Effect of combined radioactive and chemical (heavy metals,herbicides) pollution on the yield of cytogenetic disruptions in the intercalary meristem of spring barley

The yield of aberrant cells and their loading with lesions of intercalary meristem of spring barley in conditions of the combined action of 137Cs, heavy metals and 2.4-D herbicide was studied. At simultaneous insertion of 137Cs and Cd into the soil, the type of non-linearity of the yield of aberrant cells was determined by radioactive pollution: in a range of low concentrations the synergistic effects took place, in a range of higher ones the antagonistic effects did. In the presence of cadmium, the severity of radiation induced damage to aberrant cells was significantly less. The interaction in 137Cs-Pb pair had an antagonistic character. The yield of aberrant cells was determined mainly by lead, whereas the radioactive pollution played the main role in loading of the aberrant cells with lesions. At the combined pollution with 137Cs and other contaminants, the antagonistic effects were more pronounced with Pb than with Cd, and further increased with the herbicide, both in the test on frequency of aberrant cells and the test on the loading of aberrant cells with lesions. In case of combination of the chemical agents the non-linear effects in test on loading of aberrant cells with lesions were mainly synergistic, whereas in the test on frequency of aberrant cells they were antagonistic. Only Pb-Cd pair and only in the test on loading of aberrant cells with lesions no significant non-linear effects were found. The results show high rate of the induction of synergistic and antagonistic effects in conditions of the combined action of low concentrations of the investigated agents on plants. These effects substantially determined the yield of cytogenetic disturbances in the studied range.     

Cytogenetic effects of combined radioactive (137Cs) and chemical (Cd, Pb, and 2,4-D herbicide) contamination on spring barley intercalar meristem cells

The frequency of cytogenetic effects in spring barley intercalar meristem cells was studied in the presence of a range of different stressors. There was a non-linear dependence on the concentrations of 137Cs, Cd, Pb, and dichlorophenoxyacetic acid (2,4-D) herbicide contamination in the exposure ranges used. The frequency of cytogenetic effects increased at the lower concentrations of the pollutants more rapidly than at the higher concentrations. Contamination of the soil by lead at a concentration that meets the current standards for permissible content in soil, and by 2,4-D herbicide at the application levels recommended for agricultural use resulted in a significant increase in aberrant cell frequency. In these cases, the extent of the observed cytogenetic effects was comparable with the effect induced by a 137Cs soil contamination of 49.2 kBq/kg, a level that exceeds by 10-fold the maximum level permitted in radionuclide-contaminated areas where people are resident. In most cases, the experimentally observed combined effects of the pollutants studied differed from those expected from an additive hypothesis. When combined with 137Cs contamination, antagonistic effects became increasingly stronger when the second stressor was changed from cadmium to lead, and then to the herbicide, as measured both by tests of the 'frequency of aberrant cells' and the 'aberrations per cell'. Data from this study and previous reported literature suggest that synergistic increases in cytogenetic effects can be induced by the simultaneous influence of several stressors even at low intensities. This indicates that there is a capability for mutual intensification of the effects of environmental factors that actually occur in situations of low-level exposure.     

The problem of the transgeneration phenomenon of genome instability in sick children of different age groups after the accident at the Chernobyl Nuclear Power Plant

A complex genetic examination of children which belong to two cohorts and their parents were carried out. The first cohort included children and constantly living on territories contaminated with radionuclides (Novozybkov district, Bryansk region). They were subdivided in groups according to the ontogenetic age periods of development of their parents at the time of the Chernobyl accident. In the children born in 1986-1995 the level of aberrant genomes is significantly higher as compared to the control (p < 0.001). In children born in 1998-2002 the differences are insignificant (p > 0.05). The frequency of aberrant genomes had a tendency to decrease with the period of time between the birth date of a child and the moment of the accident. Analysis of the results of cytogenetic investigation for the same living on territories with different densities of radioactive contamination (zone I-- 627-688 kBq/m2, 137Cs and zone II-- 135-402 kBq/m2, 137Cs) revealed insignificant differences in the spectrum and average frequencies of chromosome aberrations. The second cohort included children born in 1987-1991 and 1993-2002 from irradiated fathers (Chernobyl clean-up workers) and unirradiated mothers living on territories without radionuclide contamination. These children also displayed increased frequencies of aberrant genomes as compared to the control (p < 0.001). The analysis of the dynamics years of birth of cytogenetic disturbances in the same cohorts of children showed the average frequencies of aberrant genomes remain higher than the control level. In most of the children of both cohorts the repair synthesis of genome DNA by gamma- and UV-radiation is reduced as compared to one in the children from the control group.     

Dose responses for chromosome aberrations produced in noncycling primary human fibroblasts by alpha particles,and by gamma rays delivered at sublimiting low dose rates

As the total dose of X or gamma rays is delivered at lower and lower rates, the yield of chromosome aberrations progressively diminishes. Simultaneously, the shape of the dose response changes from one exhibiting pronounced upward curvature at high dose rates to one approaching linearity at low dose rates. Although the maximum sparing effect caused by lowering the dose rate can be predicted from classical cytogenetic theory, it has yet to be verified experimentally. Here, noncycling normal human fibroblasts were exposed to graded doses of (137)Cs gamma rays at chronic dose rates of 6.3 and 2.8 cGy h(-1), dose rates that we reasoned should be lower than those required to achieve maximal sparing. This was indeed shown to be the case, after it was determined that the two chronic dose rates produced identical linear dose responses of 0.05 total aberrations per cell Gy(-1). Consistent with cytogenetic theory, this value was statistically indistinguishable from the linear coefficient derived from a fit to aberration frequencies produced by high-dose-rate exposure. Exposure to (238)Pu alpha particles also produced a linear dose response for total aberrations, whose slope-with respect to (137)Cs gamma rays as a reference radiation-implied a maximum RBE of 35 +/- 2.     

Relation of the antitumor activity of 4'-epidoxorubicin and cytogenetic disorders of tumor cells in experimental studies

Antitumor and cytogenetic activities of 4-epi-doxorubicin (EDR), an anthracycline antibiotic, were studied on female Wistar rats with transplantable ascitic ovary tumor (OT). It was shown that after a single administration in a dose of 3 mg/kg, EDR prolonged the average lifespan of the tumor-bearing rats by 213.4 per cent as compared to that in the controls. The maximum number of the aberrant cells in the bone marrow was observed 24 hours after injection of EDR. In 6 day it decreased to the control level. The maximum increase in the number of the OT aberrant cells was recorded 2 days after EDR injection and even in 10 days the number of the aberrant cells amounted to 20.2 +/- 1.3 per cent. It is suggestive of a high selective action of EDR and relation between the EDR antitumor activity and the disturbances in the chromosomal apparatus of the OT cells.     

Results of dynamic cytogenetic study of children and teenagers living in areas, radioactive by contaminated after the Chernobyl accident

Results of multiyear cytogenetic study of children and teenagers living in areas, radioactive by contaminated after Chernobyl accident, were adduced. Mean density of 137Cs contamination in two compared living areas were 111 and 200 kBq/m2 and mean external doses accumulated for 1986-2001 were 6.7 and 11.4 mGy correspondingly. Averaged thyroid doses receives by subjects of all age groups in the second area were approximately 1.5 times higher than in the first area; in the youngest group (0-1 year) the doses were 114.3 and 174.3 mGy. During 17 years cytogenetic investigation approximately from 30% to 60% of examined persons were observed the increased level of chromosome aberrations in lymphocytes of peripheral blood. Average frequency of unstable aberrations (acentrics, dicentrics and centric rings) constituted about 0.4 per 100 cells (0.22 per 100 cells in controls) during all period of observation. Level of marker aberrations (dicentrics and centric rings) was increased almost all times of study and varied within 0.04-0.19 per 100 cell (0.03 in control group). The parallel investigation of frequency of stable aberrations by FISH method showed up their level about 3 times exceeding observed dicentrics level. Comparably higher indexes of cytogenetic disturbances were revealed in group exposed in utero during period of accident.     

Variability of water content and of depth profiles of global fallout 137Cs in grassland soils and the resulting external gamma-dose rates

¹³⁷Cs from global fallout of nuclear weapon testings in the 1950s and 1960s was determined in successive layers (0–30 cm) of eight undisturbed grassland soils in Bavaria, Germany. The maximum activity concentration was found in soil layers between 4 and 15 cm below the surface. Using the vertical distribution of the cesium activity, which varied considerably from site to site, the mean residence half-time of ¹³⁷Cs from global fallout in each soil layer was evaluated with a compartment model. These values ranged from 1.0 to 6.3 years/cm. The mean residence half-time averaged over all soil layers and all sites was 2.7±1.4 years/cm and, thus, about twice the corresponding residence half-time of the Chernobyl-derived ¹³⁷Cs as determined in the same soil layers (also in 1993). The dose rate of the external gamma-radiation due to ¹³⁷Cs from global fallout in the soil determined from the depth distributions varied between 0.34 and 0.57 (mean: 0.45±0.07) nGy/h per kBq/m². The effect of soil water content on the dose rate was studied by considering four states of the soil, from water content zero to complete water saturation of the total pore volume. It was shown that the difference between the dose rates at the permanent wilting point and the field capacity, which both represent the most relevant water contents of soils, was only 10% of the dose rate at the permanent wilting point for all sites. Received: 8 September 1997 / Accepted in revised form: 15 December 1997     

Dynamic study of the cytogenetic effects in blood lymphocytes from humans living in the Chernobyl Atomic Energy Station exclusion zone without permission

The cytogenetic examination of a group of people, self-residing in ChNPP Exclusion Zone with soil contamination density 137Cs 74-477 kBq/m2, 90Sr 33-289 kBq/m2, 238, 239 + 240Pu 1.5-10.0 kBq/m2, was conducted in 1998-1999 and also 2001. It is shown, that after 12-15 years of the accident the level of chromosome damages in Zone self-residents' lymphocytes detected by a routine analysis is higher then at the residents of control Yagotin district, Kiev region and comes to a plateau. Lymphocytes with multiple chromosome damages are detected. The probability of its transuranium elements induction which are present in the Zone is discussed at present.     

Fallout radiocesium in an Antarctic region:

To improve the knowledge about the (137)Cs spatial distribution and vertical migration in soils of the Southern Hemisphere, the total areal activity density and the vertical transport parameters of this radionuclide were measured in an Antarctic region. For this purpose vegetation and incremental soil samples were collected at 21 representative sites located at 4 islands of the South Shetland Archipelago: King George, Robert, Greenwich and Snow (62-63 degrees S and 58-62 degrees W). The total (137)Cs activity density varied considerably from 118 to 662 Bq m(-2) (median 384 Bq m(-2), reference date 1995), with a high percentage of the total activity retained in the vegetation cover (5-98% in moss, 3-20% in lichen and 4-12% in grass). At most sites, the maximum activity density in soil was observed in the top layer from where it decreased continuously. To evaluate the transport parameters of (137)Cs from the activity-depth profiles, the classical convection-diffusion model was used based on the time-course of the annual deposition density of (137)Cs at the studied region. The values for the diffusion coefficient D(s) (median 0.043 cm(2) year(-1)) and the convection velocity v(s) (median -0.012 cm year(-1)) of radiocesium observed under a polar climate are small compared to the transport parameters determined in temperate zones. The data also indicate that at these sites the convectional transport of (137)Cs is almost negligible compared to the transport by diffusion. The high vulnerability of the Antarctic soils to (137)Cs deposition, as a consequence of its very slow transport due to the extreme climatic conditions at these latitudes, has been confirmed.     

Internal and external sources of the radiation induce the blocking of the proliferation of the human endothelial cells in culture. G2-block is induced by beta-particle 3H-thymidine and gamma-rays 137Cs

We found that low doses (0.12-0.46Gy) of (methyl-) 3H-thymidine incorporated into human endothelial cells induce the accumulation cells in G2-phase of the cell cycle. Temperate doses of (1-6 Gy) gamma-rays 137Cs were less effective in the G2-block estimated by flow cytometry analysis of DNA content. Furthermore, the induced the high level of the chromosome aberrations (bridges and fragments in anaphases). 1Gy of gamma-ray 137Cs and 0.005 Gy of beta-rays induced the same per cent of the aberrant anaphases. Apparently, that the damages of the cellular hereditary structures are responsible for the blocking of the cellular proliferation in G2-phase. We suggest, that the disposition 3H-thymidine into radiosensitive target (DNA) defines the high cytotoxic of the beta-rays.     

The analysis of coefficient of 137Cs transfer from soil into potato in relationship with 137Cs content in soil and plant mineral feed

The soil-potato transfer factor for 137Cs (TF) was estimated by using results of 137Cs activity concentration measurements in 214 samples of soil and potato taken at fields with various level of contamination with 137Cs. The relationships between the coefficient TF and soil characteristics (acidity pH (KCl), content of K2O, P2O5, CaO and MgO in soil) and soil contamination with 137Cs have been analysed. The results show that the TF values tend to decrease with increasing concentration of 137Cs, K2O, P2O5, and CaO in considered sod-podsolic sandyloam soil. The regression function describing the TF dependence of 137Cs, K2O, P2O5, and CaO content in soil has been derived.     

The transfer of 90Sr and of 137Cs radionuclides in the chain of soil-fodder-animal products in the area contaminated as a consequence of the Chernobyl AES accident

The database on 137Cs and or 90Sr transfer factors in the soil-fodder-animal products chain compiled in the framework of the project "Radioecological Consequences of the Chernobyl Accident" under the French-German Initiative was analyzed. The 137Cs transfer factors were determined into 10 fodder types for farm animals. The 137Cs and 90Sr transfer from daily diet to milk is practically independent from milk yield and season and is about 0.83% and 0.16%. 137Cs transfer factor into beef (adult animals) is about to 2.4% from the daily uptake with fodder per 1 kg meat.     

Short rotation coppice as alternative land use for Chernobyl-contaminated areas of Belarus

Field experiments were conducted in the Chernobyl-affected area to assess if short rotation coppice (SRC) for energy production is a feasible alternative for contaminated land. Four willow clones were planted on sandy and peaty soil and the radiocaesium (137Cs) and radiostrontium (90Sr) transfer factors (TF) and yield relevant parameters were recorded during four growing seasons. The 137Cs and 90Sr soil-to-willow wood TF on sandy soil (second growing season) were on average 1.40+/-1.06 x 10(-3) m2 kg(-1) and 130+/-74 x 10(-3) m2 kg(-1), respectively. The 137Cs TF recorded for the peaty soil (fourth growing season or end of the first rotation cycle) was on average 5.17+/-1.59 x 10(-3) m2 kg(-1). The 90Sr-TF was on average 2.61+/-0.44 x 10(-3) m2 kg(-1). No significant differences between clones for the 137Cs and 90Sr-TF were observed. Given the high TFs and the high deposition levels, Belarus exemption levels for fuel wood were highly exceeded. The annual average biomass production for one rotation cycle on the peaty soil ranged from 7.8 to 16.0 t ha(-1) y(-1) for one of the clones, comparable with average annual yield figures obtained for western Europe. On the sandy soils, first-year yields were 0.25 t ha(-1) y(-1). These soils are not suitable for SRC production and should better be dedicated to pine forests or drought-resistant grasses.     

The accumulation of the technogenic radionuclides by mushrooms in the area affected by the activity of the Krasnoyarsk mining-and-chemical industrial complex

The radionuclide content was measured in mushrooms collected in different sites situated in the zone of the radiation influence on the Mining-and-Chemical Combine at Zheleznogorsk and on the control site, near Krasnoyarsk, in 2002-2004. The analytical investigations of fruiting bodies of 12 mushroom species have revealed three gamma-emitting radionuclides: 7Be, 40K (natural) and 137Cs (artificial). It was found that only three species contain 7Be; activity concentration of 40K is not species- and site-dependent, averaging 1600 Bq/kg. All collected samples contain 137Cs, and its accumulation by mushrooms is species-specific. Suillus concentrates more 137Cs activity than other species and can be used as a bioindicator of soil contamination with radiocesium. The average activity concentration of 137Cs in Suillus granulatus collected in the sites subjected only to aerosol discharges of the MCC is more than twice higher than 137Cs content of the mushrooms collected in the control site--"Krasnoyarsk". The maximum activity concentration of 137Cs in Suillus samples collected in the sites that receive 137Cs with the flood water is an order of magnitude higher, amounting to 8624 Bq/kg. The analysis of the radionuclide distribution in a mushroom shows that 40K activity concentration is the same in caps and stems of Suillus, and 137Cs concentration in Suillus caps is 1.7-2.3 times higher than in stems. Binding of radionuclides by mushroom biomass was determined by chemical fractionation; it was found that the highest activities of 137Cs and 40K are in the exchange-adsorption fraction (56 to 71% of the total content of a radionuclide) and in the organic fraction (23 to 37%). Calculations were made for determination of the coefficients of 40K and 137Cs transfer from the soil to the fruiting body of Suillus.     

The features of radioactive contamination of small birds in Chernobyl zone in 2003-2005

Radioactive contamination of small birds (484 individuals, 44 species) was investigated in the Chernobyl zone (Ukraine) in 2003-2005. Values variation of 90Sr and of 137Cs activity concentration reached 3-4 orders of magnitude even in one site, and maximum values amounted to hundreds Bq/g at the central plots of the zone. The biggest contamination is appropriate to birds in breeding season and to settled species, whilst migrants are the "cleanest". Change of contamination within a year reflects seasonal and short-term changes in birds diet and in behaviour. During breeding season females have higher activity concentration of 90Sr, while on 137Cs accumulation sexual differences are absent. In other seasons radioactive contamination of male and female does not differ if they live in similar conditions and have similar migratory behavior. Young birds during fledging and just after, as a rule, have higher levels of 90Sr contamination than adults, and actually do not differ on 137Cs accumulation. On a set of own and published data, it was assumed, that in small birds the half-life period of 137Cs extraction amounts to 1-2 days, and 90Sr- 5-10 days, and dynamic equilibrium of the radionuclides turnover in organism is reached over 4-7 and 17-34 days, respectively, after the birds arrival on the contaminated site. Among 44 studied species, those who search invertebrates in soil top layer or forest litter (thrushes). have noticeably higher accumulation of 90Sr and of 137Cs. Specific differences of radionuclides accumulation for the rest birds were not revealed due to small sample sizes of the species.     

Cytogenetic effect in peripheral blood lymphocytes of children living in villages in the Ovruch District, Zhitomir Region of the Ukraine contaminated by radionuclides]

For the purpose of genetic indication of low level of chronic radiation exposure the cytogenetic monitoring of some critical children groups living in two contaminated Ukrainian villages was carried out. In all the groups the mean frequency of aberrant cells and chromosome type aberrations (including dicentrics, centric rings, chromosome translocations as well as polyploid cells) significantly exceeded control level. During the repeated examination of children from Vistupovichi (in 13 months after the first one) the striking increase of cytogenetic effect was revealed. Dicentrics and rings were registered in 79% of persons with the individual rate 0.5-1.5 and mean group frequency 0.57 per 100 cells. The authors tried to evaluate the average cumulative doses of radiation for examined groups using G. Littlefield equation for dicentric outcome under the low dose rate Cs-137 source and taking into account the assumption about the reducing of 50% dicentrics per year. According to this rough calculation, the revealed cytogenetic effect can correspond to the mean total dose of 33 cSv for Vistupovichi children.     

The cytogenetic and hematotoxic effect of cesium-137 incorporated in the rat body]

The influence of incorporated 137Cs on peripheral blood cells was studied at different times after a single per os administration to rats. Moderate lymphopenia occurred in 26 days. A 30-70% increase in the number of aberrant lymphocytes was revealed throughout the entire period of observation (up to 547 days). Rats are suggested to develop a pronounced immune depression and chronic radiation sickness.     

137Cs vertical migration in boggy soils in the long term after the Chernobyl accident

137Cs vertical migration in boggy soils has been studied 15 years after the Chernobyl accident. The rate of vertical migration of the radionuclide is shown to be dependent on the peculiarities of formation of peatbogs, their moistening regime and soil properties. 137Cs migration in a high-land peatbog is characterized by higher intensity then in lowland or transitional peatbogs. Differences in 137Cs vertical migration are to a large extent caused by the contents in soil of exhangeable and mobile radionuclide forms. The derived experimental data that describe 137Cs distribution over the profiles of peaty soils of different type are used for parameterization of two-component convective-diffusion model. Ecological and effective half-life periods of 137Cs content reduction in the soil root layer have been calculated. A long-term prediction is given of the dynamics of the radionuclide content in the root layer of peaty soils.     

Iodine-129 measurements in soil samples from Dolon village near the Semipalatinsk nuclear test site

Dolon village, located about 60 km from the border of the Semipalatinsk nuclear test site, is known to be heavily contaminated by the first USSR atomic bomb test in August 1949. Soil samples around Dolon were taken in October 2005 in an attempt to evaluate internal thyroid dose arising from incorporation of radioiodine isotopes (mainly (131)I). Iodine-129 in soil was measured by using the technique of accelerator mass spectrometry. The (129)I/(127)I atom ratios measured were in the range from 3.3 x 10(-9) to 3.3 x 10(-7). These values were within the range of the current background level ( approximately 10(-9) to 10(-7)) in the environment, including contributions from the global fallout of atmospheric nuclear tests and local fallout of nuclear facilities. The (129)I atom accumulated level in soil ranged from 1.28 x 10(13) to 1.59 x 10(14) atoms m(-2), the average (8.0 x 10(13)) of which was higher than the background level of (2-5) x 10(13). From the relationship between (129)I and( 137)Cs (corrected for background and decay from 1949 to 2005) accumulated levels, the background level of (129)I and the (129)I/(137)Cs ratio around Dolon were estimated to be (6.4 +/- 0.4) x 10(13) atoms m(-2) and 0.25 +/- 0.16, respectively. This (129)I/(137)Cs ratio is almost similar to the fission yield ratio for (239)Pu fast fission (0.24).     

Effect of biotite,zeolite, heavy clay,bentonite and apatite on the uptake of radiocesium by grass from peat soil

Biotite is a potassium rich mineral, which is used as a fertilizer in organic farming and as a soil amendment in conventional farming. Its ability to reduce ¹³⁴Cs uptake by ryegrass from peat soil was studied in pot experiments and compared with zeolite, heavy clay, bentonite and apatite. In addition, the long-term effect of biotite on ¹³⁷Cs uptake from peat soil was studied in the peat field. In the pot experiments in the first cut of ryegrass, the minerals decreased ¹³⁴Cs uptake by plants in the following order: zeolite > heavy clay > bentonite > biotite > apatite. Apatite did not have any effect on the plant ¹³⁴Cs level. In the later cuts, the uptake of ¹³⁴Cs from biotite-treated soil decreased further while that from soils treated with other minerals remained unchanged or even increased. In general, ¹³⁴Cs uptake by plants decreased with increasing mineral level. The decrease of ¹³⁴Cs uptake became more efficient, especially at the early growth stage, by mixing small amounts of zeolite in biotite. The results of the field experiment indicated the long-term effect of biotite on reducing ¹³⁴Cs uptake by plants. Biotite application rate was 30 t ha-1. The five-year mean of the plant/soil concentration ratio of ¹³⁷Cs was 0.05 for biotite-treated soil, in contrast to 0.14 for the control soil. On the whole, biotite reduced considerably the ¹³⁷Cs level of plants on peat soil and this effect was long-lasting. For an effective reduction of plant radiocesium a great quantity of biotite is needed and therefore it is most suitable for greenhouse cultivation where contaminated slightly decomposed peat is used as a growing medium.