A SYSTEMATIC REVIEW OF THE TOXICOLOGICAL EFFECTS AND EXPOSURE ROUTES OF NUCLEAR AND IONIZING RADIATION ON CELLULAR, GENETIC, AND ECOLOGICAL HEALTH

Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [197] A SYSTEMATIC REVIEW OF THE TOXICOLOGICAL EFFECTS AND EXPOSURE ROUTES OF NUCLEAR AND IONIZING RADIATION ON CELLULAR, GENETIC, AND ECOLOGICAL HEALTH Jannene L. Alam1 Ivar T. Dajac1 Fiona Eunice R. Gasis1 Crisha Marie P. Salamat1 Gecelene C. Estorico1,2 Civil and Allied Department; Environmental Science and Chemical Technology Department 1Technological University of the Philippines - Taguig Metro Manila 1630, Philippines 2De La Salle University - Dasmariñas, Cavite, DBB-B, 4115 West Ave., Dasmariñas ABSTRACT This systematic review examines the toxicological effects of ionizing radiation, specifically gamma rays and Xrays, across cellular, organismal, and ecological levels. The purpose of the study was to consolidate recent scientific findings to clarify radiation-induced mechanisms, exposure pathways, and dose-related outcomes. A comprehensive search following PRISMA guidelines was conducted across Google Scholar, ScienceDirect, PubMed, Web of Science, and SpringerLink, focusing on studies published from 2015 to 2025. Twenty peerreviewed articles met the inclusion criteria, representing in vitro experiments, in vivo investigations, and ecological field studies. Results show that ionizing radiation consistently produces molecular disruptions such as DNA strand breaks, oxidative stress, chromosomal abnormalities, genomic instability, and bystander signaling. In vivo evidence demonstrates that both acute and chronic exposures impair neurogenesis, alter epigenetic patterns, reduce organ function, and increase long-term cancer risk, with effects influenced by dose, exposure duration, and biological sensitivity. Ecological studies conducted in radiation-affected regions, including Chernobyl and Fukushima, report increased mutation rates, reduced fertility, disrupted population dynamics, and in several species, transgenerational genetic changes. Although certain organisms exhibit resilience linked to ecological conditions or life-history traits, most show measurable biological stress under prolonged exposure. These findings indicate that ionizing radiation produces dose-dependent and context-dependent effects that range from molecular injury to ecosystem-level consequences. The review emphasizes the value of integrating cellular, organismal, and ecological evidence for improving risk assessment and radiation protection and highlights the need for continued interdisciplinary research to better understand low-dose exposures, enhance environmental monitoring, and guide public health and ecological management. Keywords: Ionizing Radiation, Toxicological Effects, DNA Damage, Ecological Health, Radiation Exposure Pathways INTRODUCTION Since Wilhelm Roentgen’s discovery of X-rays in 1895 and Marie Curie’s pioneering research on radioactivity, ionizing radiation has become central to medicine, industry, and energy production. Gamma and X-rays, in particular, have revolutionized diagnostic imaging, cancer therapy, and scientific investigation. However, their capacity to alter atomic and molecular structures also presents significant toxicological and ecological hazards. As both beneficial tools and potential environmental stressors, these high-energy radiations warrant a comprehensive examination of their biological and ecological implications (Corredor et al., 2018). Ionizing radiation refers to electromagnetic or particulate energy with sufficient force to remove tightly bound electrons from atoms, producing ions that destabilize molecular structures. Gamma rays and X-rays (forms of electromagnetic ionizing radiation) are distinguished by their origin: gamma rays are emitted from the atomic nucleus, while X-rays arise from electronic transitions or deceleration processes such as bremsstrahlung. Their Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [198] high penetration power enables them to traverse tissues and materials, depositing energy that can disrupt biological molecules, most notably DNA. According to the Agency for Toxic Substances and Disease Registry (ATSDR, 1999), such interactions can lead to oxidative stress, cellular apoptosis, chromosomal aberrations, and mutagenesis that contribute to carcinogenesis and heritable genetic defects At the cellular and molecular levels, ionizing radiation inflicts damage both directly (by ionizing DNA molecules) and indirectly through the generation of reactive oxygen species that oxidize cellular components. These processes can cause singleand double-strand DNA breaks, base modifications, and chromosomal translocations, disrupting replication and repair mechanisms (ATSDR, 1999). When these damages persist, they may result in genomic instability, uncontrolled proliferation, or programmed cell death. Historically, epidemiological data from radiation-exposed populations such as Hiroshima and Nagasaki survivors and radium dial painters have demonstrated strong doseresponse relationships between radiation exposure and elevated cancer incidence. Similarly, Corredor et al. (2018) emphasized that even low-level occupational exposures among military and healthcare workers require strict monitoring, as chronic exposure can produce cumulative stochastic effects, including cancer and hereditary abnormalities. Beyond human health, the ecological consequences of ionizing radiation have become increasingly evident. Radioactive isotopes released into the environment can travel through air, soil, and water, integrating into food chains and bioaccumulating in plants and animals. The ATSDR (1999) noted that radionuclides such as cesium137 and strontium-90 persist in ecosystems, where they interfere with reproduction, development, and genetic stability of wildlife populations. Long-term environmental studies following the Chernobyl and Fukushima disasters have revealed that chronic low-dose radiation can disrupt population dynamics, alter genetic diversity, and induce physiological stress in both terrestrial and aquatic organisms. These findings underscore that radiation exposure extends far beyond immediate health risks, posing systemic threats to biodiversity and ecosystem resilience. Despite extensive historical research, significant knowledge gaps remain in understanding the mechanistic, temporal, and ecological dimensions of ionizing radiation toxicity. The interplay between exposure parameters (such as dose, dose rate, radiation quality, and exposure duration) continues to challenge predictive toxicology. Moreover, integrated studies that connect molecular-level damage to organismal and ecosystem-level outcomes remain limited (Corredor et al., 2018; ATSDR, 1999). The primary objective of this systematic review is to comprehensively evaluate the toxicological effects of gamma and X-ray ionizing radiation on cellular, genetic, and ecological systems reported between 2015 and 2025. Specifically, the review aims to synthesize and compare existing studies that investigated radiationinduced biological outcomes, including DNA damage, oxidative stress, apoptosis, mutagenesis, and physiological or ecological impacts across various organisms and ecosystems. It further seeks to identify the key mechanisms of radiation toxicity (spanning molecular, biochemical, and cellular pathways) and to examine how exposure parameters such as radiation type, dose, dose rate, and duration influence these outcomes. Additionally, this review intends to evaluate the primary exposure routes and pathways through which gamma and X-ray radiation affect organisms and ecosystems, highlighting both direct and indirect effects. Finally, the study aims to consolidate current understanding of dose-response relationships, long-term health consequences, and ecological implications of ionizing radiation, thereby providing evidence-based insights for improved risk assessment, safety standards, and future research directions. This review endeavors to bridge the gap between toxicological, environmental, and radiobiological disciplines. By systematically integrating findings across cellular, genetic, and ecological levels, it seeks to elucidate the mechanisms by which gamma and X-ray radiation exert their effects and to advance a holistic understanding of ionizing radiation’s impact on biological integrity and environmental sustainability. OBJECTIVES The primary objective of this systematic review is to comprehensively evaluate the toxicological effects of gamma and X-ray ionizing radiation on cellular, genetic, and ecological systems reported between 2015 and 2025. Specifically, the review aims to synthesize and compare existing studies that investigated radiationinduced biological outcomes, including DNA damage, oxidative stress, apoptosis, mutagenesis, and physiological or ecological impacts across various organisms and ecosystems. It further seeks to identify the key mechanisms of radiation toxicity, including molecular, biochemical, and cellular pathways, and to examine how exposure parameters such as radiation type, dose, dose rate, and duration influence these outcomes. Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [199] Additionally, the review intends to evaluate primary exposure routes and pathways through which gamma and X-ray radiation affect organisms and ecosystems, highlighting both direct and indirect effects. Finally, this study aims to consolidate current understanding of dose-response relationships, long-term health consequences, and ecological implications of ionizing radiation, thereby providing evidence-based insights for risk assessment, safety standards, and future research directions. METHODOLOGY This The study utilized a systematic review approach design. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines to ensure methodological rigor. The protocol guided the identification, screening, eligibility assessment, and inclusion of peer-reviewed literature addressing the toxicological effects, exposure routes, and ecological consequences of gamma and X-ray ionizing radiation published between 2015 and 2025. Data Sources A comprehensive and systematic search of published studies was conducted to gather reliable evidence on the cellular, genetic, and ecological impacts of gamma and X-ray radiation. Academic databases including Google Scholar, ScienceDirect, PubMed, Web of Science, and SpringerLink were searched. All retrieved studies were assessed using the PRISMA framework to ensure consistency in methodology, traceability of article selection, and reproducibility of results. Literature Search To ensure broad coverage and avoid missing relevant studies, searches used key terms and Boolean operators such as AND and OR. Multiple keyword combinations were employed to retrieve pertinent literature. The first set of terms targeted phytoremediation mechanisms and plant species, incorporating keywords such as “Ionizing radiation,” “gamma radiation,” “X-ray radiation,” “Toxicity,” “cellular effects,” “DNA damage,” “Oxidative stress,” “Ecological exposure,” “environmental effects,” and “radiation pathway.” To align the study with contemporary research trends, Searches were restricted to peer-reviewed journal articles and scientific studies published from 2015 to 2025 that matched the predefined keywords. Additionally, to provide comprehensive background information, supplementary reference materials such as books and technical reports were considered for conceptual grounding but not included in the final synthesis unless they met inclusion criteria. During the initial screening phase, all retrieved publications were assessed based on their titles, authors, publication metadata, and source journals to eliminate duplicates. Irrelevant studies were subsequently excluded, while the remaining articles that met relevance criteria were then subjected to full-text review to ensure alignment with the study objectives. Inclusion and Exclusion Criteria This review systematically evaluated relevant literature using predefined inclusion and exclusion criteria to ensure the quality, accuracy, and relevance of the selected studies. Studies were included if they: (1) were original research articles or peer-reviewed scientific papers, published between 2015–2025; (2) all studies were required to match predefined keywords related to ionizing radiation toxicity; (3) were available in full-text and written in English; and (4) focused specifically on the toxicological effects of gamma and X-ray radiation, including cellular, genetic, or ecological outcomes; (5) Reported quantitative parameters, such as radiation dose (Gy/mGy), exposure duration, dose–response relationships, biomarker or genotoxicity results, or ecological toxicity measurements. Additionally, studies examining mechanistic pathways such as oxidative stress induction, DNA repair response, or ecological bioaccumulation were considered relevant. Studies were excluded if they: (1) were review articles, conference abstracts, or opinion papers without original data; (2) did not include quantitative biological or toxicological measurements; (3) focused on other radiation types; (4) were published before 2015; (5) were not available in English or as full-text publications; or (6) examined radiation exposure only from a theoretical or engineering standpoint, without assessing biological, cellular, genetic, or ecological effects. Furthermore, studies with insufficient methodological detail, unclear radiation dosage reporting, or lacking appropriate control groups were excluded to ensure scientific rigor and comparability among the selected research. Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [200] Search Results A total of 82 studies were initially identified using the predefined search terms across five academic databases, including Google Scholar, ScienceDirect, Web of Science, PubMed, and SpringerLink. To ensure relevance to the research objectives, the search was restricted to peer-reviewed scientific articles published in English between 2015 and 2025, focusing specifically on ionizing radiation, toxicological effects, cellular/genetic damage, and ecological exposure pathways. During the preliminary filtering, 18 studies were excluded because they were outside the year range, written in non-English languages, or lacked direct relevance to ionizing radiation biological effects. After removing 12 duplicate records, 52 studies remained for title and abstract screening. Screening was performed using the predefined inclusion criteria, which required studies to: (1)investigate gamma and/or X-ray radiation exposure; (2) evaluate cellular, genetic, physiological, or ecological effects; (3) provide measurable or quantitative toxicological data; and (4) describe mechanisms of radiation toxicity or exposure pathways. Based on these criteria, 17 studies were excluded due to insufficient quantitative data, focus on non-ionizing radiation, or studies limited to theoretical modeling or instrument calibration without biological assessment. The remaining 35 full-text articles were assessed for eligibility. Of these, 15 were excluded due to incomplete data sets, lack of methodological detail, absence of control groups, and unavailability of full-text versions. Ultimately, 20 studies met all inclusion criteria and were included in the qualitative synthesis. The identification, screening, eligibility assessment, and final inclusion procedure is summarized in the PRISMA flow diagram (Figure 1). Figure 1. Stages of Study Selection and Results Presented in the PRISMA Flow Diagram Data Extraction Data extraction was performed using a pre-designed and standardized extraction form to ensure consistency and completeness of information gathered from each included study. From every article, bibliographic information Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [201] such as the authors, year of publication, country of origin, and journal source were recorded. Details regarding study design, including whether the study was conducted at the cellular, organismal, or ecological level (in vitro, in vivo, or field-based), were documented. Key experimental parameters related to radiation exposure were extracted, including the radiation type (gamma or X-ray), source of radiation (medical, industrial, or researchbased), exposure dose (Gy or mGy), duration and frequency of exposure, dose-rate, and the characterization of control or comparison groups (non-irradiated controls or sham-exposed samples). Biological endpoints relevant to toxicological evaluation were captured, such as DNA damage assessment (comet assay, γ-H2AX foci formation, micronucleus test, chromosomal aberrations), oxidative stress indicators (reactive oxygen species levels, antioxidant enzyme activity, lipid peroxidation), cellular or physiological responses (apoptosis rates, cell viability, reproductive success, mortality), and ecological or population-level effects where applicable. Quantitative outcomes, including mean values, fold-changes, and dose-response relationships, were extracted along with reported measures of variability such as standard deviation, standard error, or confidence intervals, together with the number of replicates and the statistical analyses used. To evaluate study quality and transparency in methodology, additional information was recorded regarding sample size justification, randomization procedures, blinding of outcome assessment, and the availability of supplementary or raw data. Two reviewers independently performed data extraction for all included studies, and inconsistencies were resolved through discussion, with arbitration by a third reviewer when necessary. All extracted data were stored in a master spreadsheet and cross-checked against the full-text articles. When essential numerical values or methodological details were missing or unclear, attempts to contact corresponding authors were made and documented in an extraction log. Risk of Bias Assessment Risk of bias for all included studies was evaluated using a modified assessment tool adapted for toxicology and ionizing radiation research, incorporating principles from established critical appraisal checklists used in laboratory, environmental, and health-related experimental studies. The assessment examined whether the radiation source and exposure parameters (gamma or X-ray type, dose, dose rate, and duration) were clearly defined and justified, and whether the biological model used (cell line, organism, or ecological sample) was adequately characterized and representative. The evaluation also considered allocation and comparability of experimental groups, including the presence of appropriate control groups such as non-irradiated or shamexposed samples. Performance bias was assessed by determining whether the experimental conditions including temperature, radiation calibration, exposure geometry, and shielding were consistent across replicates and sufficiently described to allow reproducibility. Detection bias was examined by assessing whether outcome measurements, such as genotoxicity assays, oxidative stress markers, or ecological response indicators, used validated analytical methods and whether outcome assessors were blinded to treatment conditions when possible. Reporting bias was evaluated based on the completeness of outcome reporting, transparency in handling excluded samples or missing data, and whether prespecified outcomes were consistently reported. Statistical and analytical rigor was assessed by documenting replication, statistical tests used, measures of variability, and whether dose–response analyses were performed. Finally, external and ecological validity were considered by examining whether results were generated under real-world exposure scenarios or limited to strictly controlled laboratory settings. Each study was graded as having low, moderate, or high risk of bias, with justification provided for each rating. Two reviewers independently conducted the assessment, and disagreements were resolved through discussion or by involving a third reviewer when necessary. Common issues across the body of evidence included insufficient reporting of radiation calibration and dose-rate measurements, lack of replication or absence of variance reporting, short exposure durations that limited interpretation of long-term or cumulative biological effects, and limited ecological validity due to many studies being conducted exclusively under controlled laboratory conditions. These bias assessments informed how individual findings were weighted in the narrative synthesis and guided subgroup considerations, such as comparing high versus low-bias studies when interpreting dose-response relationships. Although the adapted tool addressed key internal validity concerns within ionizing radiation research, subjectivity in reviewer judgment and heterogeneity in experimental techniques across studies limited full quantitative harmonization of bias ratings. Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [202] RESULTS AND DISCUSSION Overview of the Included Studies This review compiled 20 experimental studies investigating the toxicological effects and exposure pathways of Nuclear and Ioninzing radiation, specifically Gamma and X-ray across different contexts, which are cellular, genetic and ecological. The matrix (Table 1) summarizes the essential parameters of these studies, including Radiation Type & Exposure matrix, Study type, Exposure pathways, Cellular/Genetic Findings, and Ecological Findings & Mechanisms. These compiled data offer a clear overview of how experimental research on the radiation’s potential toxicity has progressed and where variations in findings arise Table 1. Summary of Related Studies on the toxicological effects of Nuclear and Ionizing Radiation Radiation Type & Exposure Metric Study Type Subject Exposure Pathways Cellular/Genetic Findings Ecological Findings & Mechanisms Author and Year Gamma (Chronic, ambient) Ecological Wolves (Chernoby l Exclusion Zone) External exposure from territory; internal exposure from ingesti on of contaminated prey. N/A (Population Study) Thriving wolf population, suggesting potential benefits (e.g., absence of humans) can outweigh radiation costs in some contexts. Fuller et al. (2015) Gamma (Dose rates from 0.1 µGy/h to 100 mGy/h) Ecological Wildlife (Chernoby l & Fukushima ) Multiple pathways: External irradiation from ground/air, internal irradiation from inhalation & ingestion of radionuclides (e.g., Cs-137, I-131). N/A (Metaanalysis) Derived species-specific dose-effect relationships. Chronic dose rates > 0.1 mGy/h can reduce survival & reproduction. Mechanis m: Combined internal and external radiotoxicity. GarnierLaplace et al. (2015) X-rays (0.1-2 Gy) In vivo (Rodents) Rat Thyroid Localized, external irradiation targeted at the thyroid gland. Non-linear gene expression response; low doses could induce protective pathways while high doses induced damagerelated pathways. N/A - Mechanism: Hormetic effect at very low doses vs. toxic effect at higher doses from localized exposure. Sokolov & Neumann (2016) Gamma (Cs137 from sediment) Ecological Aquatic crustacean s (Lake) Internal exposure from ingesti on of contaminated algae and sediment; external exposure from water and sediment. N/A (Field measurement & lab experiment) No observed effect on population-level endpoints despite internal dose from Cs137. Highlights complexity of field studies. Strand et al. (2017) Gamma/Beta (Chronic, field doses) Ecological Scots pine (Chernoby l) External exposure from deposition & internal exposure from root uptake of radionuclides (e.g., Sr-90, Cs-137). Increased frequency of mutations and cytogenetic abnormalities in meristematic cells. Morphological abnormalities and reduced reproductive capacity. Geras'kin et al. (2017) Gamma (Ambient, Ecological Birds & Insects External exposure from N/A (Field census) Significant decline in abundance and Møller et al. (2018) Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [203] dose rate) (Chernoby l) deposited radionuclides on plumage and habitat; internal exposure from ingestion of contaminated food. fertility across multiple taxa with increasing radiation dose. Mechanism: Acute and chronic stress from combined exposure pathways. Gamma-rays (Chronic, 0.04 mGy/h; Acute, 1 Gy) In vivo Laboratory Mice Whole-body, uniform external irradiation in a controlled laboratory setting. Chronic exposure led to persistent epigenetic changes (DNA methylation) in the liver, distinct from acute exposure signatures. N/A - Mechanism: Epigenetic reprogramming as a long-term consequence of chronic low-dose exposure. Sokolov et al. (2019) Gamma/Beta (Environment al fallout) Ecological Pale Grass Blue Butterfly (Fukushim a) Internal exposure from ingesti on of contaminated leaves by larvae; external exposure of all life stages. Accumulation of genetic mutations over multiple generations in contaminated fields, leading to increased abnormality rates. Transgenerational genomic instability observed in successive generations. Mechanism: Internal emitters causing heritable germline mutations. Hiyama et al. (2020) X-rays (Cumulative dose from CT scans) In vivo (Huma n) Pediatric patients (CT scans) Localized, partialbody external irradiation from medical imaging, with dose concentrated in the scanned region (head/body). Positive association between radiation dose from CT scans and risk of leukaemia and brain tumours. N/A - Mechanism: Carcinogenesis from localized, high-dose medical exposure. Hauptmann et al. (2020) Gamma/Beta (Chronic, ambient) Ecological Plants & Animals (Chernoby l) For animals: ingestion of contaminated food, inhalation of dust. For plants: root uptake and aerial deposition. Increased mutation rates and oxidative stress across diverse species. Reduced brain size, sperm quality, and biodiversity. Mechanism: Oxidative stress and genetic damage from chronic internal and external exposure. Mousseau & Møller (2020) Gamma (Chronic, dose gradient) Ecological Soil invertebrat es (Chernoby l) External exposure from contaminated soil & internal exposure from ingestion of contaminated soil and organic matter. N/A (Field study) No consistent negative effect on soil fauna abundance across multiple taxa, suggesting high resilience at current field doses. Beresford et al. (2020) X-rays (Low dose, 0.1 Gy) In vitro Human bronchial epithelial Direct, localized external irradiation of cell culture, with Induced senescence and a proinflammatory N/A - Mechanism: Radiation-induced bystander effect via Lacombe et al. (2021) Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [204] cells study of bystander pathway via culture medium transfer. secretome (SASP). Promoted neoplastic transformation in neighboring cells. paracrine signaling. X-rays (0.5-2 Gy) In vivo (Rodent) Mouse neural stem cells Whole-body, uniform external irradiation. Impaired neurogenesis and cognitive function linked to persistent DNA damage and microglial activation in the hippocampus. Long-term cognitive deficits in learning and memory tasks. Mechanism: Neural stem cell apoptosis and neuroinflammation. Barazzuol et al. (2021) X-rays (0.5-2 Gy) In vitro Human peripheral blood mononucle ar cells Direct, uniform external irradiation of blood samples. Dose-dependent increase in γ-H2AX foci and chromosomal aberrations. Showe d inter-individual variability in DNA damage response. N/A - Mechanism: Direct DNA damage and variable efficiency of DNA repair machinery across individuals. Graw et al. (2021) Gamma-rays (0.5-5 Gy) In vitro Human endothelial cells Direct irradiation of donor cells; soluble factor-mediated pathway to receiver cells via medium transfer. Confirmed and characterized radiation-induced bystander effects, including genomic instability and reduced cell viability in recipient cells. N/A - Mechanism: Communication of damage signals via soluble factors in the extracellular environment. Lumniczky et al. (2021) Gamma-rays (1-4 Gy) In vitro Human and mouse cells Direct, uniform external irradiation of cell culture. Detailed the role of specific DNA repair protein deficiencies (e.g., DNA-PKcs) in driving genomic instability after radiation. N/A - Mechanism: Elucidated the molecular mechanism of errorprone DNA repair leading to mutations. Mladenov et al. (2022) X-rays (2-8 Gy) In vitro Human lung cancer cells Direct, uniform external irradiation of cell culture. Activation of cGAS-STING pathway by cytosolic DNA fragments, driving radiation-induced inflammation, senescence, and cell death. N/A - Mechanism: Links DNA damage to innate immune response and tissue injury. Tang et al. (2022) Gamma-rays (Low dose, 0.1 Gy) In vitro Human dermal fibroblasts Direct, uniform external irradiation of cell culture. Induced a transient adaptive response, upregulati ng antioxidant genes (e.g., NRF2). N/A - Mechanism: Biphasic dose-response; low-dose hormesis vs. high-dose toxicity via oxidative stress. Byun et al. (2023) Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [205] Higher doses (1 Gy) caused sustained oxidative stress and senescence. X-rays (2-8 Gy) In vitro Patientderived cancer organoids Direct, uniform external irradiation of 3D tissue models. Demonstrated that the SASP from irradiated cancerassociated fibroblasts promotes therapy resistance in tumor cells. N/A - Mechanism: Bystander signaling in the tumor microenvironment contributing to treatment failure. Lacombe et al. (2023) Gamma (Cs137, chronic ingestion) Ecological Wild boar (Fukushim a and Chernobyl ) Internal exposure from ingesti on of contaminated roots, fungi, and soil. N/A (Field measurement) Persistently high contamination levels providing insights into long-term bioaccumulation and ecosystem cycling of radionuclides. Jones et al. (2024) Table 1 consolidates findings from twenty peer-reviewed studies investigating the toxicological effects of nuclear and ionizing radiation—specifically gamma and X-rays—across cellular, genetic, and ecological scales. The matrix presents each study’s exposure parameters, biological subjects, pathways of exposure, and mechanistic outcomes. Collectively, these studies reveal that both acute and chronic exposures to ionizing radiation produce measurable biological and ecological consequences, governed largely by dose intensity, exposure duration, and biological susceptibility. Across the dataset, gamma radiation is the most frequently examined type due to its prevalence in environmental contamination from nuclear incidents such as Chernobyl and Fukushima. X-rays, in contrast, are primarily employed in controlled in vitro and in vivo models to investigate molecular and cellular mechanisms of toxicity. Exposure routes among ecological studies often involve both external irradiation from environmental deposition and internal exposure through ingestion or inhalation of radionuclides like Cs-137, Sr-90, and I-131. Laboratory studies predominantly utilize localized or whole-body external exposure, enabling controlled dose–response analysis. A consistent trend identified in the table is the dose-dependent biphasic nature of radiation toxicity. Several studies reported hormetic responses at very low doses (≤0.1 Gy), where limited radiation exposure stimulated antioxidant defenses and DNA repair pathways (Sokolov & Neumann, 2016; Byun et al., 2023). However, with increasing dose or chronic exposure, these adaptive mechanisms were overwhelmed, leading to oxidative stress, genomic instability, and cell senescence. Cellular-level experiments confirmed these effects through biomarkers such as γ-H2AX foci formation, chromosomal aberrations, and activation of the cGAS–STING pathway (Graw et al., 2021; Tang et al., 2022). Additionally, studies on the radiation-induced bystander effect revealed that non-irradiated neighboring cells could exhibit DNA damage and inflammatory signaling, indicating the role of paracrine and extracellular communication in amplifying toxicity (Lacombe et al., 2021; Lumniczky et al., 2021). At the ecological scale, the summarized studies demonstrate substantial variability in organismal responses to chronic field exposure. Research in the Chernobyl and Fukushima exclusion zones highlights that chronic gamma and beta radiation induces mutations, oxidative stress, and reproductive impairments across multiple taxa, including plants, insects, and vertebrates (Møller et al., 2018; Geras’kin et al., 2017; Mousseau & Møller, 2020). Nonetheless, some species exhibited ecological resilience or population stability despite contamination, as observed in soil invertebrates and wolves (Beresford et al., 2020; Fuller et al., 2015). This variation reflects the influence of ecological context, life history traits, and potential adaptive mechanisms in modulating radiation Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [212] In conclusion, the ecological evidence summarized in Table 5 highlights the systemic and long-term effects of nuclear and ionizing radiation across diverse ecosystems. By linking radiation exposure to genomic instability, oxidative stress, reproductive impairment, and population dynamics, these studies elucidate the toxicokinetics of radiation in real-world ecological contexts, providing essential insights for environmental risk assessment, conservation management, and understanding the broader biological consequences of chronic ionizing radiation. Synthesis and Implications The collective evidence from in vitro, in vivo, and ecological studies underscores the multifaceted toxicological impact of ionizing radiation, particularly gamma rays and X-rays, across biological scales. In vitro studies reveal consistent cellular and genetic responses, including DNA damage, oxidative stress, senescence, and bystander effects, demonstrating how even localized irradiation can propagate molecular dysfunction beyond directly exposed cells. Mechanistic pathways such as activation of the cGAS–STING axis, SASP, and error-prone DNA repair are recurrently observed, illustrating the molecular underpinnings of radiation-induced cellular injury. Dose, exposure duration, and cell type strongly influence these outcomes, highlighting the importance of context in interpreting radiation toxicity. In vivo investigations expand these molecular insights to organismal effects, revealing how radiation exposure affects specific organs and systemic health outcomes. Studies in rodents and pediatric patients show that lowdose exposures can elicit adaptive, protective responses, whereas higher or cumulative doses induce persistent DNA damage, epigenetic modifications, impaired neurogenesis, and increased cancer risk. Whole-body versus localized irradiation paradigms further illustrate how exposure route modulates both immediate and delayed toxic effects. These findings bridge molecular damage observed in vitro with clinically relevant physiological and neurological consequences, providing a critical link between cellular mechanisms and organismal health. Ecological studies provide a complementary perspective by situating radiation toxicity within real-world environmental contexts. Populations of plants, invertebrates, and vertebrates in Chernobyl and Fukushima exhibit varying resilience, with genomic instability, oxidative stress, reproductive impairment, and transgenerational effects reported across taxa. Observed outcomes are shaped by dose gradients, chronicity, exposure pathways, and species-specific sensitivity, with some populations (e.g., wolves) thriving under chronic contamination due to ecological factors such as human absence. These studies highlight the systemic and longterm ecological implications of radiation, extending the scope of toxicokinetic understanding from individual organisms to populations and ecosystems. A cross-cutting theme across these studies is the doseand context-dependent nature of radiation toxicity. At low doses, organisms may activate repair and adaptive pathways that mitigate damage, whereas higher or prolonged exposures overwhelm repair mechanisms, leading to cumulative DNA lesions, oxidative stress, and systemic dysfunction. The bystander effect, transgenerational instability, and epigenetic reprogramming illustrate that radiation effects are not confined to directly exposed cells or individuals, emphasizing the broader systemic and ecological reach of ionizing radiation. These mechanisms collectively inform both human health risk assessment and environmental management of contaminated areas. Overall, the integration of molecular, organismal, and ecological evidence advances a holistic understanding of radiation toxicokinetics and systemic impacts. The findings have significant implications for radiation protection, medical imaging and therapy, environmental monitoring, and conservation strategies. Recognizing the interplay between exposure dose, route, duration, and organismal sensitivity is critical for predicting outcomes and mitigating risks. This synthesis emphasizes the necessity of multi-level, interdisciplinary approaches to fully capture the complex biological consequences of nuclear and ionizing radiation. ACKNOWLEDGEMENT The researchers wish to convey their sincere appreciation to the faculty of the Civil and Allied Department, as well as the Environmental Science and Chemical Technology Department, for their continuous academic support and valuable guidance throughout the conduct of this systematic review. The authors also express their deepest gratitude to their adviser, Ms. Gecelene Estorico, whose professional insight, constructive feedback, and dedicated mentorship significantly contributed to the quality and completion of this work. Lastly, the Volume-09 Issue 11, November-2025 ISSN: 2456-9348 Impact Factor: 8.232 International Journal of Engineering Technology Research & Management (IJETRM) https://ijetrm.com/ IJETRM (http://ijetrm.com/) [213] researchers acknowledge the collective effort of the entire research team, whose cooperation, commitment, and sense of shared responsibility were integral to the successful completion of this study. CONCLUSION This systematic review provides strong evidence that ionizing radiation, particularly gamma rays and X-rays, affects biological systems across multiple levels of organization. Findings from cellular and molecular studies show that radiation consistently causes DNA strand breaks, oxidative stress, chromosomal abnormalities, and disruptions in the mechanisms responsible for maintaining genomic stability. These effects activate pathways related to senescence, inflammation, and modified gene expression, while also influencing how cells communicate with one another through bystander signaling. The reviewed studies make it clear that dose, exposure duration, and biological sensitivity are central factors determining whether cells mount adaptive responses or progress toward irreversible damage. At moderate to high doses, the capacity for repair is generally exceeded, leading to persistent genetic instability and increased likelihood of carcinogenic and degenerative processes. In vivo research further expands this understanding by demonstrating how these cellular effects translate into measurable physiological and developmental outcomes. Rodent models show that both chronic low-dose and acute high-dose exposures can alter neurogenesis, modify epigenetic patterns, impair organ function, and increase susceptibility to disease. Human-based evidence, particularly from pediatric imaging studies, confirms that repeated or concentrated exposure elevates long-term health risks such as cancer and neurological impairment. The diversity of these results reflects the complexity of ionizing radiation’s action in whole organisms, where factors such as tissue type, developmental stage, and exposure route shape the severity and nature of toxic effects. Together, the in vivo findings demonstrate that the impacts of radiation extend well beyond immediate cellular injury, influencing systemic processes and long-term health trajectories. Ecological studies add another dimension by showing how ionizing radiation affects entire populations and ecosystems over extended periods. Research conducted in Chernobyl, Fukushima, and other contaminated environments reveals that plants, insects, birds, mammals, and aquatic organisms experience increased mutation rates, reduced reproductive success, altered behavior, and in some cases transgenerational genetic changes. While certain species have maintained stable populations due to ecological advantages or reduced human disturbance, many others show clear signs of biological stress and disrupted population dynamics. These ecological patterns, when viewed alongside molecular and organismal data, highlight radiation as a stressor capable of shaping both short-term biological responses and long-term ecological outcomes. 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