Increased sex ratio in Russia and Cuba after Chernobyl: a radiological hypothesis.

BACKGROUND: The ratio of male to female offspring at birth may be a simple and non-invasive way to monitor the reproductive health of a population. Except in societies where selective abortion skews the sex ratio, approximately 105 boys are born for every 100 girls. Generally, the human sex ratio at birth is remarkably constant in large populations. After the Chernobyl nuclear power plant accident in April 1986, a long lasting significant elevation in the sex ratio has been found in Russia, i.e. more boys or fewer girls compared to expectation were born. Recently, also for Cuba an escalated sex ratio from 1987 onward has been documented and discussed in the scientific literature. PRESENTATION OF THE HYPOTHESIS: By the end of the eighties of the last century in Cuba as much as about 60% of the food imports were provided by the former Soviet Union. Due to its difficult economic situation, Cuba had neither the necessary insight nor the political strength to circumvent the detrimental genetic effects of imported radioactively contaminated foodstuffs after Chernobyl. We propose that the long term stable sex ratio increase in Cuba is essentially due to ionizing radiation. TESTING OF THE HYPOTHESIS: A synoptic trend analysis of Russian and Cuban annual sex ratios discloses upward jumps in 1987. The estimated jump height from 1986 to 1987 in Russia measures 0.51% with a 95% confidence interval (0.28, 0.75), p value < 0.0001. In Cuba the estimated jump height measures 2.99% (2.39, 3.60), p value < 0.0001. The hypothesis may be tested by reconstruction of imports from the world markets to Cuba and by radiological analyses of remains in Cuba for Cs-137 and Sr-90. IMPLICATIONS OF THE HYPOTHESIS: If the evidence for the hypothesis is strengthened, there is potential to learn about genetic radiation risks and to prevent similar effects in present and future exposure situations.

Artificial and natural radioactivity in edible mushrooms from Sao Paulo, Brazil.

Environmental biomonitoring has demonstrated that organisms such as crustaceans, fish and mushrooms are useful to evaluate and monitor both ecosystem contamination and quality. Particularly, some mushroom species have a high capacity to retain radionuclides and some toxic elements from the soil and the air. The potential of mushrooms to accumulate radionuclides in their fruit-bodies has been well documented. However, there are no studies that determine natural and artificial radionuclide composition in edible mushrooms, in Brazil. Artificial ((137)Cs) and natural radioactivity ((40)K, (22)(6)Ra, (2)(28)Ra) were determined in 17 mushroom samples from 3 commercialized edible mushroom species. The edible mushrooms collected were Agaricus sp., Pleurotus sp. and Lentinula sp. species. The activity measurements were carried out by gamma spectrometry. The levels of (137)Cs varied from 1.45 ± 0.04 to 10.6 ± 0.3 Bq kg(-1), (40)K levels varied from 461 ± 2 to 1535 ± 10 Bq kg(-1), (2)(26)Ra levels varied from 14 ± 3 to 66 ± 12 Bq kg(-1) and (228)Ra levels varied from 6.2 ± 0.2 to 54.2 ± 1.7 Bq kg(-1). (137)Cs levels in Brazilian mushrooms are in accordance with the radioactive fallout in the Southern Hemisphere. The artificial and natural activities determined in this study were found to be below the maximum permissible levels as established by national legislation. Thus, these mushroom species can be normally consumed by the population without any apparent risks to human health.

Variability of 137Cs and 40K soil-to-fruit transfer factor in tropical lemon trees during the fruit development period.

In this investigation we evaluate the soil uptake of (137)Cs and (40)K by tropical plants and their consequent translocation to fruits, by calculating the soil-to-fruit transfer factors defined as F(v) = [concentration of radionuclide in fruit (Bq kg(-1) dry mass)/concentration of radionuclide in soil (Bq kg(-1) dry mass in upper 20 cm)]. In order to obtain F(v) values, the accumulation of these radionuclides in fruits of lemon trees (Citrus limon B.) during the fruit growth was measured. A mathematical model was calibrated from the experimental data allowing simulating the incorporation process of these radionuclides by fruits. Although the fruit incorporates a lot more potassium than cesium, both radionuclides present similar absorption patterns during the entire growth period. F(v) ranged from 0.54 to 1.02 for (40)K and from 0.02 to 0.06 for (137)Cs. Maximum F(v) values are reached at the initial time of fruit growth and decrease as the fruit develops, being lowest at the maturation period. As a result of applying the model a decreasing exponential function is derived for F(v) as time increases. The agreement between the theoretical approach and the experimental values is satisfactory.

The effect of organic amendment on potential mobility and bioavailability of 137Cs and 60Co in tropical soils.

In this work the role of organic matter in the potential mobility and bioavailability of 137Cs and 60Co in Brazilian soil was investigated. Radish was cultivated in pots containing the top layer (0-20 cm) of a Histosol, Ferralsol and Nitisol spiked with 137Cs and 60Co. In the case of the Ferralsol and Nitisol samples, besides the control, two different rates of organic amendments were used. In these soils, a sequential extraction protocol was used to identify the main soil compartments that could be responsible for the variation of transfer factor values. Our results indicate that organic amendment could be suggested as a practical countermeasure for 137Cs and 60Co contamination, since it reduces bioavailability of radionuclides and, consequently, soil to plant transfer factor values by almost one order of magnitude in a short period of time.

Soil to plant transfer of 137Cs and 60Co in Ferralsol, Nitisol and Acrisol.

In this study, soil to plant transfer factor values were determined for 137Cs and 60Co in radish (Raphanus sativus), maize (Zea mays L.) and cabbage (Brassica oleracea L. var. capitata) growing in gibbsite-, kaolinite- and iron-oxide-rich soils. After 3 years of experiment in lysimeters it was possible to identify the main soil properties able to modify the soil to plant transfer processes, e.g. exchangeable K and pH, for 137Cs, and organic matter for 60Co. Results of sequential chemical extraction were coherent with root uptake and allowed the recognition of the role of iron oxides on 137Cs behaviour and of Mn oxides on 60Co behaviour. This information should provide support for adequate choices of countermeasures to be applied on tropical soils in case of accident or for remediation purposes.

Accumulation of (137)Cs in Brazilian soils and its transfer to plants under different climatic conditions.

The spatial distribution and behaviour of the global fallout (137)Cs in the tropical, subtropical and equatorial soil-plant systems were investigated at several upland sites in Brazil selected according to their climate characteristics, and to the agricultural importance. To determine the (137)Cs deposition density, undisturbed soil profiles were taken from 23 environments situated between the latitudes of 02 degrees N and 30 degrees S. Sampling sites located along to the equator exhibited (137)Cs deposition densities with an average value of 219Bqm(-2). Extremely low deposition densities of 1.3Bqm(-2) were found in the Amazon region. In contrast, the southern part of Brazil, located between latitudes of 20 degrees S and 34 degrees S, exhibited considerably higher deposition densities ranging from 140Bqm(-2) to 1620Bqm(-2). To examine the (137)Cs soil-to-plant transfer in the Brazilian agricultural products, 29 mainly tropical plant species, and corresponding soil samples were collected at 43 sampling locations in nine federal states of Brazil. Values of the (137)Cs concentration factor plant/soil exhibited a large range from 0.020 (beans) to 6.2 (cassava). Samples of some plant species originated from different collecting areas showed different concentration factors. The (137)Cs content of some plants collected was not measurable due to a very low (137)Cs concentration level found in the upper layers of the incremental soils. Globally, the soil-to-plant transfer of (137)Cs can be described by a logarithmic normal distribution with a geometric mean of 0.3 and a geometric standard deviation of 3.9.

Radioactive and stable metal bioaccumulation, crystalline compound and siderophore detection in Clavariadelphus truncatus.

137Cs and 40K activity concentrations and stable elements have been measured in Clavariadelphus truncatus collected in Mexico. Iron-chelating compounds of siderophore-type was also studied in the species. 137Cs and 40K were determined in soil and mushroom samples with HpGe gamma-ray spectrometry. Macro- and micro-elemental concentrations were determined by XRF and ICP-MS. Siderophore detection was obtained with a colorimetric assay and X-ray diffraction analysis was performed using a Siemens D5000 diffractometer. 137Cs geometric mean concentration in C. truncatus was 26 times higher as compared with other Mexican edible mushroom species, while 40K showed stability. Soil-C. truncatus concentration ratio for 137Cs and other micro-elements such as Cs, Rb and Pb were also higher than other Mexican edible species. The 137Cs committed effective dose due to the ingestion of C. truncatus was 8 x 10(-6) Sv year(-1). The main crystalline structure found in C. truncatus was D-Mannitol.

Radiocesium contamination behavior and its effect on potassium absorption in tropical or subtropical plants.

The accumulation and long-term decline of radiocesium contamination in tropical plant species was studied through measurements of gamma-ray spectra from pomegranate (Punica granatum) and chili pepper (Capsicum fructescens) trees. The plants were originally grown at a (137)Cs contaminated site (where a radiological accident occurred in the city of Goiânia, Brazil, in 1987), and transplanted to uncontaminated soil, so that the main source of contamination of the new leaves and fruits would be the fraction of the available radiocesium in the body of the plants. Measurements of (137)Cs and (40)K concentrations along the roots, main trunk, twigs, leaves and fruits before and after the transplant process of both plant species indicated a direct competition between Cs and K ions, suggesting that these elements could have a common accumulation mechanism. Cesium transfer factors from soil to pomegranate, green and red chili pepper fruits were evaluated as 0.4 +/- 0.1, 0.06 +/- 0.01 and 0.05 +/- 0.01, respectively. Biological half-life values due to (137)Cs translocation from the tree reservoir (BHL(T)) were calculated as 0.30 years for pomegranate, 0.12 years and 0.07 years for red and green peppers, respectively.

137Cs and relationships with major and trace elements in edible mushrooms from Mexico.

137Cs and 40K specific activity together with major and trace elements were determined in soil samples and in different edible wild mushroom species collected from a seminatural temperate forest ecosystem located in the central part of the Mexican Volcanic Belt. The activity measurements were made using a gamma-ray spectrometer system with a high purity germanium (HpGe) detector. The major and trace elements were determined using emission spectrography and mass spectrometry, respectively. The aggregated transfer factors for 137Cs were estimated in 30 local mushroom species collected from 1993 to 1999. Differences as large as three orders of magnitude were observed. The contribution of mushrooms for the total 137Cs dietary intake by the local population was estimated to be 37%. Mushrooms also showed to be good accumulators for Rb, Cu, Cs and Se.

Bioaccumulation of 137Cs and 60Co by a tropical marine teleost Epinephelus sp.

As part of a project on the behaviour of radionuclides released by the Angra Nuclear Power Station in the marine environment, laboratory experiments were performed to study cesium and cobalt accumulation by juvenile groupers (Epinephelus sp.). The fishes were kept in aquariums equipped with gravel-bed filters spiked with 60Co (150 KBq/l) and 137Cs (75 KBq/l). Uptake was only via water since the fishes received only non-radioactive food during the 4 months of experiment. Cesium accumulation in muscle was higher than in any other organ, reaching concentration factors (CFs) of 5 (fresh weight basis). Cobalt, in contrast, was concentrated mostly in the liver, gut and skin and scales. Cobalt CF in muscle tissue was 8 x 10(-2), lower than any previously reported figure. Chromatographic analysis of the water at the beginning and end of the experiment showed that cobalt had been completely converted from 60CoCl2 to non-cationic forms, most probably through complexation with organic ligands, mediated by the intense microbial activity of the filter bed. This conversion apparently enhanced cobalt bioavailability since a second experiment performed with this aged seawater yielded CFs for muscle tissue higher by a factor of 2.5.

Incorporaçäo e eliminaçäo de césio-134 pelo caramujo Biomphalaria glabrata (Say, 1818) / Uptake and loss of cessium-134 by the snail Biomphalaria glabrata (Say, 1818)

A incorporaçiao e eliminaçäo de Cs-134, produzido no reator IEA-R1 do IPEN, foram observadas em caramujos adultos de água doce. Duas atividades de Cs-134 foram empregadas: 3.700 e 18.500 Bq/1. As contagens foram feitas em um analisador monocanal e foram registrados o número de desovas e de embriöes. O máximo de incorporaçäo do radioisótopo ocorreu por volta de 8§ dia e a meia-vida biológica foi de aproximadamente 6 dias. Apesar do número total de desovas e de embrioes terem sido menores na presença de Césio-134, isto näo pode ser afirmado em virtude da pequena amostragem utilizada