Radiocaesium activity concentrations in sheep from restricted areas in England and Wales

Last updated:
19 January 2015
This project assessed radiocaesium levels in sheep within the restricted areas of Cumbria and North Wales as part of the post-Chernobyl monitoring programme
Study duration: November 2009 to November 2011
Project code: FS131011
Contractor: Food Standards Agency and RITE Advice Limited

Background

The Food Standards Agency (FSA) manages restrictions on the movement, sale and slaughter of sheep on farms in North Wales and in Cumbria, which remain affected by radiocaesium fallout from the Chernobyl accident. The restrictions are enforced using powers under the Food and Environment Protection Act (FEPA) 1985. A live sheep monitoring programme, known as ‘Mark and Release’, operates to ensure that sheep exceeding 1,000 Bq/kg of radiocaesium do not enter the food chain.

The aim of this project is to assess the levels of radiocaesium in sheep within the restricted areas and the potential consumer doses if control measures were to be lifted. The assessment will form the evidence base for a public consultation on a policy change in November 2011.

Research Approach

Sheep on restricted farms are to be monitored during the summers of 2010 and 2011 when radiocaesium activity concentrations are at their peak. A probabilistic dose model will be developed using the monitoring data to estimate the distribution of annual effective dose in millisieverts per year (mSv/y) to a Representative Person. The Representative Person corresponds to a more highly exposed consumer of sheep meat from a restricted farm, whose habits are realistic of what people encounter in their day to day life. A dose to the Representative Person will be calculated for each monitored farm, to give a range of doses representative of all restricted farms. Doses to consumers with different characteristics will also be modelled to demonstrate a robust understanding of doses if control measures were to be removed.

Doses will be compared to EU limits and guidance levels from the International Commission on Radiological Protection (ICRP). Whether Mark and Release control measures still reduce consumer doses will also be assessed.

Results

Low levels of radiocaesium persist in sheep throughout much of the restricted areas of Cumbria and North Wales, although consumer risks are considered to be very low.

Doses to the representative person range from <0.05mSv to 0.21mSv per year with a mean of <0.09mSv per year. These are considerably below the 1mSv per year limit established under Article 48 of Council Directive 96/29/Euratom for members of the public exposed to radiation from routine planned exposures and the 1mSv per year reference level typically used in existing exposure situations.

The maximum observed radiocaesium activity concentration in sheep did not exceed 1,000 Bq/kg on over 97% of monitored farms in North Wales. On the small number of Welsh farms where sheep have the potential to exceed 1,000 Bq/kg of radiocaesium, no more than 2.5% are ever likely to do so. Standard practice is to fatten sheep on improved pasture prior to slaughter, which would reduce radiocaesium levels to well below 1,000 Bq/kg in most cases.

Two farms monitored in Cumbria had a very small percentage of sheep that exceeded 1,000 Bq/kg of radiocaesium. As in North Wales, the standard practice of fattening of sheep on improved pasture ensures that very few sheep if any, exceeding 1,000 Bq/kg of radiocaesium, will enter the food chain in Cumbria. No sheep in Cumbria has failed the Mark and Release monitoring criterion in recent years.

The 1,000 Bq/kg criterion enforced by the Mark and Release programme is equivalent to permitting a dose of 0.26 mSv per year to the Representative Person. The highest modelled dose to the Representative Person was 0.21 mSv per year. Monitoring against the 1,000 Bq/kg limit is therefore having a negligible impact on reducing consumer doses.

The level of consumer risk, if control measures were to be removed, is significantly less than the level of risk tolerated by the existing policy. The Mark and Release monitoring programme is therefore having a negligible impact on reducing consumer risk.