Incident surveillance report: Radioactive Contaminated pigeons in Seascale village
13th March 1998
Background
On Friday 6 February MAFF was informed of contaminated feral pigeons in Seascale village, not far from the British Nuclear Fuels (BNFL) site at Sellafield in Cumbria. These birds were part of a group of about 700 birds that had been kept and fed at a pigeon sanctuary in Seascale. Some 150 of the birds had been humanely culled by the RSPCA (Royal Society for the Prevention of Cruelty to Animals), as part of a programme to reduce numbers, and a few taken to the Sellafield site for monitoring. The birds were suspected of roosting on the site.
Initial measurements undertaken by BNFL revealed significant levels of contamination on the pigeons taken from the sanctuary. Surface levels of radiation on the birds were reported to be as high as 1.4 millisieverts per hour (mSv/hr). At that stage it was unclear if it was only the birds' feathers that were contaminated or if there was also significant internal contamination of the birds.
The birds kept at the sanctuary were mainly feral pigeons, with a few lost racing pigeons, and as such are highly unlikely to have entered the human food chain.
MAFF asked BNFL to make available samples of pigeons taken to the site by the RSPCA (S group) and collected further pigeons stored by the RSPCA in Kendal ( K group). All these birds were obtained from the Seascale pigeon sanctuary. The birds were sent to the MAFF Veterinary Laboratory Agency (VLA) for analysis.
Results from provisional analysis of birds by BNFL, provided on 12 February, showed that there was significant internal contamination of up to 0.11 MBq.kg
-1, from which we calculated that the consumption of the breast meat from about 6 birds would give a radiation dose of 1 mSv, the annual public dose limit. Levels were also far in excess of EU Food Intervention Levels. The affected birds were feral pigeons, and a few lost racing pigeons, and so are unlikely to have been eaten. A survey of traders in the area confirmed there was no pigeon meat for sale. However, as a precaution MAFF issued precautionary advice on Saturday 14 February advising the public not to handle, slaughter or consume any pigeons within a ten-mile radius of Sellafield.
Results
The results of the initial and more detailed analysis by MAFF of birds sampled are contained in the tables. The group of Seascale sanctuary birds obtained from the RSPCA (K group) were effectively a random selection from the initial cull of 150 birds. The sanctuary birds obtained from the Sellafield site (S group) were selected on the basis of surface radiation levels ( because of safety concerns in handling and transport of the birds to VLA Weybridge) and were therefore expected to give lower levels of radioactivity. The two groups are referred to separately in the tables.
Interpretation
The birds involved at the pigeon sanctuary and those roosting on site are, for the most part, feral pigeons and very unlikely to enter the human food chain. These birds have a range of about 10 miles and roost and feed in the vicinity of man. Some racing pigeons were also in the birds culled; but, once lost, are no different in their habits from feral pigeons. Wood pigeons, generally shot for food, are a separate species, with a woodland habitat. We have found no evidence that pigeons are eaten or that other species of bird which might be taken locally for food have been affected.
At the VLA the initial treatment was to separate the feathers and feet from the birds, as it was possible that much of the contamination was on the surface of the bird. From these initial results (table 1 and table 2) it is clear that the activity is also concentrated in the carcass of the bird. Additionally, some of the K Group of birds showed low levels of other radionuclides in feathers (table 3).
More detailed analysis of these samples showed that some birds had significant concentrations of caesium-137 in breast meat ( table 4 and table 5). The highest level being some 40 times the EU Intervention Level. Consuming the breasts of about 20 birds contaminated at this level would lead to a dose of 1 mSv, the public dose limit, in the unlikely event that any were to enter the human food chain.
Further samples from the RSPCA culled birds have been analysed by both the Environment Agency and BNFL. Levels of caesium found are generally consistent with MAFF results but levels of Cs-137 up to ten times higher in breast meat have been found in a few birds.
Radiochemical analysis of the breast muscle from the pigeons showed significant levels of plutonium and americium-241 isotopes (table 4 and table 5) but of much lower radiological significance than caesium. These isotopes would only contribute a few percent of the dose to any consumer of that due to caesium - 137.
Other portions analysed included the large and small intestine to see if the pigeons had been picking up contaminated grit to aid their digestion. Analysis of the intestines from 5 of the most contaminated birds showed that the activity was mainly associated with the breast muscle of the birds (table 6).
Analysis has also been carried out for strontium -90 on selected birds from the more contaminated K Group and these results are given in table 5. The levels seen would contribute less than one percent to the dose received from caesium-137.
Contact Point
Futher information can be obtained from:
Stuart Conney, MAFF, Radiological Safety and Nutrition Division, Room 539, Ergon House, c/o Nobel House, 17 Smith Square, London, SW1P 3JR
tel: +44 (0) 171 238 6100
fax: +44 (0) 171 238 5465
e-mail: s.conney@fssg.maff.gov.uk
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Q&A
A feral pigeon is the name given to interbreeding groups of stock doves and rock doves. The groups inhabit areas near man, for example town centres or industrial complexes, and are reliant on him for food and shelter. The habits of these birds mean that they are unlikely to move more that 10 miles from their home site and are not seen in areas where man would usually hunt for food.
Radiation dose to man is measured in units called "Sieverts". This is equivalent to a large dose of radiation and so sub-units are used, these are millisievert (mSv). The units are also used to evaluate the rate at which the dose is delivered, so a dose rate may be measured in millisieverts per hour. This dose rate is high for the general public, whose dose limit is 1 mSv per year. This may be compared to the average natural background for the UK of 2.6 mSv per year. In this case the radiation dose rate detected at the surface of the contaminated birds was at 1.4 mSv per hour, but this would decrease sharply with distance from the birds.
The public dose limit is the additional dose of radiation from industrial activities that is set down as being acceptable to a member of the public by the International Commission on Radiation Protection and accepted by the European Commission and the National Radiation Protection Board (NRPB) in the UK. The level of radiation exposure takes into account the risk involved with this level of radiation exposure and what might be considered an acceptable risk by a member of the public.
The EU have set maximum permitted levels of different radionuclides in different foodstuffs that would apply in the event of a nuclear accident or emergency. For caesium-137 in meat the maximum permitted level is 1250 Bg.kg
-1. These levels are set to initially protect consumers before a detailed investigation is carried out. In this case they were not applicable as there had been no nuclear accident or emergency and no consumption of feral pigeons has been identified.
Following the initial cull by the RSPCA the inspector was concerned and took the birds to the Sellafield site for monitoring. This revealed significant levels of contamination and a selection of birds was provided by BNFL on MAFF's request (S group). The RSPCA retained some birds and these were provided to MAFF to act as an independent check on the birds provided by BNFL. These samples were sent to VLA for analysis initially by gamma spectrometry and then, following dissection, by detailed radiochemical analysis.
A survey of traders in the area has confirmed that there is no pigeon meat for sale. This supports the findings of a 1994 MAFF funded survey of locally collected wild foods, covering both animal and vegetable products. This produced information on a number of consumers of game, but no-one who consumed wild pigeons.
A MAFF funded survey of locally collected wild foods in 1994 indicated that pheasant, duck and goose were taken for food in the area. MAFF and BNFL sampling of game birds and water fowl since 1983 has not shown any elevated levels of radioactivity. Sampling has been arranged to provide additional assurance that birds that may be taken for food locally are unaffected.
Caesium -137 is a radioactive form of caesium; similar in biological properties to potassium. It is formed during the nuclear fission process and is released from the spent nuclear fuel during reprocessing.
These are transuranic metals. They are produced when uranium is irradiated during its time in the nuclear reactor and are amongst the products from reprocessing.
Strontium-90 is a radioactive from of strontium; similar in biological properties to calcium. It is formed during the nuclear fission process and released from the spent nuclear fuel during reprocessing.
Table 1: S-group pigeon samples received 13-2-98: Gamma scan results (1).
Table 2: K-group pigeon samples received 13-2-98: Gamma scan results (1).
Table 3: K group pigeon samples received 13-2-98: Additional gamma scan results (1).
Table 4: S group pigeon samples received 13-2-98: Gamma scan and radiochemical analysis results (1).
Table 5: K group pigeon samples received 13-2-98: Gamma scan and radiochemical analysis results (1).
Table 6: K-group pigeon intestine samples received 13-2-98: Gamma scan results (1).
Click here to download the Excel version of Tables 1 to 6
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Shift-Click here to download the .csv version of Table 2
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the .csv version of Table 6
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This page was last updated 13 March 1998
