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Sleiman A, Miller KB, Flores D, Kuan J, Altwasser K, Smith BJ, Kozbenko T, Hocking R, Wood SJ, Huff J, Adam-Guillermin C, Hamada N, Yauk C, Wilkins R, Chauhan V. AOP report: Development of an adverse outcome pathway for deposition of energy leading to learning and memory impairment. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024. [PMID: 39228295 DOI: 10.1002/em.22622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2024] [Accepted: 08/14/2024] [Indexed: 09/05/2024]
Abstract
Understanding radiation-induced non-cancer effects on the central nervous system (CNS) is essential for the risk assessment of medical (e.g., radiotherapy) and occupational (e.g., nuclear workers and astronauts) exposures. Herein, the adverse outcome pathway (AOP) approach was used to consolidate relevant studies in the area of cognitive decline for identification of research gaps, countermeasure development, and for eventual use in risk assessments. AOPs are an analytical construct describing critical events to an adverse outcome (AO) in a simplified form beginning with a molecular initiating event (MIE). An AOP was constructed utilizing mechanistic information to build empirical support for the key event relationships (KERs) between the MIE of deposition of energy to the AO of learning and memory impairment through multiple key events (KEs). The evidence for the AOP was acquired through a documented scoping review of the literature. In this AOP, the MIE is connected to the AO via six KEs: increased oxidative stress, increased deoxyribonucleic acid (DNA) strand breaks, altered stress response signaling, tissue resident cell activation, increased pro-inflammatory mediators, and abnormal neural remodeling that encompasses atypical structural and functional alterations of neural cells and surrounding environment. Deposition of energy directly leads to oxidative stress, increased DNA strand breaks, an increase of pro-inflammatory mediators and tissue resident cell activation. These KEs, which are themselves interconnected, can lead to abnormal neural remodeling impacting learning and memory processes. Identified knowledge gaps include improving quantitative understanding of the AOP across several KERs and additional testing of proposed modulating factors through experimental work. Broadly, it is envisioned that the outcome of these efforts could be extended to other cognitive disorders and complement ongoing work by international radiation governing bodies in their review of the system of radiological protection.
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Affiliation(s)
- Ahmad Sleiman
- Institut de Radioprotection et de Sûreté Nucléaire, St. Paul Lez Durance, Provence, France
| | - Kathleen B Miller
- Department of Health and Exercise Science, Morrison College Family of Health, University of St. Thomas, Saint Paul, Minnesota, USA
| | - Danicia Flores
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Jaqueline Kuan
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Kaitlyn Altwasser
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Benjamin J Smith
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Tatiana Kozbenko
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Robyn Hocking
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | | | - Janice Huff
- NASA Langley Research Center, Hampton, Virginia, USA
| | | | - Nobuyuki Hamada
- Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Chiba, Japan
| | - Carole Yauk
- Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
| | - Ruth Wilkins
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
| | - Vinita Chauhan
- Consumer and Clinical Radiation Protection Bureau, Environmental and Radiation Health Sciences Directorate, Health Canada, Ottawa, Ontario, Canada
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Little MP, Bazyka D, de Gonzalez AB, Brenner AV, Chumak VV, Cullings HM, Daniels RD, French B, Grant E, Hamada N, Hauptmann M, Kendall GM, Laurier D, Lee C, Lee WJ, Linet MS, Mabuchi K, Morton LM, Muirhead CR, Preston DL, Rajaraman P, Richardson DB, Sakata R, Samet JM, Simon SL, Sugiyama H, Wakeford R, Zablotska LB. A Historical Survey of Key Epidemiological Studies of Ionizing Radiation Exposure. Radiat Res 2024; 202:432-487. [PMID: 39021204 PMCID: PMC11316622 DOI: 10.1667/rade-24-00021.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 04/23/2024] [Indexed: 07/20/2024]
Abstract
In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis.
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Affiliation(s)
- Mark P. Little
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
- Faculty of Health and Life Sciences, Oxford Brookes University, Headington Campus, Oxford, OX3 0BP, UK
| | - Dimitry Bazyka
- National Research Center for Radiation Medicine, Hematology and Oncology, 53 Melnikov Street, Kyiv 04050, Ukraine
| | | | - Alina V. Brenner
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Vadim V. Chumak
- National Research Center for Radiation Medicine, Hematology and Oncology, 53 Melnikov Street, Kyiv 04050, Ukraine
| | - Harry M. Cullings
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Robert D. Daniels
- National Institute for Occupational Safety and Health, Cincinnati, OH, USA
| | - Benjamin French
- Department of Biostatistics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Eric Grant
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Nobuyuki Hamada
- Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan
| | - Michael Hauptmann
- Institute of Biostatistics and Registry Research, Brandenburg Medical School Theodor Fontane, 16816 Neuruppin, Germany
| | - Gerald M. Kendall
- Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Richard Doll Building, Old Road Campus, Headington, Oxford, OX3 7LF, UK
| | - Dominique Laurier
- Institute for Radiological Protection and Nuclear Safety, Fontenay aux Roses France
| | - Choonsik Lee
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
| | - Won Jin Lee
- Department of Preventive Medicine, Korea University College of Medicine, Seoul, South Korea
| | - Martha S. Linet
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
| | - Kiyohiko Mabuchi
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
| | - Lindsay M. Morton
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
| | | | | | - Preetha Rajaraman
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - David B. Richardson
- Environmental and Occupational Health, 653 East Peltason, University California, Irvine, Irvine, CA 92697-3957 USA
| | - Ritsu Sakata
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Jonathan M. Samet
- Department of Epidemiology, Colorado School of Public Health, Aurora, Colorado, USA
| | - Steven L. Simon
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892-9778, USA
| | - Hiromi Sugiyama
- Radiation Effects Research Foundation, 5-2 Hijiyama Park, Minami-ku, Hiroshima 732-0815, Japan
| | - Richard Wakeford
- Centre for Occupational and Environmental Health, The University of Manchester, Ellen Wilkinson Building, Oxford Road, Manchester, M13 9PL, UK
| | - Lydia B. Zablotska
- Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco, 550 16 Street, 2 floor, San Francisco, CA 94143, USA
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Pszczołowska M, Walczak K, Miśków W, Mroziak M, Kozłowski G, Beszłej JA, Leszek J. Association between Female Reproductive Factors and Risk of Dementia. J Clin Med 2024; 13:2983. [PMID: 38792524 PMCID: PMC11122498 DOI: 10.3390/jcm13102983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/07/2024] [Accepted: 05/16/2024] [Indexed: 05/26/2024] Open
Abstract
Women have an over 50% greater risk of dementia than men, which is a main topic of much research. This review aims to investigate the impact of a woman's reproductive history on dementia risk. The consequences of stillbirth are long-term health and psychosocial problems for women. Because of the awareness of an endangered pregnancy, many parents experience deep anxiety and stress in subsequent pregnancies. There are contradictory conclusions from research about abortion and the risk of dementia correlation. When it comes to the late age of first birth, which is said to be above 35 years old, it was observed that older mothers have a decreased risk of dementia compared to those who gave birth in their 20s; however, being a child of the older mother is connected with a higher risk of developing dementia. Using hormonal contraception can result in decreased risk of dementia as estrogen stimulates microglia-related Aβ removal and reduces tau hyperphosphorylation. The influence of postmenopausal hormonal therapy and the duration of the reproductive period on developing dementia remains unclear. Although female disorders like endometriosis and polycystic ovary syndrome are reported to increase the risk of dementia, the research on this topic is very limited, especially when it comes to endometriosis, and needs further investigation. Interestingly, there is no conclusion on whether hypertensive disorders of pregnancy increase the risk of dementia, but most articles seem to confirm this theory.
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Affiliation(s)
| | - Kamil Walczak
- Faculty of Medicine, Wrocław Medical University, 50-367 Wrocław, Poland
| | - Weronika Miśków
- Faculty of Medicine, Wrocław Medical University, 50-367 Wrocław, Poland
| | - Magdalena Mroziak
- Faculty of Medicine, Wrocław Medical University, 50-367 Wrocław, Poland
| | - Gracjan Kozłowski
- Faculty of Medicine, Wrocław Medical University, 50-367 Wrocław, Poland
| | - Jan Aleksander Beszłej
- Clinic of Psychiatry, Department of Psychiatry, Medical Department, Wrocław Medical University, 50-367 Wrocław, Poland
| | - Jerzy Leszek
- Clinic of Psychiatry, Department of Psychiatry, Medical Department, Wrocław Medical University, 50-367 Wrocław, Poland
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Dauer LT, Walsh L, Mumma MT, Cohen SS, Golden AP, Howard SC, Roemer GE, Boice JD. 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. Z Med Phys 2024; 34:100-110. [PMID: 37537100 PMCID: PMC10919963 DOI: 10.1016/j.zemedi.2023.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 07/06/2023] [Accepted: 07/07/2023] [Indexed: 08/05/2023]
Abstract
BACKGROUND Radiation 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 METHODS The 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. RESULTS The 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). CONCLUSIONS Parkinson'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.
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Affiliation(s)
- Lawrence T Dauer
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
| | - Linda Walsh
- Department of Physics, University of Zürich, Zürich, Switzerland
| | - Michael T Mumma
- Vanderbilt University Medical Center's International Epidemiology Field Station, Rockville, MD, USA
| | | | - Ashley P Golden
- ORISE Health Studies Program, Oak Ridge Associated Universities, Oak Ridge, TN, USA
| | - Sara C Howard
- ORISE Health Studies Program, Oak Ridge Associated Universities, Oak Ridge, TN, USA
| | - Grace E Roemer
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - John D Boice
- National Council on Radiation Protection and Measurements, Bethesda, MD, USA; Vanderbilt University School of Medicine, Nashville, TN, USA
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Milder CM, Howard SC, Ellis ED, Golden AP, Cohen SS, Mumma MT, Leggett RW, French B, Zablotska LB, Boice JD. Third mortality follow-up of the Mallinckrodt uranium processing workers, 1942-2019. Int J Radiat Biol 2024; 100:161-175. [PMID: 37819879 PMCID: PMC10843089 DOI: 10.1080/09553002.2023.2267640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 09/28/2023] [Indexed: 10/13/2023]
Abstract
INTRODUCTION Mallinckrodt Chemical Works was a uranium processing facility during the Manhattan Project from 1942 to 1966. Thousands of workers were exposed to low-dose-rates of ionizing radiation from external and internal sources. This third follow-up of 2514 White male employees updates cancer and noncancer mortality potentially associated with radiation and silica dust. MATERIALS AND METHODS Individual, annualized organ doses were estimated from film badge records (n monitored = 2514), occupational chest x-rays (n = 2514), uranium urinalysis (n = 1868), radium intake through radon breath measurements (n = 487), and radon ambient measurements (n = 1356). Silica dust exposure from pitchblende processing was estimated (n = 1317). Vital status and cause of death determination through 2019 relied upon the National Death Index and Social Security Administration Epidemiological Vital Status Service. The analysis included standardized mortality ratios (SMRs), Cox proportional hazards, and Poisson regression models. RESULTS Vital status was confirmed for 99.4% of workers (84.0% deceased). For a dose weighting factor of 1 for intakes of uranium, radium, and radon decay products, the mean and median lung doses were 65.6 and 29.9 mGy, respectively. SMRs indicated a difference in health outcomes between salaried and hourly workers, and more brain cancer deaths than expected [SMR: 1.79; 95% confidence interval (CI): 1.14, 2.70]. No association was seen between radiation and lung cancer [hazard ratio (HR) at 100 mGy: 0.93; 95%CI: 0.78, 1.11]. The relationship between radiation and kidney cancer observed in the previous follow-up was maintained (HR at 100 mGy: 2.07; 95%CI: 1.12, 3.79). Cardiovascular disease (CVD) also increased significantly with heart dose (HR at 100 mGy: 1.11; 95%CI: 1.02, 1.21). Exposures to dust ≥23.6 mg/m3-year were associated with nonmalignant kidney disease (NMKD) (HR: 3.02; 95%CI: 1.12, 8.16) and kidney cancer combined with NMKD (HR: 2.46; 95%CI: 1.04, 5.81), though without evidence of a dose-response per 100 mg/m3-year. CONCLUSIONS This third follow-up of Mallinckrodt uranium processors reinforced the results of the previous studies. There was an excess of brain cancers compared with the US population, although no radiation dose-response was detected. The association between radiation and kidney cancer remained, though potentially due to few cases at higher doses. The association between levels of silica dust ≥23.6 mg/m3-year and NMKD also remained. No association was observed between radiation and lung cancer. A positive dose-response was observed between radiation and CVD; however, this association may be confounded by smoking, which was unmeasured. Future work will pool these data with other uranium processing worker cohorts within the Million Person Study.
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Affiliation(s)
- Cato M. Milder
- Division of Epidemiology, Vanderbilt University Medical Center, Nashville, TN, USA
- Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute
| | | | | | | | - Sarah S. Cohen
- EpidStrategies, a Division of ToxStrategies, Inc., Katy, TX
| | | | | | - Benjamin French
- Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Lydia B. Zablotska
- Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco, CA, USA
| | - John D. Boice
- Division of Epidemiology, Vanderbilt University Medical Center, Nashville, TN, USA
- National Council on Radiation Protection and Measurements (NCRP), Bethesda, MD, USA
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Thariat J, Little MP, Zablotska LB, Samson P, O’Banion MK, Leuraud K, Bergom C, Girault G, Azimzadeh O, Bouffler S, Hamada N. Radiotherapy for non-cancer diseases: benefits and long-term risks. Int J Radiat Biol 2024; 100:505-526. [PMID: 38180039 PMCID: PMC11039429 DOI: 10.1080/09553002.2023.2295966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 11/29/2023] [Indexed: 01/06/2024]
Abstract
PURPOSE The discovery of X-rays was followed by a variety of attempts to treat infectious diseases and various other non-cancer diseases with ionizing radiation, in addition to cancer. There has been a recent resurgence of interest in the use of such radiotherapy for non-cancer diseases. Non-cancer diseases for which use of radiotherapy has currently been proposed include refractory ventricular tachycardia, neurodegenerative diseases (e.g. Alzheimer's disease and dementia), and Coronavirus Disease 2019 (COVID-19) pneumonia, all with ongoing clinical studies that deliver radiation doses of 0.5-25 Gy in a single fraction or in multiple daily fractions. In addition to such non-cancer effects, historical indications predominantly used in some countries (e.g. Germany) include osteoarthritis and degenerative diseases of the bones and joints. This narrative review gives an overview of the biological rationale and ongoing preclinical and clinical studies for radiotherapy proposed for various non-cancer diseases, discusses the plausibility of the proposed biological rationale, and considers the long-term radiation risks of cancer and non-cancer diseases. CONCLUSIONS A growing body of evidence has suggested that radiation represents a double-edged sword, not only for cancer, but also for non-cancer diseases. At present, clinical evidence has shown some beneficial effects of radiotherapy for ventricular tachycardia, but there is little or no such evidence of radiotherapy for other newly proposed non-cancer diseases (e.g. Alzheimer's disease, COVID-19 pneumonia). Patients with ventricular tachycardia and COVID-19 pneumonia have thus far been treated with radiotherapy when they are an urgent life threat with no efficient alternative treatment, but some survivors may encounter a paradoxical situation where patients were rescued by radiotherapy but then get harmed by radiotherapy. Further studies are needed to justify the clinical use of radiotherapy for non-cancer diseases, and optimize dose to diseased tissue while minimizing dose to healthy tissue.
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Affiliation(s)
- Juliette Thariat
- Department of Radiation Oncology, Comprehensive Cancer Centre François Baclesse, Caen, France
- Laboratoire de Physique Corpusculaire IN2P3, ENSICAEN/CNRS UMR 6534, Normandie Université, Caen, France
| | - Mark P. Little
- Radiation Epidemiology Branch, National Cancer Institute, Bethesda, Maryland, USA
| | - Lydia B. Zablotska
- Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco (UCSF), San Francisco, California, USA
| | - Pamela Samson
- Department of Radiation Oncology, Alvin J. Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri, USA
| | - M. Kerry O’Banion
- Department of Neuroscience, Del Monte Institute for Neuroscience, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
| | - Klervi Leuraud
- Research Department on Biological and Health Effects of Ionizing Radiation (SESANE), Institute for Radiological Protection and Nuclear Safety (IRSN), Fontenay-aux-Roses, France
| | - Carmen Bergom
- Department of Radiation Oncology, Alvin J. Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri, USA
- Cardio-Oncology Center of Excellence, Washington University, St. Louis, Missouri, USA
| | - Gilles Girault
- Comprehensive Cancer Centre François Baclesse, Medical Library, Caen, France
| | - Omid Azimzadeh
- Federal Office for Radiation Protection (BfS), Section Radiation Biology, Neuherberg, Germany
| | - Simon Bouffler
- Radiation Protection Sciences Division, UK Health Security Agency (UKHSA), Chilton, Didcot, UK
| | - Nobuyuki Hamada
- Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Abiko, Chiba, Japan
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7
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Hamada N. Noncancer Effects of Ionizing Radiation Exposure on the Eye, the Circulatory System and beyond: Developments made since the 2011 ICRP Statement on Tissue Reactions. Radiat Res 2023; 200:188-216. [PMID: 37410098 DOI: 10.1667/rade-23-00030.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 06/13/2023] [Indexed: 07/07/2023]
Abstract
For radiation protection purposes, noncancer effects with a threshold-type dose-response relationship have been classified as tissue reactions (formerly called nonstochastic or deterministic effects), and equivalent dose limits aim to prevent occurrence of such tissue reactions. Accumulating evidence demonstrates increased risks for several late occurring noncancer effects at doses and dose rates much lower than previously considered. In 2011, the International Commission on Radiological Protection (ICRP) issued a statement on tissue reactions to recommend a threshold of 0.5 Gy to the lens of the eye for cataracts and to the heart and brain for diseases of the circulatory system (DCS), independent of dose rate. Literature published thereafter continues to provide updated knowledge. Increased risks for cataracts below 0.5 Gy have been reported in several cohorts (e.g., including in those receiving protracted or chronic exposures). A dose threshold for cataracts is less evident with longer follow-up, with limited evidence available for risk of cataract removal surgery. There is emerging evidence for risk of normal-tension glaucoma and diabetic retinopathy, but the long-held tenet that the lens represents among the most radiosensitive tissues in the eye and in the body seems to remain unchanged. For DCS, increased risks have been reported in various cohorts, but the existence or otherwise of a dose threshold is unclear. The level of risk is less uncertain at lower dose and lower dose rate, with the possibility that risk per unit dose is greater at lower doses and dose rates. Target organs and tissues for DCS are also unknown, but may include heart, large blood vessels and kidneys. Identification of potential factors (e.g., sex, age, lifestyle factors, coexposures, comorbidities, genetics and epigenetics) that may modify radiation risk of cataracts and DCS would be important. Other noncancer effects on the radar include neurological effects (e.g., Parkinson's disease, Alzheimer's disease and dementia) of which elevated risk has increasingly been reported. These late occurring noncancer effects tend to deviate from the definition of tissue reactions, necessitating more scientific developments to reconsider the radiation effect classification system and risk management. This paper gives an overview of historical developments made in ICRP prior to the 2011 statement and an update on relevant developments made since the 2011 ICRP statement.
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Affiliation(s)
- Nobuyuki Hamada
- Biology and Environmental Chemistry Division, Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), Chiba, Japan
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