Chernobyl legacy lingers on ...

11 May 2000

Levels of radioactivity after the explosion of Chernobyl's reactor No 4 are still unexpectedly high - and will remain so for another fifty years - at least 100 times longer than anticipated, it is reported in Nature, out today.

"By looking at the levels of radioactivity of fish in lakes in Cumbria and Norway, we have found that levels of one particular element, radioactive caesium, are still unexpectedly high," says Dr Jim Smith, from the Centre of Ecology and Hydrology, team leader of the international research project.

"During the first five years after Chernobyl, concentrations of radioactive caesium in most foodstuffs and water decreased by a factor of ten, but in the last few years they have changed very little. The environment is not cleaning itself of the pollution at a rate we previously thought - in fact as time goes on after the explosion, it is taking longer for the levels of radioactivity to reduce.

"Whilst this contamination represents only a small health risk to consumers, it means that restrictions on foodstuffs, both in the UK and former Soviet Union, will need to remain in place for much longer than originally anticipated."

Generally, after a nuclear accident, ecosystems have a self-cleaning capacity - radioactive caesium becomes immobilised in the soil so that it becomes less easily accumulated by plants and animals. This 'fixation' process led to decreases in contamination of foodstuffs in the first few years after the accident. Now, fourteen years after Chernobyl, we have found that the radioactive caesium is not completely immobilised by the soil, but can be re-released to the ecosystem.

This is quite a different story to that expected. Before Chernobyl, most scientists believed that the soil immobilisation process was so strong that the contamination of foodstuffs would be relatively short-term. Ministry of Agriculture (MAFF) restrictions on the sale of sheep were expected to last only for a matter of weeks.

However, the reality is that lamb from more than 300 UK upland farms, as well as berries, mushrooms and fish from some areas of the former Soviet Union, are restricted for a while to come. Fish from some lakes, such as Lake Kozhanovskoe, in the former Soviet Union will remain under restriction for another fifty years.

Further information

Dr Jim Smith
CEH Dorset,
Winfrith Technology Centre,
Dorchester, DT2 8ZD.
Tel: 01305 213607
Fax: 01305 213600

NERC Press Office
Natural Environment Research Council
Polaris House, North Star Avenue
Swindon, SN2 1EU
Tel: 01793 411561
Mob: 07917 557215

Notes

1. The research team consists of Rob Comans from Netherlands Energy Research, Nick Beresford, Simon Wright and Brenda Howard from CEH Merlewood in Cumbria and Bill Camplin from the Centre for Environment, Fisheries and Aquaculture Science, Lowestoft.

2. Centre for Ecology and Hydrology (CEH), is a component institute of the Natural Environment Research Council (NERC). NERC is the leading body in the UK for research, survey, monitoring and training in the environmental sciences. NERC funds research in universities and in its own Centres and Surveys. NERC trains scientists for the future - more than 3,000 postgraduate students have been funded by NERC over the last five years.

Chernobyl legacy lingers on ...

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