Radioactivity in Food and the Environment (RIFE 9) report: Your questions answered

Over the past 20 years or so, levels of man-made radionuclides in food have generally decreased reflecting decreases in authorised discharges of radioactive waste from nuclear sites.

Some exceptions include tritium [a radioactive form of hydrogen] in the waters around Cardiff due to discharges from a plant that makes chemicals for the medical industry. Tritium levels in fish have been much greater than expected within the last decade or so but show signs of coming down slowly. Tritium is not very damaging to the body and eating these fish and shellfish will only give small doses to consumers.

Levels of the radionuclide technetium-99 in shellfish around Sellafield went up rapidly in the late 1990s but are decreasing now. The increases were expected as technetium-99 discharges from Sellafield increased dramatically in 1997 when a new plant opened on site that reprocessed new types of nuclear fuel. Technetium-99, like tritium, is weakly radioactive so even relatively high levels in foods give low doses to consumers.

The report is free.

An electronic copy of RIFE 9 is available in pdf format. If you would prefer a hard copy of the report or a copy on CD containing the entire series of RIFE reports then you can email us at radiological.surveillance@foodstandards.gsi.gov.uk, Tel: 020 7276 8748 or send to RIFE team, Food Standards Agency, Floor 7, Aviation House, 125 Kingsway, London, WC2B 6NH. Let us know if you only want RIFE 9 or whether you would like to go on our distribution list for future versions of RIFE.

The report shows that in 2003, the exposure to members of the public to artificially produced radioactivity via the food chain was well below the dose limit.

The highest estimated radiological exposures were for a group of fish and shellfish consumers around Sellafield in Cumbria. They could receive up to 620 microsieverts [a measure of how much radiation the body absorbs] from radionuclides discharged into the Irish Sea. The EU dose limit is 1000 microsieverts. All other members of the UK will receive lower - mostly much lower - exposures due to eating food.

The vast majority of radionuclides in food are from natural sources. Radioactivity is always present in soil and in the air that we breathe. It can get into crops via their roots and leaves or it can land on grass eaten by cows and hence get into milk. Similarly it is in water and fish and shellfish can absorb it. The average UK diet gives an exposure of about 170 microsieverts whilst the average exposure from all natural sources (including radon) in the UK is about 2200 microsieverts.

Only a small fraction of radiological exposure comes from man-made sources, such as fallout from bomb tests, residues from the accident at Chernobyl in 1986, the nuclear industry, etc. The average member of the UK gets less than 15% of their dose from man-made sources and of that over 96% is from medical treatment e.g. radiotherapy. Authorised discharges from the nuclear industry account for less than 0.01% of the dose.

Some radionuclides, such as carbon-14, can come from either man-made or natural sources but they have the same effects on the body regardless of source. Different types of radionuclides can give different doses and this is taken into account when exposures are calculated.

The RIFE report collates the levels of radionuclides in food and environmental samples mainly from the vicinity of UK nuclear sites and explains the radiological doses that the UK population could receive from the release of authorised radioactive discharges from these sites.

The report is the 9th in the series but the 2nd to be a joint publication with all the UK agencies involved with radiological monitoring - the Environment Agency, Scottish Environment Protection Agency and the Environment and Heritage Service for Northern Ireland.