Stability of chromosome aberrations in the blood lymphocytes of astronauts measured after space flight by FISH chromosome painting

The Central Role of Cytogenetics in Radiation Biology

Radiation cytogenetics has a rich history seldom appreciated by those outside the field. Early radiobiology was dominated by physics and biophysical concepts that borrowed heavily from the study of radiation-induced chromosome aberrations. From such studies, quantitative relationships between biological effect and changes in absorbed dose, dose rate and ionization density were codified into key concepts of radiobiological theory that have persisted for nearly a century. This review aims to provide a historical perspective of some of these concepts, including evidence supporting the contention that chromosome aberrations underlie development of many, if not most, of the biological effects of concern for humans exposed to ionizing radiations including cancer induction, on the one hand, and tumor eradication on the other. The significance of discoveries originating from these studies has widened and extended far beyond their original scope. Chromosome structural rearrangements viewed in mitotic cells were first attributed to the production of breaks by the radiations during interphase, followed by the rejoining or mis-rejoining among ends of other nearby breaks. These relatively modest beginnings eventually led to the discovery and characterization of DNA repair of double-strand breaks by non-homologous end joining, whose importance to various biological processes is now widely appreciated. Two examples, among many, are V(D)J recombination and speciation. Rapid technological advancements in cytogenetics, the burgeoning fields of molecular radiobiology and third-generation sequencing served as a point of confluence between the old and new. As a result, the emergent field of "cytogenomics" now becomes uniquely positioned for the purpose of more fully understanding mechanisms underlying the biological effects of ionizing radiation exposure.

Cosmic chronometers: Is spaceflight a catalyst for biological ageing?

Astronauts returning from space missions often exhibit health issues mirroring age-related conditions, suggesting spaceflight as a potential driver of biological ageing and age-related diseases. To unravel the underlying mechanisms of these conditions, this comprehensive review explores the impact of the space "exposome" on the twelve hallmarks of ageing. Through a meticulous analysis encompassing both space environments and terrestrial analogs, we aim to decipher how different conditions influence ageing hallmarks. Utilizing PubMed, we identified 189 studies and 60 meet screening criteria. Research on biological ageing in space has focused on genomic instability, chronic inflammation, and deregulated nutrient sensing. Spaceflight consistently induces genomic instability, linked to prolonged exposure to ionizing radiation, triggers pro-inflammatory and immune alterations, resembling conditions in isolated simulations. Nutrient sensing pathways reveal increased systemic insulin-like growth-factor-1. Microbiome studies indicate imbalances favoring opportunistic species during spaceflight. Telomere dynamics present intriguing patterns, with lengthening during missions and rapid shortening upon return. Despite a pro-ageing trend, some protective mechanisms emerge. Countermeasures, encompassing dietary adjustments, prebiotics, postbiotics, symbiotics, tailored exercises, meditation, and anti-inflammatory supplements, exhibit potential. Spaceflight's impact on ageing is intricate, with diverse findings challenging established beliefs. Multidisciplinary studies provide guidance for future research in this field.

Carcinogenesis induced by space radiation: A systematic review

The carcinogenic risk from space radiation has always been a health risk issue of great concern during space exploration. In recent years, a large number of cellular and animal experiments have demonstrated that space radiation, composed of high-energy protons and heavy ions, has shown obvious carcinogenicity. However, different from radiation on Earth, space radiation has the characteristics of high energy and low dose rate. It is rich in high-atom-number and high-energy particles and, as it is combined with other space environmental factors such as microgravity and a weak magnetic field, the study of its carcinogenic effects and mechanisms of action is difficult, which leads to great uncertainty in its carcinogenic risk assessment. Here, we review the latest progress in understanding the effects and mechanisms of action related to cell transformation and carcinogenesis induced by space radiation in recent years and summarize the prediction models of cancer risk caused by space radiation and the methods to reduce the uncertainty of prediction to provide reference for the research and risk assessment of space radiation.

Genomic Changes Driven by Radiation-Induced DNA Damage and Microgravity in Human Cells

The space environment consists of a complex mixture of different types of ionizing radiation and altered gravity that represents a threat to humans during space missions. In particular, individual radiation sensitivity is strictly related to the risk of space radiation carcinogenesis. Therefore, in view of future missions to the Moon and Mars, there is an urgent need to estimate as accurately as possible the individual risk from space exposure to improve the safety of space exploration. In this review, we survey the combined effects from the two main physical components of the space environment, ionizing radiation and microgravity, to alter the genetics and epigenetics of human cells, considering both real and simulated space conditions. Data collected from studies on human cells are discussed for their potential use to estimate individual radiation carcinogenesis risk from space exposure.

The RABiT-II DCA in the Rhesus Macaque Model

An automated platform for cytogenetic biodosimetry, the "Rapid Automated Biodosimetry Tool II (RABiT-II)," adapts the dicentric chromosome assay (DCA) for high-throughput mass-screening of the population after a large-scale radiological event. To validate this test, the U.S. Federal Drug Administration (FDA) recommends demonstrating that the high-throughput biodosimetric assay in question correctly reports the dose in an in vivo model. Here we describe the use of rhesus macaques (Macaca mulatta) to augment human studies and validate the accuracy of the high-throughput version of the DCA. To perform analysis, we developed the 17/22-mer peptide nucleic acid (PNA) probes that bind to the rhesus macaque's centromeres. To our knowledge, these are the first custom PNA probes with high specificity that can be used for chromosome analysis in M. mulatta. The accuracy of fully-automated chromosome analysis was improved by optimizing a low-temperature telomere PNA FISH staining in multiwell plates and adding the telomere detection feature to our custom chromosome detection software, FluorQuantDic V4. The dicentric frequencies estimated from in vitro irradiated rhesus macaque samples were compared to human blood samples of individuals subjected to the same ex vivo irradiation conditions. The results of the RABiT-II DCA analysis suggest that, in the lymphocyte system, the dose responses to gamma radiation in the rhesus macaques were similar to those in humans, with small but statistically significant differences between these two model systems.

Simultaneous Exposure of Cultured Human Lymphoblastic Cells to Simulated Microgravity and Radiation Increases Chromosome Aberrations

During space travel, humans are continuously exposed to two major environmental stresses, microgravity (μG) and space radiation. One of the fundamental questions is whether the two stressors are interactive. For over half a century, many studies were carried out in space, as well as using devices that simulated μG on the ground to investigate gravity effects on cells and organisms, and we have gained insights into how living organisms respond to μG. However, our knowledge on how to assess and manage human health risks in long-term mission to the Moon or Mars is drastically limited. For example, little information is available on how cells respond to simultaneous exposure to space radiation and μG. In this study, we analyzed the frequencies of chromosome aberrations (CA) in cultured human lymphoblastic TK6 cells exposed to X-ray or carbon ion under the simulated μG conditions. A higher frequency of both simple and complex types of CA were observed in cells exposed to radiation and μG simultaneously compared to CA frequency in cells exposed to radiation only. Our study shows that the dose response data on space radiation obtained at the 1G condition could lead to the underestimation of astronauts' potential risk for health deterioration, including cancer. This study also emphasizes the importance of obtaining data on the molecular and cellular responses to irradiation under μG conditions.

Retrospective biodosimetry techniques: Focus on cytogenetics assays for individuals exposed to ionizing radiation

In the absence of physical data, biodosimetry tools are required for fast dose and risk assessment in the event of radiological or nuclear mass accidents or attacks to triage exposed humans and take immediate medical countermeasures. Biodosimetry tools have mostly been developed for retrospective dose assessment and the follow-up of victims of irradiation. Among them, cytogenetics analyses, to reveal chromosome damage, are the most developed and allow the determination of doses from blood samples as low as 100 mGy. Various cytogenetic tests have already allowed retrospective dose assessment of Chernobyl liquidators and military personnel exposed to nuclear tests after decades. In this review, we discuss the properties of various biodosimetry techniques, such as their sensitivity and limitations as a function of the time from exposure, using multiple examples of nuclear catastrophes or working exposure. Among them, chromosome FISH hybridization, which reveals chromosome translocations, is the most reliable due to the persistence of translocations for decades, whereas dicentric chromosome and micronuclei assays allow rapid and accurate dose assessment a short time after exposure. Both need to be adjusted through mathematical algorithms for retrospective analyses, accounting for the time since exposure and the victims' age. The goal for the future will be to better model chromosome damage, reduce the time to result, and develop new complementary biodosimetry approaches, such as mutation signatures.

Increased Chromosome Aberrations in Cells Exposed Simultaneously to Simulated Microgravity and Radiation

Space radiation and microgravity (μG) are two major environmental stressors for humans in space travel. One of the fundamental questions in space biology research is whether the combined effects of μG and exposure to cosmic radiation are interactive. While studies addressing this question have been carried out for half a century in space or using simulated μG on the ground, the reported results are ambiguous. For the assessment and management of human health risks in future Moon and Mars missions, it is necessary to obtain more basic data on the molecular and cellular responses to the combined effects of radiation and µG. Recently we incorporated a μG⁻irradiation system consisting of a 3D clinostat synchronized to a carbon-ion or X-ray irradiation system. Our new experimental setup allows us to avoid stopping clinostat rotation during irradiation, which was required in all other previous experiments. Using this system, human fibroblasts were exposed to X-rays or carbon ions under the simulated μG condition, and chromosomes were collected with the premature chromosome condensation method in the first mitosis. Chromosome aberrations (CA) were quantified by the 3-color fluorescent in situ hybridization (FISH) method. Cells exposed to irradiation under the simulated μG condition showed a higher frequency of both simple and complex types of CA compared to cells irradiated under the static condition by either X-rays or carbon ions.

Effects of High- and Low-LET Radiation on Human Hematopoietic System Reconstituted in Immunodeficient Mice

Over the last 50 years, a number of important physiological changes in humans who have traveled on spaceflights have been catalogued. Of major concern are the short- and long-term radiation-induced injuries to the hematopoietic system that may be induced by high-energy galactic cosmic rays encountered on interplanetary space missions. To collect data on the effects of space radiation on the human hematopoietic system in vivo, we used a humanized mouse model. In this study, we irradiated humanized mice with 0.4 Gy of 350 MeV/n ²⁸Si ions, a dose that has been shown to induce tumors in tumor-prone mice and a reference dose that has a relative biological effectiveness of 1 (1 Gy of 250-kVp X rays). Cell counts, cell subset frequency and cytogenetic data were collected from bone marrow spleen and blood of irradiated and control mice at short-term (7, 30 and 60 days) and long-term ( 6 - 7 months) time points postirradiation. The data show a significant short-term effect on the human hematopoietic stem cell counts imparted by both high- and low-LET radiation exposure. The radiation effects on bone marrow, spleen and blood human cell counts and human cell subset frequency were complex but did not alter the functions of the hematopoietic system. The long-term data acquired from high-LET irradiated mice showed complete recovery of the human hematopoietic system in all hematopoietic compartments. The combined results demonstrate that, in spite of early perturbation, the longer term effects of high-LET radiation are not detrimental to human hematopoiesis in our system of study.

Vive la radiorésistance!: converging research in radiobiology and biogerontology to enhance human radioresistance for deep space exploration and colonization

While many efforts have been made to pave the way toward human space colonization, little consideration has been given to the methods of protecting spacefarers against harsh cosmic and local radioactive environments and the high costs associated with protection from the deleterious physiological effects of exposure to high-Linear energy transfer (high-LET) radiation. Herein, we lay the foundations of a roadmap toward enhancing human radioresistance for the purposes of deep space colonization and exploration. We outline future research directions toward the goal of enhancing human radioresistance, including upregulation of endogenous repair and radioprotective mechanisms, possible leeways into gene therapy in order to enhance radioresistance via the translation of exogenous and engineered DNA repair and radioprotective mechanisms, the substitution of organic molecules with fortified isoforms, and methods of slowing metabolic activity while preserving cognitive function. We conclude by presenting the known associations between radioresistance and longevity, and articulating the position that enhancing human radioresistance is likely to extend the healthspan of human spacefarers as well.

Cosmic-ray interaction data for designing biological experiments in space

There is growing interest in flying biological experiments beyond low-Earth orbit (LEO) to measure biological responses potentially relevant to those expected during a human mission to Mars. Such experiments could be payloads onboard precursor missions, including unmanned private-public partnerships, as well as small low-cost spacecraft (satellites) designed specifically for biosentinel-type missions. It is the purpose of this paper to provide physical cosmic-ray interaction data and related information useful to biologists who may be planning such experiments. It is not the objective here to actually design such experiments or provide radiobiological response functions, which would be specific for each experiment and biological endpoint. Nuclide-specific flux and dose rates were calculated using OLTARIS and these results were used to determine particle traversal rates and doses in hypothetical biological targets. Comparisons are provided between GCR in interplanetary space and inside the ISS. Calculated probabilistic estimates of dose from solar particle events are also presented. Although the focus here is on biological experiments, the information provided may be useful for designing other payloads as well if the space radiation environment is a factor to be considered.

Three-dimensional normal human neural progenitor tissue-like assemblies: a model of persistent varicella-zoster virus infection

Varicella-zoster virus (VZV) is a neurotropic human alphaherpesvirus that causes varicella upon primary infection, establishes latency in multiple ganglionic neurons, and can reactivate to cause zoster. Live attenuated VZV vaccines are available; however, they can also establish latent infections and reactivate. Studies of VZV latency have been limited to the analyses of human ganglia removed at autopsy, as the virus is strictly a human pathogen. Recently, terminally differentiated human neurons have received much attention as a means to study the interaction between VZV and human neurons; however, the short life-span of these cells in culture has limited their application. Herein, we describe the construction of a model of normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs), which can be successfully maintained for at least 180 days in three-dimensional (3D) culture, and exhibit an expression profile similar to that of human trigeminal ganglia. Infection of NHNP TLAs with cell-free VZV resulted in a persistent infection that was maintained for three months, during which the virus genome remained stable. Immediate-early, early and late VZV genes were transcribed, and low-levels of infectious VZV were recurrently detected in the culture supernatant. Our data suggest that NHNP TLAs are an effective system to investigate long-term interactions of VZV with complex assemblies of human neuronal cells.

Varicella-zoster virus (VZV), the alphaherpesvirus that typically causes childhood chickenpox and shingles in adults, becomes latent in neurons, thus remaining in the body for a lifetime. Unfortunately, few models are available to study the establishment of VZV latency since the virus infects only humans and establishes persistent infections and latency only in neurons, a slowly proliferating, short-lived cell in culture. We have successfully maintained normal human neural progenitor cells (NHNP) in tissue-like assemblies (TLAs) in 3-dimensional (3D) cultures for up to 6 months. The 3D NHNP TLAs show some characteristics as those found in the human trigeminal ganglia, the site of VZV latency. NHNP TLAs infected with VZV remain viable for 3 months during which time VZV DNA replicates and remains genetically stable, virus genes are transcribed, and infectious VZV is sporadically released. The ability to maintain VZV infected NHNP cells in culture for extended times provides the unique opportunity to study the molecular interactions between this important human pathogen and neuronal tissue to an extent previously unattainable.

Effects of (12)C(6+) ion radiation and ferulic acid on the zebrafish (Danio rerio) embryonic oxidative stress response and gene expression

The effects of carbon ion irradiation and ferulic acid (FA) on the induction of oxidative stress and alteration of gene expression were studied in zebrafish (Danio rerio) embryos. Zebrafish embryos at 8 hpf were divided into seven groups: the control group; the 1Gy, 3Gy and 7Gy irradiation groups; and three FA-pre-treated irradiation groups. In the irradiated groups, a significant increase in the teratogenesis of the zebrafish embryos and oxidative stress was accompanied by increased malondialdehyde (MDA) content, decreased glutathione (GSH) content and alterations in antioxidant enzyme activities (such as catalase [CAT] and superoxide dismutase [SOD]). Moreover, the mRNA levels for Cu/Zn-sod, Mn-sod, cat and gpx, the genes encoding these antioxidant proteins, were altered significantly. However, the mRNA expression patterns were not in accordance with those of the antioxidant enzymes and were more sensitive under low-dose irradiation. In addition, we detected the mRNA expression of ucp-2 and bcl-2, which are located at the mitochondrial inner membrane and related to reactive oxidative species (ROS) production. In the irradiated groups, the mRNA level of ucp-2 was significantly increased, whereas the mRNA level of bcl-2 was significantly decreased. Supplementation with FA, an antioxidant, was better able to reduce the irradiation-induced oxidative damage marked by changes in mortality, morphology, antioxidant enzyme activities and the MDA and GSH content, as well as in the mRNA expression levels. Overall, this study provided helpful information about the transcriptional effects of irradiation to better understand the mechanism of carbon ion-induced oxidative stress and FA-induced radioprotective effects.

Expression of p53-regulated proteins in human cultured lymphoblastoid TSCE5 and WTK1 cell lines during spaceflight

The aim of this study was to determine the biological effects of space radiations, microgravity, and the interaction of them on the expression of p53-regulated proteins. Space experiments were performed with two human cultured lymphoblastoid cell lines: one line (TSCE5) bears a wild-type p53 gene status, and another line (WTK1) bears a mutated p53 gene status. Under 1 gravity or microgravity conditions, the cells were grown in the cell biology experimental facility (CBEF) of the International Space Station for 8 days without experiencing the stress during launching and landing because the cells were frozen during these periods. Ground control samples were simultaneously cultured for 8 days in the CBEF on the ground for 8 days. After spaceflight, protein expression was analyzed using a Panorama(TM) Ab MicroArray protein chips. It was found that p53-dependent up-regulated proteins in response to space radiations and space environment were MeCP2 (methyl CpG binding protein 2), and Notch1 (Notch homolog 1), respectively. On the other hand, p53-dependent down-regulated proteins were TGF-β, TWEAKR (tumor necrosis factor-like weak inducer of apoptosis receptor), phosho-Pyk2 (Proline-rich tyrosine kinase 2), and 14-3-3θ/τ which were affected by microgravity, and DR4 (death receptor 4), PRMT1 (protein arginine methyltransferase 1) and ROCK-2 (Rho-associated, coiled-coil containing protein kinase 2) in response to space radiations. ROCK-2 was also suppressed in response to the space environment. The data provides the p53-dependent regulated proteins by exposure to space radiations and/or microgravity during spaceflight. Our expression data revealed proteins that might help to advance the basic space radiation biology.

Chromosomal aberrations in the bone marrow cells of mice induced by accelerated (12)C(6+) ions

The whole bodies of 6-week-old male Kun-Ming mice were exposed to different doses of (12)C(6+) ions or X-rays. Chromosomal aberrations of the bone marrow (gaps, terminal deletions and breaks, fragments, inter-chromosomal fusions and sister-chromatid union) were scored in metaphase 9h after exposure, corresponding to cells exposed in the G(2)-phase of the first mitosis cycle. Dose-response relationships for the frequency of chromosomal aberrations were plotted both by linear and linear-quadratic equations. The data showed that there was a dose-related increase in the frequency of chromosomal aberrations in all treated groups compared to controls. Linear-quadratic equations were a good fit for both radiation types. The compound theory of dual radiation action was applied to decipher the bigger curvature (D(2)) of the dose-response curves of X-rays compared to those of (12)C(6+) ions. Different distributions of the five types of aberrations and different degrees of homogeneity were found between (12)C(6+) ion and X-ray irradiation and the possible underlying mechanism for these phenomena were analyzed according to the differences in the spatial energy deposition of both types of radiation.

Frozen human cells can record radiation damage accumulated during space flight: mutation induction and radioadaptation

To estimate the space-radiation effects separately from other space-environmental effects such as microgravity, frozen human lymphoblastoid TK6 cells were sent to the "Kibo" module of the International Space Station (ISS), preserved under frozen condition during the mission and finally recovered to Earth (after a total of 134 days flight, 72 mSv). Biological assays were performed on the cells recovered to Earth. We observed a tendency of increase (2.3-fold) in thymidine kinase deficient (TK(-)) mutations over the ground control. Loss of heterozygosity (LOH) analysis on the mutants also demonstrated a tendency of increase in proportion of the large deletion (beyond the TK locus) events, 6/41 in the in-flight samples and 1/17 in the ground control. Furthermore, in-flight samples exhibited 48% of the ground-control level in TK(-) mutation frequency upon exposure to a subsequent 2 Gy dose of X-rays, suggesting a tendency of radioadaptation when compared with the ground-control samples. The tendency of radioadaptation was also supported by the post-flight assays on DNA double-strand break repair: a 1.8- and 1.7-fold higher efficiency of in-flight samples compared to ground control via non-homologous end-joining and homologous recombination, respectively. These observations suggest that this system can be used as a biodosimeter, because DNA damage generated by space radiation is considered to be accumulated in the cells preserved frozen during the mission, Furthermore, this system is also suggested to be applicable for evaluating various cellular responses to low-dose space radiation, providing a better understanding of biological space-radiation effects as well as estimation of health influences of future space explores.

Biological effects of space radiation on human cells: history, advances and outcomes

Exposure to radiation is one of the main concerns for space exploration by humans. By focusing deliberately on the works performed on human cells, we endeavored to review, decade by decade, the technological developments and conceptual advances of space radiation biology. Despite considerable efforts, the cancer and the toxicity risks remain to be quantified: 1) the nature and the frequency of secondary heavy ions need to be better characterized in order to estimate their contribution to the dose and to the final biological response; 2) the diversity of radiation history of each astronaut and the impact of individual susceptibility make very difficult any epidemiological analysis for estimating hazards specifically due to space radiation exposure. 3) Cytogenetic data undoubtedly revealed that space radiation exposure produce significant damage in cells. However, our knowledge of the basic mechanisms specific to low-dose, to repeated doses and to adaptive response is still poor. The application of new radiobiological techniques, like immunofluorescence, and the use of human tissue models different from blood, like skin fibroblasts, may help in clarifying all the above items.

Chromosome translocations and assessing human exposure to adverse environmental agents

This article discusses the use of chromosome translocations for assessing adverse environmental exposure in humans. Translocations are a persistent biomarker of exposure and a biomarker of effect, making them the endpoint of choice for certain human exposure studies because they indicate a potential relationship between exposure and adverse health outcomes, particularly cancer and birth defects. Presented here are the different types of translocations, their origins and persistence, the strengths and limitations of using translocations for exposure assessments, the current state of the art for quantifying exposure including the importance of confounding effects, and the use of model organisms. This article concludes with an assessment of the future of translocation analyses.

Radon and leukemia in the Danish study: another source of dose

An epidemiologic study of childhood leukemia in Denmark (2,400 cases; 6,697 controls) from 1968 to 1994 suggested a weak, but statistically significant, association of residential radon exposure and acute childhood lymphoblastic leukemia (ALL). The Danish study estimated a relative risk (RR) = 1.56 (95% CI, 1.05-2.30) for a cumulative exposure of 1,000 Bq m-3 y. For an exposure duration of 10 y their RR corresponds to a radon concentration of 100 Bq m-3. There are two dose pathways of interest where alpha particles could damage potential stem cells for ALL. One is the alpha dose to bone marrow, and two is the dose to bronchial mucosa where an abundance of circulating lymphocytes is found. Compared with an exposure of about 1 mSv y-1 from natural external background, radon and decay products contribute an additional 10 to 60% to the bone marrow equivalent dose. The other pathway for exposure of T (or B) lymphocytes is within the tracheobronchial epithelium (BE). Inhaled radon decay products deposit on the relatively small area of airway surfaces and deliver a significant dose to the nearby basal or mucous cells implicated in human lung cancer. Lymphocytes are co-located with basal cells and are half as abundant. Using a 10-y exposure to 100 Bq m-3, our dose estimates suggest that the equivalent dose to these lymphocytes could approach 1 Sv. The relatively high dose estimate to lymphocytes circulating through the BE, potential precursor cells for ALL, provides a dose pathway for an association.

Heavy ion carcinogenesis and human space exploration

Before the human exploration of Mars or long-duration missions on the Earth's moon, the risk of cancer and other diseases from space radiation must be accurately estimated and mitigated. Space radiation, comprised of energetic protons and heavy nuclei, has been shown to produce distinct biological damage compared with radiation on Earth, leading to large uncertainties in the projection of cancer and other health risks, and obscuring evaluation of the effectiveness of possible countermeasures. Here, we describe how research in cancer radiobiology can support human missions to Mars and other planets.

Environmental exposure to carcinogenic polycyclic aromatic hydrocarbons—The interpretation of cytogenetic analysis by FISH

The capital city of Prague is one of the most polluted localities of the Czech Republic. The effect of exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) adsorbed onto respirable air particles (<2.5 microm) on chromosomal aberrations was studied in a group of city policemen (street patrol, aged 34+/-8 years) working in the downtown area of Prague and spending daily >8h outdoors (N=61) in months of January and March 2004. Ambient air particles (PM10, PM2.5) and c-PAHs were monitored using Versatile Air Pollution Sampler (VAPS), and personal exposure was evaluated using personal samplers during working shift. Chromosomal aberrations were analyzed by fluorescent in situ hybridization (FISH) and conventional cytogenetic analysis. Urinary cotinine, plasma levels of vitamins A, E and C, folate, total cholesterol, HDL, LDL cholesterols and triglycerides were also analyzed as possible effect modifiers. During the sampling period the particulate air pollution monitored by VAPS was in January versus March as follows: PM10 55.6 microg/m3 versus 36.4 microg/m3, PM2.5 44.4 microg/m3 versus 24.8 microg/m3, c-PAHs 19.7 ng/m3 versus 3.6 ng/m3, and B[a]P 4.3 ng/m3 versus 0.8 ng/m3. Significant differences were observed for all FISH endpoints studied for the sampling in January and March (%AB.C.=0.27+/-0.18 versus 0.16+/-0.17, p<0.001, F(G)/100=1.32+/-1.07 versus 0.85+/-0.95, p<0.01, AB/1000 (aberrations/1000 cells)=4.27+/-3.09 versus 2.59+/-2.79, p<0.001) while conventional cytogenetic analysis did not reveal any differences in the frequency of chromosomal aberrations. Factors associated with an increased level of translocations by FISH indicated the effect of age, cholesterol, LDL-cholesterol and vitamin C. We may conclude that FISH indicates that the city policemen in Prague represent a group of increased genotoxic risk. This is the first study reporting that translocations induced by c-PAHs in peripheral lymphocytes last only several weeks.

Getting ready for the manned mission to Mars: the astronauts' risk from space radiation

Space programmes are shifting towards planetary exploration and, in particular, towards missions by human beings to the Moon and to Mars. Radiation is considered to be one of the major hazards for personnel in space and has emerged as the most critical issue to be resolved for long-term missions both orbital and interplanetary. The two cosmic sources of radiation that could impact a mission outside the Earth's magnetic field are solar particle events (SPE) and galactic cosmic rays (GCR). Exposure to the types of ionizing radiation encountered during space travel may cause a number of health-related problems, but the primary concern is related to the increased risk of cancer induction in astronauts. Predictions of cancer risk and acceptable radiation exposure in space are extrapolated from minimal data and are subject to many uncertainties. The paper describes present-day estimates of equivalent doses from GCR and solar cosmic radiation behind various shields and radiation risks for astronauts on a mission to Mars.

Biomarkers of space radiation risk

Radiation risk estimates are based on epidemiological data obtained on Earth for cohorts exposed predominantly to acute doses of gamma rays, and the extrapolation to the space environment is highly problematic and error-prone. The uncertainty can be reduced if risk estimates are compared directly to space radiation-induced biological alterations, i.e. by detecting biomarkers in astronauts. Chromosomal aberrations in peripheral blood lymphocytes are the only biomarker that can provide simultaneous information on dose, dose equivalent and risk, and they have been measured extensively in astronauts during the past 10 years. Individual relative risks calculated from chromosomal aberration measurements in crew members after single space missions in low-Earth orbit fall in the same range as the estimates derived from physical dosimetry, suggesting that the current system for radiogenic risk evaluation is essentially sound. However, the output of the biomarker test is dependent upon the sampling time. Recent results show a fast time-dependent decay of chromosomal aberrations in blood lymphocytes after space flight and a lack of correlation between translocations and cumulative dose in astronauts involved in two to five space missions. This "time factor" may reflect individual variability and time dependence in the risk produced by exposure to cosmic radiation during the flight. Biomarkers may be superior to dose in predicting space radiation risk, pending technical improvements in sensitivity, and validation by epidemiological studies.