Accumulation of 137cesium and 90strontium From Abiotic and Biotic Sources in Rodents at Chornobyl, Ukraine

Abstract

Bank voles (Clethrionomys glareolus) and laboratory strains of house mice (Mus musculus BALB and C57BL) were relocated into enclosures in a highly contaminated area of the Red Forest near the Chornobyl (Ukraine) Reactor 4 to evaluate the uptake rates of 137Cs and 90Sr from abiotic sources. Mice were provided with uncontaminated food supplies, ensuring that uptake of radionuclides was through soil ingestion, inhalation, or water. Mice were sampled before introduction and were reanalyzed every 10 d for 137Cs uptake. Levels of 90Sr were assessed in subsamples from the native populations and in experimental animals at the termination of the study. Uptake rates in house mice were greater than those in voles for both 137Cs and 90Sr. Daily uptake rates in house mice were estimated at 2.72 x 10(12) unstable atoms per gram (whole body) for 137Cs and 4.04 x 10(10) unstable atoms per gram for 90Sr. Comparable rates in voles were 2.26 x 10(11) unstable atoms per gram for 137Cs and 1.94 x 10(10) unstable atoms per gram for 90Sr. By comparing values from voles in the enclosures to those from wild voles caught within 50 m of the enclosures, it was estimated that only 8.5% of 137Cs was incorporated from abiotic sources, leaving 91.5% being incorporated by uptake from biotic materials. The fraction of 90Sr uptake from abiotic sources was at least 66.7% (and was probably much higher). Accumulated whole-body doses during the enclosure periods were estimated as 174 mGy from intramuscular 137Cs and 68 mGy by skeletal 90Sr in house mice over 40 d and 98 mGy from 137Cs and 19 mGy from 90Sr in voles over 30 d. Thus, uptake of radionuclides from abiotic materials in the Red Forest at Chornobyl is an important source of internal contamination.

Radiation Ecology Issues Associated With Murine Rodents and Shrews in the Chernobyl Exclusion Zone

“…Detailed studies on accumulation, distribution and excretion of radionuclides have been conducted for a long time, but primarily regarding agricultural and laboratory animals (Buldakov and Moskalev 1968; Aleksakhin 1982;Korneev and Sirotkin 1987;Moskalev 1989; Vandecasteele et al 1989), and, therefore, they are not fully applicable for extrapolation to wild species. There has been very little applicable information available on wild animals inhabiting the ChEZ (Kozlo et al 1998;Chesser et al 2000Chesser et al , 2001Gaychenko et al 2001;Oleksyk et al 2002; Ryabokon et al 2005; Taskaev et al 1990). In view of this, in 1998 -2010, the International Radioecology Laboratory (IRL) performed a wide range of studies on accumulation and metabolism of radionuclides, as well as on dose rates, in wild murine rodents and shrews under the actual conditions of the ChEZ.…”

Where the wild things are: influence of radiation on the distribution of four mammalian species within the Chernobyl Exclusion Zone

“…Several studies have shown that wildlife within the zone continue to accumulate substantial amounts of radionuclides (Chesser et al . ; Geras'kin et al . ); other research has uncovered a range of negative health impacts on wildlife, including sperm deformities and increases in mutation rates, morbidity, and mortality (Møller et al .…”

Subchronic exposure of BALB/c and C57BL/6 strains of Mus musculus to the radioactive environment of the Chornobyl, Ukraine exclusion zone

“…The number of unstable atoms of 137 Cs is expected to approach a constant (i.e., asymptotic) value with time. Therefore, the asymptotic value for the number of unstable atoms of 137 Cs per gram of tissue was calculated according to the method described by Chesser et al [16]. The uptake rate, representing the daily loss rate by physical decay and biological processes, was also calculated for each strain.…”

“…Specific activities and concentrations in soil samples from the enclosures were 1,296 Bq g −1 (1.71 × 10 12 unstable atoms/g) for 90 Sr and 3,317 Bq g −1 (4.54 × 10 12 unstable atoms/g) for 137 Cs. Procedures necessary to determine uptake and accumulated dose rates in the enclosures are described in detail by Chesser et al [16] and include animals from this study. The primary interest for the present study was to calculate the dose caused by the uptake of radionuclides for the period after the mice were introduced into the enclosures and to relate that dose to MN induction.…”

“…Other voles common to the Chornobyl exclusion zone include species of Microtus , which have an LD50/30 of more than 10 Gy [15]. Therefore, native species, although valuable in documenting radionuclide accumulation and distribution of 90 Sr and 137 Cs in the exclusion zone [12, 16, 17], may not be the most appropriate indicator for the risk of human exposure to the Chornobyl environment. Few studies have explored the biological consequences of low‐dose, continual environmental radiation exposure in the Mus model system, even though the BALB/c (LD50/30 = 5.5 Gy) and C57BL/6 (LD50/30 = 6.0 Gy) strains of M. musculus demonstrate sensitivity to radiation [1, 3, 7] more similar to that of humans.…”