Low-dose Radiation Exposure Research Articles

LDR-adapted liver-derived cytokines have potential to induce atherosclerosis

Purpose Atherosclerosis is a lipid-driven chronic inflammatory disease that causes cardiovascular diseases (CVD). The association between radiation and atherosclerosis has already been demonstrated; however, the effects of low-dose radiation (LDR) exposure on atherosclerosis have not been reported. Our study aims to propose that LDR may cause atherosclerosis phenotypes by the upregulation of plasminogen activator inhibitor-1 (PAI-1) and downregulation of androgen receptor (AR), which are cytokines secreted from the liver. Methods Low-density lipoprotein (LDL) receptor deficient (Ldlr−/−) mice were irradiated at 50 mGy, 100 mGy, and 1000 mGy. LDR irradiated Ldlr−/− mice serum was analyzed by cytokine array and proteomics with silver staining. Oil Red O staining and BODIPY staining were performed to determine lipid accumulation in Human umbilical vein endothelial cells (HUVECs). Foam cell formation and monocyte recruitment were assessed through co-culture system with HUVECs and THP-1 cells. Results After irradiation with LDR (100 mGy) the mice showed atherosclerotic phenotypes and through analysis results, we selected regulated cytokines, PAI-1 and AR, and found that these were changed in the liver. LDR-regulated cytokines have the potential to be transported to endothelial cells and induce lipid accumulation, inflammation of monocytes, increased oxidized low-density lipoprotein (oxLDL) and foam cells formation, that were series of phenotypes lead to plaque formation in endothelial cells and induces atherosclerosis. As a further aspect of this study, testosterone undecanoate (TU) was found to pharmacologically inhibit a series of atherosclerotic phenotypes exhibited by LDR. This study suggests a role for PAI-1 and AR in regulating the development of atherosclerosis after LDR exposure. Targeting PAI-1 and AR could serve as an attractive strategy for the management of atherosclerosis following LDR exposure.

Biological Effects of Low Dose Radiation (LDR) on Peri-Tumoral and Tumoral Areas with Squamous Cell Skin Cancer

<h3>Purpose/Objective(s)</h3> Low dose radiation (LDR) may have paradoxically beneficial effects via an adaptive response. We aimed to assess the adaptive response of healthy and malignant skin tissue to low doses of radiation and explore the molecular details behind the induced adaptive response. <h3>Materials/Methods</h3> We conducted a prospective, randomized pilot study (N=8) to ascertain the biological effects of integrating 0.1 Gy of LDR into standard radiotherapy sessions (2.0 Gy fractions) over the first two weeks of radiotherapy for patients 18-80 years of age (both sexes) diagnosed with squamous cell carcinoma of skin (lesions of 1 – 10 cm). Radiation treatment was done with a linear accelerator. The patients received definitive radiation for the tumor as determined by the treating physician using 2.0 Gy fractions. In addition, 0.1 Gy of LDR was integrated into the standard radiotherapy course on day 0 and day 6 over the first two weeks of treatment. Radiation delivery to healthy tissue was with a 1.5 cm margin around the tumor using a mask over the tumor. We obtained partial thickness skin biopsy samples of the tumor and peri-tumoral normal tissue before treatment from four patients (for control). An additional four patients (actively treated) were biopsied before and 24 hours after 0.1 Gy of LDR (day 0, 1 and day 6, 7). RNA was obtained from skin biopsies and processed for genetic expression (138K genes). <h3>Results</h3> The change in gene expression in healthy peri-tumoral tissues due to LDR exposure was relatively low (only 325 genes: 170 upregulated, 155 downregulated). The <i>senescence and autophagy in cancer</i> and <i>genotoxicity pathway</i> genes showed the most significant downregulation in peritumoral healthy tissue comparing days 0 and 1. The biological pathways in peritumoral healthy tissue comparing days 6 and 7 showed predominantly downregulation of genes with most pronounced downregulation seen in <i>electron transport chain in mitochondria</i> and genes involved in <i>non-alcoholic fatty liver disease</i>. In contrast to normal peritumoral tissue, the difference in gene expression in tumor tissue due to LDR exposure was significantly more pronounced (5,651 genes: 2,896 upregulated, 2,755 downregulated) The <i>allograft rejection</i> genes and <i>nuclear receptor meta-pathway</i> were the most upregulated in the tumoral tissues comparing days 0 and 1. The nuclear receptor meta-pathway were the most upregulated in the tumoral tissues on days 6 and 7. The <i>Allograft rejection pathway in skin cancer</i> was among those upregulated. <h3>Conclusion</h3> LDR had a modest effect on miRNA expression when applied to healthy peritumoral skin. Downregulated pathways predominate, and DNA repair mechanisms are stimulated by the first dose in healthy tissue. In contrast, a more pronounced effect on gene expression (as measured by miRNA profiles), including upregulation of several key relevant pathways, was induced by LDR to malignant tissue.

Cohort profile: The Australian Paediatric Exposure to Radiation Cohort (Aust-PERC).

Although the carcinogenic effects of high-dose radiation are well-established, the risks at low doses, such as from diagnostic X-rays, are less well understood. Children are susceptible to radiation induced cancers, and in the last decade, several cohort studies have reported increased cancer risks following computed tomography (CT) scans in childhood. However, cohort studies can be limited by insufficient follow-up, indication bias, reverse causation, or by lack of organ doses from CT scans or other exposures. Aust-PERC is a retrospective cohort designed to study the effects of low-dose medical radiation exposure, primarily from CT scans, in young Australians. The cohort was ascertained using deidentified billing records from patients who were aged 0–19 years while enrolled in Medicare (Australia’s universal healthcare system) between 1985 and 2005. All procedures billed to Medicare in this age/time window that involved low-dose radiation were identified, and persons without such procedures were flagged as unexposed. The Aust-PERC cohort has been linked, using confidential personal identifiers, to the Australian Cancer Database and the National Death Index, on two occasions (to Dec. 2007 and Dec. 2012) by the responsible government agency (Australian Institute of Health and Welfare). Deidentified Medicare service records of all radiological procedures including CT scans, nuclear medicine (NM) scans and fluoroscopy and plain X-ray procedures have been available to derive estimated radiation doses in the cohort. Records of other medical and surgical procedures, together with demographic and socioeconomic variables are being used in analyses to assess biases arising from reverse causation and confounding. After excluding patients with errant records, 11 802 846 persons remained in the baseline cohort, with an average follow-up time of 22.3 years to December 2012. There were 275 489 patients exposed to diagnostic nuclear medicine scans and 688 363 patients exposed to CT scans before age 20 and before cancer diagnosis. Between 1 January 1985 and 31 December 2012, there were 105 124 deaths and 103 505 incident cancers. Dose-response analyses based on the relevant organ doses are underway for individual cancers, and we plan to extend the follow-up for another 8 years to Dec 2020. Analyses using this very large Aust-PERC cohort, with extended follow-up, will help to resolve international uncertainties about the causal role of diagnostic medical radiation as a cause of cancer.

BIOLOGICAL EFFECTS OF LOW-DOSE RADIATION FROM CT IMAGING.

The dramatic rise in diagnostic procedures, radioisotope-based scans and intervention procedures has created a very valid concern regarding the long-term biological consequences from exposure to low doses of ionizing radiation. Despite its unambiguous medical benefits, additional knowledge on the health outcome of its use is essential. This review summarizes the available information regarding the biological consequences of low-dose radiation (LDR) exposure in humans (e.g. cytogenetic changes, cancer risk and radiation-induced cataracts. However, LDR studies remain relatively new and thus an encompassing view of its biological effects and relevant mechanisms in the human body is still needed.

Evaluation of natural chronic low dose radiation exposure on telomere length and transcriptional response of shelterin complex in individuals residing in Kerala coast, India

The high level natural radiation areas (HLNRA) of Kerala coast provide unique opportunity to study the biological effect of chronic low dose ionizing radiation (LDIR) on human population below 100 mSv. The radiation level in this area varies from < 1.0–45 mGy /year due to patchy distribution of monazite in the sand, which contains 232Th (8–10%), 238U (0.3%), and their decay products. Telomere length attrition has been correlated to DNA damage due to genotoxic agents. The objective of the present study is to evaluate the effect of natural chronic LDIR exposure on telomere length and transcriptional response of telomere specific and DNA damage repair genes in peripheral blood mononuclear cells (PBMCs) of individuals from normal level natural radiation areas (NLNRA) and HLNRA of Kerala coast, southwest India. Blood samples were collected from 71 random male donors (24–80 years) from NLNRA (≤1.50 mGy/year; N = 19) and two HLNRA dose groups [1.51–10 mGy/year (N = 17); > 10 mGy/year, (N = 35)]. Genomic DNA was isolated from PBMCs and relative telomere length (RTL) was determined using real time q-PCR. Radio-adaptive response (RAR) study was carried out in PBMCs of 40 random males from NLNRA (N = 20) and HLNRA (>10 mGy/year; N = 20), where PBMCs were given a challenged dose of 2.0 Gy gamma radiation at 4 h. Transcriptional profile of telomere specific (TRF1, TRF2, POT1, TIN2, TPP1, RAP1), DNA damage response (RAD17, ATM, CHEK1) and base excision repair pathway (BER) (OGG1, XRCC1, NTH1, NEIL1, MUTYH, MBD4) genes were analysed at basal level and after a challenge dose of 2.0 Gy at 4 h. Our results did not show any significant effect of chronic LDR on RTL among the individuals from NLNRA and two HLNRA groups (p = 0.195). However, influence of age on RTL was clearly evident among NLNRA and HLNRA individuals. At basal level, TRF1, TRF2, TIN2, MBD4, NEIL1 and RAD17 showed significant up-regulation, whereas XRCC1 was significantly down regulated in HLNRA individuals. After a challenge dose of 2.0 Gy, significant transcriptional up-regulation was observed at telomere specific (TRF2, POT1) and BER (MBD4, NEIL1) genes in HLNRA individuals as compared to NLNRA suggesting their role in RAR. In conclusion, elevated level of natural chronic LDR exposure did not have any adverse effect on telomere length in Kerala coast. Significant transcriptional response at TRF2, MBD4 and NEIL1 at basal level and with a challenge dose of 2.0 Gy suggested their active involvement in efficient repair and telomere maintenance in individuals from HLNRA of Kerala coast.

Occupational Low-Dose Radiation Affects the Expression of Immune Checkpoint of Medical Radiologists.

The purpose of this study was to investigate the expression of immune checkpoint cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and T cell immunoglobulin and mucin domain 3 (TIM-3) in the peripheral blood T lymphocytes of medical radiologists. The study incorporated 100 male medical radiologists and 107 male healthy controls. The expressions of CTLA-4 and TIM-3 among CD4+ and CD8+ lymphocytes were detected by flow cytometry. The expression levels of CTLA-4 and TIM-3 in the CD4+T cells of radiation workers were lower than those of healthy controls (p < 0.05). Correlation analysis showed that the CD8+CTLA-4 expression level was significantly positively correlated with individual cumulative dose (rs = 0.260, p = 0.001, <0.05), while the expression level of CD8+TIM-3 was negatively correlated (rs = −0.180, p = 0.027, <0.05). Low-dose radiation exposure affects the expression of CTLA-4 and TIM-3 in human peripheral blood T lymphocytes. Future studies need to focus on exploring the mechanisms by which CTLA-4 and TIM-3 expression changes in response to low-dose radiation exposure.

Complex housing partially mitigates low dose radiation-induced changes in brain and behavior in rats

In recent years, much effort has been focused on developing new strategies for the prevention and mitigation of adverse radiation effects on healthy tissues and organs, including the brain. The brain is very sensitive to radiation effects, albeit as it is highly plastic. Hence, deleterious radiation effects may be potentially reversible. Because radiation exposure affects dendritic space, reduces the brain's ability to produce new neurons, and alters behavior, mitigation efforts should focus on restoring these parameters. To that effect, environmental enrichment through complex housing (CH) and exercise may provide a plausible avenue for exploration of protection from brain irradiation. CH is a much broader concept than exercise alone, and constitutes exposure of animals to positive physical and social stimulation that is superior to their routine housing and care conditions. We hypothesized that CHs may lessen harmful neuroanatomical and behavioural effects of low dose radiation exposure. We analyzed and compared cerebral morphology in animals exposed to low dose head, bystander (liver), and scatter irradiation on rats housed in either the environmental enrichment condos or standard housing. Enriched condo conditions ameliorated radiation-induced neuroanatomical changes. Moreover, irradiated animals that were kept in enriched CH condos displayed fewer radiation-induced behavioural deficits than those housed in standard conditions. Animal model-based environmental enrichment strategies, such as CH, are excellent surrogate models for occupational and exercise therapy in humans, and consequently have significant translational possibility. Our study may thus serve as a roadmap for the development of new, easy, safe and cost-effective methods to prevent and mitigate low-dose radiation effects on the brain.

Identification of Radiation-Induced miRNA Biomarkers Using the CGL1 Cell Model System.

MicroRNAs (miRNAs) have emerged as a potential class of biomolecules for diagnostic biomarker applications. miRNAs are small non-coding RNA molecules, produced and released by cells in response to various stimuli, that demonstrate remarkable stability in a wide range of biological fluids, in extreme pH fluctuations, and after multiple freeze–thaw cycles. Given these advantages, identification of miRNA-based biomarkers for radiation exposures can contribute to the development of reliable biological dosimetry methods, especially for low-dose radiation (LDR) exposures. In this study, an miRNAome next-generation sequencing (NGS) approach was utilized to identify novel radiation-induced miRNA gene changes within the CGL1 human cell line. Here, irradiations of 10, 100, and 1000 mGy were performed and the samples were collected 1, 6, and 24 h post-irradiation. Corroboration of the miRNAome results with RT-qPCR verification confirmed the identification of numerous radiation-induced miRNA expression changes at all doses assessed. Further evaluation of select radiation-induced miRNAs, including miR-1228-3p and miR-758-5p, as well as their downstream mRNA targets, Ube2d2, Ppp2r2d, and Id2, demonstrated significantly dysregulated reciprocal expression patterns. Further evaluation is needed to determine whether the candidate miRNA biomarkers identified in this study can serve as suitable targets for radiation biodosimetry applications.

Radioactive decay, health and social capital: Lessons from the Chernobyl experiment

We exploit the random variation in health patterns across European regions that resulted from the Chernobyl nuclear disaster to provide new quasi-experimental evidence on the causal effect of health patterns on social capital. Our instrumental variable estimations show that the radioactive fallout is positively associated with an increase in hospital discharges after treatment for neoplasms almost thirty years later, the magnitude of the effect being in line with other studies investigating the health effects of low-dose radiation exposure. An increased incidence of neoplasms in the local area of residence induced by the radioactive fallout, and the resulting perception of higher risks of contracting potentially deadly diseases among the healthy population, generates a sizeable impoverishment of social capital and a reduction in social interactions, altruism and happiness. Our findings suggest that health care and prevention policies may have additional returns in terms of a significant increase in communities’ social capital.

Extended analysis of solid cancer incidence among the Nuclear Industry Workers in the UK: 1955-2011.

Radiation worker studies provide direct estimates of cancer risk after protracted low-dose exposures to external X-ray and gamma-ray irradiations. The National Registry for Radiation Workers (NRRW) started in 1976 and has become the largest epidemiological program of research on nuclear workers in the UK. Here, we report on the relationship between solid cancer incidence and external radiation at the low-dose levels in 172,452 NRRW cohort members of whom (90%) were men. This study is based on 5.25 million person-years of follow-up from 1955 through the end of 2011. In the range of accumulated low doses two-thirds of workers have doses of less than 10 mSv. This study is an updated analysis of solid cancer incidence data with an additional 10 years of follow-up over the previous analysis of the NRRW cohort (NRRW-3). A total of 18,310 cases of solid cancers based on a 10-year lag were registered and of these 43% of the solid cancer cases occurred during the latest 10 years. Poisson regression was used to investigate the relationship between solid cancers risk and protracted chronic low-dose radiation exposure. This study demonstrated for solid cancers a rapid decrease of risk at high external doses that appeared to be driven by the workers who were monitored for potential exposure to internal emitters and who had also received relatively high external doses. Among cohort members only exposed to external radiation, a strong association was found between external dose and solid cancers (ERR/Sv = 0.52, 95% CI: 0.11; 0.96, based on 13,199 cases). A similar pattern is also seen for lung cancer. Excluding lung cancer from the grouping of all solid cancers resulted in evidence of a linear association with external radiation dose (ERR/Sv = 0.24, 95% CI: 0.01; 0.49, based on 15,035 cases), so suggesting some degree of confounding by smoking. Statistically significantly increasing trends with dose were seen for cancers of the colorectal, bladder and pleura cancer. Some of these results should be treated with caution because of the limited corroborating evidence from other published studies. Information on internal doses as well as non-radiation factors such smoking would be helpful to make more definitive inferences.

Ingestional Toxicity of Radiation-Dependent Metabolites of the Host Plant for the Pale Grass Blue Butterfly: A Mechanism of Field Effects of Radioactive Pollution in Fukushima.

Biological effects of the Fukushima nuclear accident have been reported in various organisms, including the pale grass blue butterfly Zizeeria maha and its host plant Oxalis corniculata. This plant upregulates various secondary metabolites in response to low-dose radiation exposure, which may contribute to the high mortality and abnormality rates of the butterfly in Fukushima. However, this field effect hypothesis has not been experimentally tested. Here, using an artificial diet for larvae, we examined the ingestional toxicity of three radiation-dependent plant metabolites annotated in a previous metabolomic study: lauric acid (a saturated fatty acid), alfuzosin (an adrenergic receptor antagonist), and ikarugamycin (an antibiotic likely from endophytic bacteria). Ingestion of lauric acid or alfuzosin caused a significant decrease in the pupation, eclosion (survival), and normality rates, indicating toxicity of these compounds. Lauric acid made the egg-larval days significantly longer, indicating larval growth retardation. In contrast, ikarugamycin caused a significant increase in the pupation and eclosion rates, probably due to the protection of the diet from fungi and bacteria. These results suggest that at least some of the radiation-dependent plant metabolites, such as lauric acid, contribute to the deleterious effects of radioactive pollution on the butterfly in Fukushima, providing experimental evidence for the field effect hypothesis.

Detection of biological responses to low-dose radiation in humans

It has been considered difficult to detect the biological effects of low-dose radiation exposure below approximately 100 mSv in humans. Serum proteomic analysis and oxidative modification profiling were conducted with blood samples collected from residents of a newly discovered high-level natural background radiation area (annual effective dose approximately 50 mSv y−1) and normal-level area (1.22 mSv y−1) in Mamuju, Indonesia, where many people have been living for generations. Dose-dependent oxidative modifications in amino acid sequences of human serum albumin, especially the 162nd and 356th tyrosine residues and 111th and 470th methionine residues, were found. None of these findings have been reported in humans exposed to chronic low-dose radiation. It can be used as a biomarker not only for the assessment of the presence or absence of radiation exposure but also for dose prediction in living organisms for chronic radiation. These results suggest that traces of radiation exposure are recorded in serum albumin and that there is a possibility of a new methodology that can evaluate biological responses below 100 mSv.

Addressing Risk Perceptions of Low-Dose Radiation Exposure.

Concern over low-dose radiation (LDR) (exposure of less than 100 milligray (mGy)) is resulting in people refusing diagnostic procedures and medical treatment 1 and also inhibiting revision of the linear no-threshold (LNT) assumption that informs much of science policy. This article reviews representative surveys in Ontario and Saskatchewan and focus groups conducted with science and policy stakeholders in addressing how the public and policy stakeholders understand issues of exposure to LDR and how policy issues can be addressed.Research results from focus groups demonstrated that policy stakeholders are knowledgeable about issues surrounding the public and perceptions about LDR and implications for policy consistent with LDR literature. Participants understood that the challenge went beyond providing more education about LDR and issues of emotions and biases must be addressed. This research resulted in rich suggestions for public communication and engagement surrounding LDR and a process for addressing the issue of the LNT.

Evidence-Based Imaging Guidelines for Chiropractic Biomechanical Spine Care, Reconsideration of X-Ray Exposure Risks, and Practical Applications of Research Evidence

First, the perceived risks of very low dose radiation exposures from x-rays in health care must be reconsidered with regard to their effects in humans. Second, a more practical application of data analyses from research is needed than the prevailing current approach. And third, the biomechanical conditions of previously injured spines in patients who present for chiropractic spine care should, when possible, be examined by imaging prior to applying forces from spinal manipulation or adjustments to ensure optimal safety and effectiveness.

THE INFLUENCE OF LOW-DOSE OCCUPATIONAL RADIATION EXPOSURE ON PERIPHERAL BLOOD CELLS IN A COHORT OF CHINESE MEDICAL RADIATION WORKERS

Abstract Objectives The study aims to assess the change of peripheral blood cell numbers following protracted low-dose radiation exposure among medical radiation workers. Methods A cohort of 375 Chinese medical workers were followed for 5 years (2015–19) and recorded the changes in blood cells and cumulative doses. T-test, least significant difference-T test, variance analysis and correlation analysis were utilized in this study. Results Compared with the control group, the white blood cells, hemoglobin counts and the ratio of eosinophils in the study group showed a downward trend. The differences in blood cells between groups were mainly found in the number of red blood cells. In a short cumulative time, such as 1 or 3 years, a correlation between the cumulative dose and the quantity of blood cells was detected, but not at 5 years. Conclusions There is no significant difference in the blood cell counts between different types of work, and the long-term cumulative dose has not been statistically correlated with the number of blood cells. So that the number of peripheral blood cells can no longer be used as a good indicator of radiation damage.

A Risk Comparison between Lifestyle, Socioeconomic Status, and Radiation: A Cohort Study of Cancer Mortality among Japanese Nuclear Workers (J-EPISODE).

The health effects of low-dose radiation exposure have been a source of controversy. One possible reason is that epidemiological studies that compare radiation risk with other factors, such as lifestyle or socioeconomic status, have been limited. The aim of this study is to conduct a comparison of the cancer risk of mortality between radiation, lifestyle habits (such as smoking), and socioeconomic status (such as years of education) among Japanese nuclear workers. We assembled a cohort of 41,742 male nuclear workers in Japan who answered a lifestyle questionnaire survey conducted during 2003-2004. To exclude systematic errors caused by missing values, we used multiple imputation and Poisson regression to estimate relative risks and confidence intervals for lifestyle habits, socioeconomic status, and radiation. The total person-y from 2005 to 2010 were 215,000. The mean age and cumulative dose were 54.9 y and 24.8 mSv (10-y lagged dose), respectively. Significantly high relative risks were determined for smoking, alcohol consumption, frequency of medical examination, breakfast intake, sleep, and body mass index. Further, significantly high relative risks of radiation were shown for lung cancer and smoking-related cancers. Since the simultaneous inclusion of radiation and non-radiation variables in the model for relative risk (RR) calculation means that the calculated radiation RR is the result of adjustment by other variables, the risk of cancer from low-dose radiation, if any, is less than smoking and probably less than other lifestyle factors.

Changes in Expression of Specific mRNA Transcripts after Single- or Re-Irradiation in Mouse Testes

Alkylating agents and irradiation induce testicular damage, which results in prolonged azoospermia. Even very low doses of radiation can significantly impair testis function. However, re-irradiation is an effective strategy for locally targeted treatments and the pain response and has seen important advances in the field of radiation oncology. At present, little is known about the relationship between the harmful effects and accumulated dose of irradiation derived from continuous low-dose radiation exposure. In this study, we examined the levels of mRNA transcripts encoding markers of 13 markers of germ cell differentiation and 28 Sertoli cell-specific products in single- and re-irradiated mice. Our results demonstrated that re-irradiation induced significantly decreased testicular weights with a significant decrease in germ cell differentiation mRNA species (Spo11, Tnp1, Gfra1, Oct4, Sycp3, Ddx4, Boll, Crem, Prm1, and Acrosin). In the 13 Sertoli cell-specific mRNA species decreased upon irradiation, six mRNA species (Claudin-11, Espn, Fshr, GATA1, Inhbb, and Wt1) showed significant differences between single- and re-irradiation. At the same time, different decreases in Sertoli cell-specific mRNA species were found in single-irradiation (Aqp8, Clu, Cst12, and Wnt5a) and re-irradiation (Tjp1, occludin, ZO-1, and ZO-2) mice. These results indicate that long-term aspermatogenesis may differ after single- and re-irradiated treatment.

Low-dose ionizing radiation exposure and risk of leukemia: results from 1950–1995 Chinese medical X-ray workers’ cohort study and meta-analysis

BackgroundIt has been well-established that acute radiation exposures increase the risk of leukemia. However, it is still unknown whether these leukemia risk estimates could be extrapolated to occupational populations who receive repeated low-dose radiation exposure. The purpose of this study was to estimate quantified associations between low-dose radiation exposures and leukemia. MethodsThe Chinese medical X-ray worker study (CMXW) included 27,011 medical X-ray workers employed at major hospitals in 24 provinces in China from 1950 to 1980, and a control population of 25,782 physicians matched by hospital, who were unexposed to X-ray equipment. Poisson regression models were used to estimate the excess relative risk (ERR) and excess absolute risk (EAR) for the incidence of leukemia associated with cumulative doses. A meta-analysis of the published literature on low-dose occupational radiation exposure and leukemia risk was also conducted. ResultsThe incidence rates of leukemia in X-ray workers and the control group were 6.70 and 3.39 per 100,000 person-years, respectively. Among X-ray workers, the average cumulative red bone marrow dose was 0.046 Gy. We found a positive relationship between 2-year lagged cumulative red bone marrow dose and risk of leukemia excluding chronic lymphocytic leukemia (CLL) (ERR = 0.66 per 100 mGy, 90% CI: 0.09, 1.53; EAR = 0.29 per 104 PY-100 mGy, 90% CI: 0.07, 0.56). The excess risk was largely driven by myeloid leukemia (ERR = 1.06 per 100 mGy, 90% CI: 0.22, 2.51). Based on the meta-analysis, the pooled ERR at 100 mGy was 0.19 (95% CI: 0.08, 0.31). ConclusionThis study provides strong evidence of a positive and linear doseresponse relationship between cumulative red bone marrow dose and the incidence of non-CLL leukemia.

Evaluation of risk due to chronic low dose ionizing radiation exposure on the birth prevalence of congenital heart diseases (CHD) among the newborns from high-level natural radiation areas of Kerala coast, India

BackgroundThe human population residing in monazite bearing Kerala coast are exposed to chronic low dose and low dose rate external gamma radiation due to Th232 deposits in its beach sand. The radiation level in this area varies from < 1.0 to 45.0 mGy/year. This area serves as an ideal source for conducting large-scale epidemiological studies for assessing risk of low dose and low dose rate radiation exposure on human population. The areas with a dose level of ≤1.50 mGy/year are considered as normal level natural radiation areas (NLNRAs) and areas with > 1.50 mGy/year, as high level natural radiation areas (HLNRAs). HLNRAs were further stratified into three dose groups of 1.51-3.0 mGy/year, 3.01-6.00 mGy/year and > 6.0 mGy/year. The present study evaluates the effects of chronic low dose radiation (LDR) exposure on the birth prevalence of Congenital Heart Diseases (CHD) among the live newborns monitored in hospital based prospective study from NLNRAs and HLNRAs of Kerala coast, India.MethodologyConsecutive newborns were monitored from two hospital units located in the study area for congenital malformations. Referred CHD cases among the newborns screened were confirmed by conducting investigations such as pulse oximetry, chest X-ray, electrocardiogram and echocardiogram etc.ResultsAmong the newborns screened, 289 CHDs were identified with a frequency of 1.49‰ among 193,634 livebirths, which constituted 6.03% of overall malformations and 16.29% of major malformations. Multiple logistic regression analysis suggested that the risk of CHD among the newborns of mothers from HLNRAs with a dose group of 1.51-3.0 mGy/year was significantly lower as compared to NLNRA (OR = 0.72, 95% CI: 0.57-0.92), whereas it was similar in HLNRA dose groups of 3.01-6.00 mGy/year (OR = 0.55, 95% CI: 0.31-1.00) and ≥ 6.0 mGy/year (OR = 0.96, 95% CI: 0.50-1.85). The frequency of CHDs did not show any radiation dose related increasing trend. However, a significant (P = 0.005) reduction was observed in the birth prevalence of CHDs among the newborns from HLNRA (1.28‰) as compared to NLNRA (1.79‰).ConclusionChronic LDR exposure did not show any increased risk on the birth prevalence of CHDs from high-level natural radiation areas of Kerala coast, India. No linear increasing trend was observed with respect to different background dose groups. The frequency of CHD was observed to be 1.49 per 1000 livebirths, which was similar to the frequency of severe CHD rate reported elsewhere in India and was much less than the reported frequency of 9 per thousand.

Low-dose radiation exposure and risk of pancreatic cancer among workers at nuclear power plants: a meta-analysis

Low-dose radiation exposure and risk of pancreatic cancer among workers at nuclear power plants: a meta-analysis