen. 60: 174-184, 2019. © 2018 Wiley Periodicals, Inc.

The Past Informs the Future: An Overview of the Million Worker Study and the Mallinckrodt Chemical Works Cohort.

The purpose of this paper is to present an overview of ongoing work on the Million Worker Study (MWS), highlighting some of the key methods and progress so far as exemplified by the study of workers at the Mallinckrodt Chemical Works (MCW). The MWS began nearly 25 y ago and continues in a stepwise fashion, evaluating one study cohort at a time. It includes workers from U.S. Department of Energy (DOE) Manhattan Project facilities, U.S. Nuclear Regulatory Commission (NRC) regulated nuclear power plants, industrial radiographers, U.S. Department of Defense (DoD) nuclear weapons test participants, and physicians and technologists working with medical radiation. The purpose is to fill the major gap in radiation protection and science: What is the risk when exposure is received gradually over time rather than briefly as for the atomic bomb survivors? Studies published or planned in 2018 include leukemia (and dosimetry) among atomic veterans, leukemia among nuclear power plant workers, mortality among workers at the MCW, and a comprehensive National Council on Radiation Protection and Measurements (NCRP) Report on dosimetry for the MWS. MCW has a singular place in history: the 40 tons (T) of uranium oxide produced at MCW were used by Enrico Fermi on 2 December 1942 to produce the first manmade sustained and controlled nuclear reaction, and the atomic age was born. Seventy-six years later, the authors followed the over 2,500 MCW workers for mortality and reconstructed dose from six sources of exposure: external gamma rays from the radioactive elements in pitchblende; medical x rays from occupationally required chest examinations; intakes of pitchblende (uranium, radium, and silica) measured by urine samples; radon breath analyses and dust surveys overseen by Robley Evans and Merril Eisenbud; occupational exposures received before and after employment at MCW; and cumulative radon concentrations and lung dose from the decay of radium in the work environment. The unique exposure reconstructions allow for multiple evaluations, including estimates of silica dust. The study results are relevant today. For example, NASA is interested that radium, deposited in the brain, releases high-LET alpha particles - the only human analogue, though limited, for high energy, high-Z particles (galactic cosmic rays) traveling through space that might affect astronauts on Mars missions. Don't discount the past; it's the prologue to the future!

Assessing the health effects associated with occupational radiation exposure in Korean radiation workers: protocol for a prospective cohort study

IntroductionThe cancer risk of radiation exposure in the moderate-to-high dose range has been well established. However, the risk remains unclear at low-dose ranges with protracted low-dose rate exposure, which is...

DOSIMETRIC ASPECTS OF OPTIMIZATION OF PROTECTION IN IRAN INDUSTRIAL RADIOGRAPHY PRACTICE.

According to the worldwide reports, industrial radiography is one of the highest risk radiation practices due to handling high activity sources. Therefore, an optimization of protection along with appropriate investigation level and/or dose constraint is required to achieve appropriate radiological safety. This research, presents some statistical aspects of this optimization using frequency distributions and percentiles of individual recorded dose of industrial radiographers from the years 2002 to 2016 in Iran. The results show that, considering an investigation level of 4 mSv for bimonthly monitoring periods, 3-7% of population of workers has been investigated during these years. Moreover, an overall reduction on average annual and collective doses is observed, despite of the relative increasing in the number of workers. Since the frequency of periodical recorded dose at lower dose range (e.g. <4 mSv) causes greater impacts on the reduction of collective dose than the higher ranges, a retrospective average dose of non-investigated workers can also be substitute with a constant value as a dose constraint. It can be concluded that all the past measures of regulatory body and attempts of the employers have been effective improving the radiological protection in this practice in Iran. However, establishing a dose constraint seems to be essential to continue and improve this optimization of protection.

The Effect of Protracted Exposure to Radiation on Liver Injury: A Cohort Study of Industrial Radiographers in Xinjiang, China.

Background: At present, a large number of studies indicate that high dose ionizing radiation exposure is an important risk factor for liver damage. Whether protracted exposure to low external doses of ionizing radiation could induce liver injury is unclear. The aim of this study was to assess the risk of liver injury following protracted exposure to occupational radiation compared to a group of unexposed workers. Methods: A three-year cohort study was initiated in Xinjiang, China in 2010 and included 508 industrial radiographers and 2156 unexposed workers. The incidence of liver injury was assessed clinically based on the evaluation of alanine aminotransferase (ALT) and aspartate transaminase (AST) levels. Logistic regression was used to examine whether radiation is a risk factor for liver injury. Results: Compared with the unexposed group, protracted radiation exposure was found to be a risk factor for liver injury. Sex, age at baseline and alcohol consumption were not associated with liver injury. However, hypertension was a risk factor for liver injury. The association between cumulative recorded radiation dose and liver injury was not found in this study. Conclusions: These findings indicate that protracted exposure to radiation is a risk factor for liver injury.

Buccal mucosa micronuclei counts in relation to exposure to low dose-rate radiation from the Chornobyl nuclear accident and other medical and occupational radiation exposures

BackgroundIonizing radiation is a well-known carcinogen. Chromosome aberrations, and in particular micronuclei represent an early biological predictor of cancer risk. There are well-documented associations of micronuclei with ionizing radiation dose in some radiation-exposed groups, although not all. That associations are not seen in all radiation-exposed groups may be because cells with micronuclei will not generally pass through mitosis, so that radiation-induced micronuclei decay, generally within a few years after exposure.MethodsBuccal samples from a group of 111 male workers in Ukraine exposed to ionizing radiation during the cleanup activities at the Chornobyl nuclear power plant were studied. Samples were taken between 12 and 18 years after their last radiation exposure from the Chornobyl cleanup. The frequency of binucleated micronuclei was analyzed in relation to estimated bone marrow dose from the cleanup activities along with a number of environmental/occupational risk factors using Poisson regression adjusted for overdispersion.ResultsAmong the 105 persons without a previous cancer diagnosis, the mean Chornobyl-related dose was 59.5 mSv (range 0–748.4 mSv). There was a borderline significant increase in micronuclei frequency among those reporting work as an industrial radiographer compared with all others, with a relative risk of 6.19 (95% CI 0.90, 31.08, 2-sided p = 0.0729), although this was based on a single person. There was a borderline significant positive radiation dose response for micronuclei frequency with increase in micronuclei per 1000 scored cells per Gy of 3.03 (95% CI -0.78, 7.65, 2-sided p = 0.1170), and a borderline significant reduction of excess relative MN prevalence with increasing time since last exposure (p = 0.0949). There was a significant (p = 0.0388) reduction in MN prevalence associated with bone X-ray exposure, but no significant trend (p = 0.3845) of MN prevalence with numbers of bone X-ray procedures.ConclusionsThere are indications of increasing trends of micronuclei prevalence with Chornobyl-cleanup-associated dose, and indications of reduction in radiation-associated excess prevalence of micronuclei with time after exposure. There are also indications of substantially increased micronuclei associated with work as an industrial radiographer. This analysis adds to the understanding of the long-term effects of low-dose radiation exposures on relevant cellular structures and methods appropriate for long-term radiation biodosimetry.