Traces of Chernobyl remain in reindeer

“It is mainly the northern herding districts of Jämtland County and the southern districts in Västerbotten County that need to take measures to make sure that reindeer to be slaughtered are below the accepted limit for radiocaesium”, says Professor Birgitta Åhman at SLU.

Countermeasures involve early slaughter in autumn, before the reindeer change to the winter diet, which usually contains a large proportion of ground lichens, and feeding reindeer “clean” feed a couple of weeks before slaughter.

Initially a rapid decline
In April 1986, one of the reactors at Chernobyl nuclear power plant exploded.
“During the first years the caesium content in reindeer rapidly declined. Today the decline is much slower”, says Birgitta Åhman.

An explanation is that the year-to-year decline in reindeer initially followed the decline in Reindeer lichens, the dominating source of caesium intake at the time. Over time, the decline in reindeer has levelled off. The explanation is that, as the levels in lichens have declined other parts of the vegetation have become more important, and that these plants contain radiocaesium that is still circulating between soil and vegetation.

Caesium in reindeer, an old problem
Cesium-137 does not occur naturally in nature, but is created through nuclear fission processes in nuclear power plants or in nuclear bomb explosions. As early as in the late 1950s, researchers measured relatively high levels of cesium-137 among reindeer in Norway – originating from nuclear weapons tests, which resulted in radioactive material being released high up in the atmosphere.

The first scientific articles on elevated caesium levels in reindeer and Sami people in Sweden were published in 1961. At that time, the radiocaesium content in reindeer meat reached 1000 Bq/kg. Prior to the Chernobyl accident the levels had declined to 200–300 Bq/kg.

“After the Chernobyl accident the mean value at some slaughters could be 40 000 Bq 137Cs per kg meat. The first year after the accident the food safety level for caesium was 300 Bq/kg and most of the produced meat was discarded. The safety level was later raised to 1500 Bq/kg, and today less than 100 out of the 50 000–75 000 yearly slaughtered reindeer are discarded”, says Birgitta Åhman.