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Summary, Conclusions, and Implications
Published in T. D. Luckey, Radiation Hormesis, 2020
Recommended standards for future supplementation and safety limits (Table 9.2) were derived from reasonable interpolation with extrapolation between background studies with humans and ZEP as determined in animals. The comments indicate conditions where the different dose rates may be expected. The most important are the optimal rate of 100 mGy/y as a recommended allowance, the acceptable rate of 1 Gy/y as a work limit, and the maximal rate of 10 Gy/y as a health limit. Animal studies, indicate a conservative estimation of ZEP to be about 10 Gy/y; although this should not be exceeded, the present interpretation is that this would provide no serious detriment to health. The chronic radiation syndrome at 100 Gy/y has been studied in animals; many of these results could probably be extrapolated to humans. The highest dose rate listed, 1 kGy/y, wold soon produce an acute radiation syndrome. This dose rate connects the extensive literature on the harmful effects of ionizing radiation with the information in this critical review on the effects of chronic and acute exposures of low doses of ionizing radiation in mammals.
Effects of chronic exposure to low levels of IR on Medaka (Oryzias latipes): a proteomic and bioinformatic approach
Published in International Journal of Radiation Biology, 2021
Yeni Natalia C. Perez-Gelvez, Alvin C. Camus, Robert Bridger, Lance Wells, Olin E. Rhodes, Carl W. Bergmann
For any IR exposure, the outcomes and types of symptoms depend on the parameters of the exposure. Acute exposure to relatively mild doses (0.3–0.5 Gy) may result in nausea, vomiting, and a decrease in blood counts, while higher doses (more than 1 Gy) may have neurological and cardiovascular impacts and potentially fatal consequences (Anno et al. 1989; Donnelly et al. 2010). When exposure is very low during the acute phase, symptoms may appear months to years later, a phenomenon known as chronic radiation syndrome (CRS). CRS usually occurs following an annual whole-body radiation exposure above 0.7 Gy with accumulative doses >2–3 Gy in a period of 2–3 years (Stewart et al. 2012; Akleyev 2014). Further, after disasters such as those at Chernobyl and Fukushima, trans-generational effects may occur, often with higher frequency than predicted by the current models (Omar-Nazir et al. 2018), or may not happen as new data shows (Yeager et al. 2021). While the benefits of the use of low doses of IR in medicine are undeniable, such exposures also have the potential to cause detrimental long-term health effects (Vaiserman et al. 2018). For example, multiple CT scans in pediatric diagnostics can result in damage to organs and increase the risk of cancer (UNSCEAR 2000; Ogbole 2010; Miglioretti et al. 2013). However, the benefits of CT scans usually outweigh the possible risks of radiation exposure. A similar situation occurs with radiotherapy, thus the detrimental effects of such an approach must be weighed against the potential increase in life span in oncology patients. This balance between risk and reward points to the need for a deeper understanding of the effects of chronic exposure to low-dose IR.
Utility of gene expression studies in relation to radiation exposure and clinical outcomes: thyroid cancer in the Ukrainian-American cohort and late health effects in a MAYAK worker cohort
Published in International Journal of Radiation Biology, 2021
Michael Abend, Ruth M. Pfeiffer, Matthias Port, Maureen Hatch, Tetyana Bogdanova, Mykola D. Tronko, Kiyohiko Mabuchi, Tamara Azizova, Kristian Unger, Herbert Braselmann, Patrick Ostheim, Alina V. Brenner
In our recently published work, we performed a gene expression study on a group of Mayak workers who were exposed either to combined internal alpha particles due to incorporated Plutonium-239 (239Pu) and external gamma rays, or to external gamma rays only (Abend et al. 2014a, 2014b; Abend, Azizova, et al. 2015). Peripheral blood was taken from workers older than 70 years of age, suffering from 29 different chronic diseases such as atherosclerotic disease or diabetes. We conducted a two-phase study. For phase I, we screened the whole genome for radiation-associated candidate genes and identified 25 mRNAs and 20 miRNAs species. Within the following validation step, we employed another methodology (quantitative real time PCR, qRT-PCR), used 92 blood samples from different individuals, and adjusted each of the radiation-to-gene models for 26 potential confounders such as age at biosampling, lifestyle factors (smoking, alcohol), and health status indicators (diastolic/systolic blood pressure, body mass index, atherosclerosis, etc.). We then examined whether significant dose-to-gene relationships remained after considering all potential confounders. Ultimately, 15 mRNA and 15 miRNAs showed statistically significant dose-to-gene relationship following adjustments (Figure 3, upper panel). After identification of genes presumably related to radiation exposure (dose-to-gene associations), we wondered about the clinical significance of the genés altered gene expression (gene-to-disease associations). Hence, in the next phase of our study (phase II), we sought to determine the clinical significance of altered gene expression for 15 validated mRNAs and 15 miRNAs. Specifically, we tested the association between altered gene expression intensity and risk of chronic disease other than cancer employing more complex mathematical models. We examined the association of Phase I-identified radiation-associated genes with the 29 different chronic diseases from which the Mayak workers were suffering. Altogether, 12 mRNAs and 9 miRNAs appeared to be significantly associated with 6 diseases, including chronic radiation syndrome, thyroid disease, increased blood pressure, atherosclerotic disease and others (Figure 3, lower panel). In particular, HNRNPA1, RAPGEF1 and SERPINB9 appeared to be very promising molecular targets; these were further confirmed by a bioinformatic approach which emphasized their impact on the atherosclerotome (Abend, Azizova, et al. 2015). These findings are currently being validated in a prospective cohort study of the Ukrainian Chernobyl clean-up workers.