ESR dosimetry study on population of settlements nearby Ust-Kamenogorsk city, Kazakhstan

The method of electron spin resonance (ESR) dosimetry has been applied to human tooth enamel, to obtain individual absorbed doses of residents of settlements in vicinity of Ust-Kamenogorsk city, Kazakhstan (located about 400 km to the east from the epicenter of explosion at the Semipalatinsk Nuclear Test Site, SNTS). This region developed as a major mining and metallurgical center during the Soviet period (uranium production). Most of the investigated settlements (Ust-Kamenogorsk city, Glubokoe, Tavriya, Gagarino) are located near the central axis of the radioactive fallout trace that originated from the surface nuclear test on 24 August 1956, while the Kokpekty settlement (located 400 km to the Southeast from SNTS) was chosen as a control because it was not subjected to any radioactive contamination. In total, 44 samples were measured. It was found that the excess doses obtained after subtraction of natural background radiation ranged up to about 114 mGy for residents of Ust-Kamenogorsk city, whose tooth enamel was formed before 1956. For residents of Gagarino, excess doses did not exceed 47 mGy for all ages. For residents of Tavriya, the maximum excess dose was 54 mGy, while for residents of Glubokoe it was about 58 mGy. For the population of the Shemonaikha settlements located at a distance of about 70 km from the central axis of the radioactive fallout trace, highest excess doses were 110 mGy. These high doses may be due to the influence of uranium enterprises located in that region, but probably not due to dental X-ray irradiation. For a final conclusion on the radiological situation in this region, the number of samples was too small and, therefore, more work is required to obtain representative results.     

Association tests in nuclear families

We present a conditional likelihood approach for testing linkage disequilibrium in nuclear families having multiple affected offspring. The likelihood, conditioned on the identity-by-descent (IBD) structure of the sibling genotypes, is unaffected by familial correlation in disease status that arises from linkage between a marker locus and the unobserved trait locus. Two such conditional likelihoods are compared: one that conditions on IBD and phase of the transmitted alleles and a second which conditions only on IBD of the transmitted alleles. Under the log-additive model, the first likelihood is equivalent to the allele-counting methods proposed in the literature. The second likelihood is valid under the added assumption of equal male and female recombination fractions. In a simulation study, we demonstrated that in sibships having two or three affected siblings the score test from each likelihood had the correct test size for testing disequilibrium. They also led to equivalent power to detect linkage disequilibrium at the 5% significance level.     

Sex ratio in the offspring of parents with chronic radiation exposure from nuclear testing in Kazakhstan

The former Soviet Union conducted a nuclear test program in the Semipalatinsk region of northeastern Kazakhstan in 1949-1989. The population in the vicinity of the test site was chronically exposed to radiation fallout, especially from above-ground tests during 1949-1956. Male:female sex ratio has been proposed as a measure of reproductive health, with some reports suggesting an alteration in the sex ratio of offspring of parents exposed to radiation. We investigated the impact of radiation exposure and other factors on the sex ratio in the population inhabiting the exposed region. A total of 11,464 singleton births of 3,992 mothers exposed to radiation during 1949-1956 were analyzed. The overall sex ratio was 1.07, similar to the current sex ratio in Kazakhstan (1.06). The sex ratio increased from 1.04 where mothers received <20.0 cSv to 1.12 where mothers received > or =60.0 cSv. However, the linear trend across exposures was not significant (P = 0.42). No consistent association was found between the sex ratio and the time since parental radiation exposure, parental age at exposure, or year of birth. Sex ratio was significantly associated with maternal age, birth order and possibly ethnicity but not with paternal age, parental educational level or season. In conclusion, no significant association was found between radiation exposure level and sex ratio, but some previously suggested demographic factors were positively associated with sex ratio.     

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.     

Genetic diversity in three perennial grasses from the Semipalatinsk nuclear testing region of Kazakhstan after long-term radiation exposure

The extent and structure of the genetic diversity of plant populations from the Semipalatinsk region of Kazakhstan, adjacent to a former major nuclear test site, have been studied using RAPD (Random Amplified Polymorphic DNA) marker analyses. The DNAs from three perennial species, Stipa capillata, Hordeum bogdanii, and Agropyron pectinatum, each collected from heavily (HPZ), moderately (MPZ) and lightly polluted zones (LPZ) have been analyzed using RAPDs. The results show a significantly higher level of variability in plants collected from the highest radiation pollution area compared with the moderately and lightly radiation contaminated zones for A. pectinatum and H. bogdanii. Variation was five times as higher in heavily exposed H. bogdanii, and two times higher in A. pectinatum populations compared to their lightly contaminated populations. H. bogdanii appears to be very sensitive to radiation and as such is a good indicator species for mapping radiation pollution at nuclear test sites or nuclear accidents.     

Fallout from the Chernobyl accident and overall cancer incidence in Finland

Aim: We studied whether incidence of all cancer sites combined was associated with the radiation exposure due to fallout from the Chernobyl accident in Finland. An emphasis was on the first decade after the accident to assess the suggested “promotion effect”. Methods: The segment of Finnish population with a stable residence in the first post-Chernobyl year (2 million people) was studied. The analyses were based on a 250 m × 250 m grid squares covering all of Finland and all cancer cases except cancers of the breast, prostate and lung. Cancer incidence in four exposure areas (based on first-year dose due to external exposure <0.1 mSv, 0.1–1.3, 0.3–0.5, or ≥0.5 mSv) was compared before the Chernobyl accident (1981–1985) and after it (1988–2007) taking into account cancer incidence trends for a longer period prior to the accident (since 1966). Results: There were no systematic differences in the cancer incidence in relation to radiation exposure in any calendar period, or any subgroup by sex or age at accident. Conclusion: The current large and comprehensive cohort analysis of the relatively low levels of the Chernobyl fallout in Finland did not observe a cancer promotion effect.     

Dendroclimatology in Kazakhstan

We have reviewed 43 studies related to dendroclimatology in Kazakhstan, and additionally 13 studies related to other subfields of dendrochronology, which have been published during the past 40 years. This review also includes studies published in Russian, Kazakh, German and Chinese languages, which are not easily accessible to international researchers.Dendroclimatic studies in Kazakhstan began back in the days of the Soviet Union and were actively conducted in the southern and northern parts of the country. With the collapse of the Soviet Union dendroclimatic studies stopped and resumed only 15-20 years later. Within the last 5 years, the intensity and quality of dendroclimatic studies increased significantly. Several research groups have investigated climate-growth relationships of Scots pine, Silver birch, Siberian larch, Siever’s apple and Schrenk spruce. Schrenk spruce was the most widely studied of these species, and several climatic reconstructions have been published based off their climate-growth relationships. Results of most studies on Schrenk spruce demonstrated good consistency, allowing the general patterns of climate-growth relationships to be accurately traced. Unfortunately, studies on other tree species have either lower level or represented just by one or two studies. It would therefore be premature to make any generalizations on these species at the current stage.We conclude that there is a good potential and good base for continuing dendroclimatic studies in Kazakhstan. There is a need to close several research gaps which limit our knowledge, such as chronologies’ length, application of new methods, species composition and spatial coverage. Closing these gaps let us significantly improve the dendrochronological network of Kazakhstan and provide important data for further hydrological and climate studies in Kazakhstan.