Distribution of cesium-137 in reindeer

T h e influence of the C h e r n o b y l accident in 1986 o n the F i n n i s h reindeer herding area was much smaller than the effects of the nuclear b o m b tests in the 1960s. O n l y in one small area somewhat more Cs137 was deposited than in the rest of the reindeer herding area. F r o m that area 20 reindeer were chosen for investigation of the d is t r ibut ion of Cs-137. A l l tissues, organs, the skeleton, digestive tract, hide, head and hooves were sampled quantitat ively. Three reindeer were pregnant and also the foetuses were studied. T h e Cs137 amounts were determined by gammaspectrometric measurements. T h e results showed that the differences in the Cs-137 concentrations between muscle tissue f r o m different parts of an individual reindeer were not more than 10 percent. T h u s it is not essential f r o m w h i c h part of the reindeer meat samples for surveillance purposes are taken. T h e concentrat ion of Cs-137 in edible tissues other than muscle was lower except in the kidneys and scapula cartilage.


Introduction
The influence of the Chernobyl accident in 1986 on the Finnish reindeer herding area was much smaller than the effects of the nuclear bomb tests in the 1960s because of the northern situation and favourable winds at the time of the accident (Rahola and Miettinen 1977, Rissanen et al. 1987, Rissanen and Rahola, 1988and 1989).Only in the southeasternmost corner of the reindeer herding area was somewhat more Cs-137 deposited than in other parts of the reindeer herding area (Fig. 1, area V).But even here the amounts of radiocesium deposited were smaller than in the more southerly reindeer herding areas in Sweden and Norway.
The Cs-137 concentrations in reindeer meat have been followed closely since the accident on the whole reindeer herding area by taking samples from slaughtered reindeer.In Finland 130.000 -150.000reindeer are slaughtered each year, about 800 of these in area V (Fig. 1).Three of the reindeer were pregnant and two foetuses were big enough to enable sampling of their organs and tissues.The third reindeer was less than 1 year old; its foetus was very small and had to be measured undivided.

Material and methods
All samples were homogenized and some were dried before measurement.The gammaspectrometric measurements were performed with high purity lithium drifted germanium detectors and the results calculated as described in earlier publications (Rissanen et al, 1987).and Jaakkola, 1975, Rydberg, 1988).In Finland the neck is chosen since a sample taken from there does not reduce the market value of the carcase.
Cs-137 concentrations in edible tissues besides meat were lower, except in the kidneys and scapula cartilage.Fat did not contain Cs-137 and therefore the more fat in a tissue the lower the Cs-137 concentration.
The concentration in whole blood was about 10 per cent of that in meat.

Discussion
The differences in Cs-137 concentrations in muscle tissues from different parts of a single reindeer did not exceed 10 per cent.It is therefore not essential from which part of the animal samples for surveillance purposes are taken.
The same conclusions could be drawn also from earlier published investigations (Rahola Cs-137 Bq/kg Rangifer,2(10), 1990 These 800 reindeer did not create any radiation protection problem even in 1986, but were ideal for investigating the distribution of radio-cesium in reindeer.From the surveillance point of view Cs-137 concentrations in meat samples are the most important.Samples are taken from the neck of slaughtered reindeer in Finland but in Sweden from the shank.The aim of this study was to investigate differences in radiocesium concentrations between different muscles and in different organs and other tissues of the reindeer.
kept together and fed lichen containing 6000 -8000 Bq Cs-137/kg dry weight, similar to the lichen in their natural pasture.Under normal conditions these animals would have strayed to other areas of lower Cs-137 concentration in 1 Presented at the Sixth Nordic Workshop on Reindeer Research, Tromsø 8.-10.October 1990 Rangifer, 2 (10), 1990 57 the lichen.Therefore they had to be herded continously.The slaughtering was done in the open in temperatures of -10 to -35°C, and blood samples were also taken at that time.Carcase, all internal organs, digestive tract, hide, head and hooves were transported 400 km to the laboratory in Rovaniemi for further preparation.The meat of the carcasses were cut into sections (Fig.2).The skeleton was separated into individuals bones; the leg bones were further divided into diaphysis and epiphysis.Bone marrow and cartilage were sampled.All internal organs, including the whole digestive tract were sampled.Rumen contents was sampled qualitatively from the first five reindeer and quantitatively from the remainder.
Fig. 6 but in Bq/kg dry weight.The corresponding mean vaules and variations for all the 20 reindeer are given in Figures 8-11.The Cs-137 concentrations of the foetuses and mothers are presented in Table2.

Fig. 1 .
Fig. 1.Mean seasonal variation of Cs-137 concentrations in reindeer meat in region I-V of Finnish reindeer herding area, the indicator line shows minimum and maximum concentration.Results from June 1986 -February 1990.

Table 1 .
Time of slaughtering, number, sex, age and mean w r eight of the tw r enty reindeer studied.

Table 2 .
Cs-137 concentration, Bq/kg fresh weight, in reindeer and its foetus .The relation of Cs-concentration in their organs.