Radionuclides in seals and porpoises in the coastal waters around the UK

It has been suggested that marine predators be assessed for biologically re levant contamination levels because of their trophic position. Accordingly, in studying radioactive contamination in the marine environment around the UK, tissues from seals and porpoises have been chosen. Liver and muscle ti ssue from dead seals and porpoises found stranded around the UK coast have been analysed for the following radionuclides: Cs-134, Cs-137, Pu-238, Pu-2 39 +Pu-240. Multifactor analysis of variance indicated that, for radiocaesi um, there was no significant difference for harbour seals, grey seals or po rpoises in terms of species or gender; however, the tissue activity concent ration increased with body weight and decreased with distance from Sellafie ld, the major nuclear reprocessing plant in the UK. The levels of radiocaes ium in muscle were higher than those in liver, while there appeared to be a concentration factor of approximately 3-4 for muscle radiocaesium when com pared to radiocaesium levels reported for fish, the main food source of the marine mammals under study. Approximate radiation dose calculations indica ted that the average dose from radiocaesium was less than 10% of the dose f rom the naturally occurring radioisotope of potassium, K-40. Th, highest ti ssue activity concentration for plutonium of 0.037 Bq/kg (Pu-239 + Pu-240) was detected in a grey seal stranded at Rathlin Island in Northern Ireland. Calculation of approximate radiation doses from plutonium contamination sh owed that, as with radiocaesium, the average dose was small compared with t hat from 40K. I, summary, the radiocaesium contamination in seals and porpo ises decreased with distance from Sellafield indicating that the BNF pie pr ocessing plant was the major source of the contamination. The marine mammal s concentrated radiocaesium from their environment by a factor of 300 relat ive to the concentration in seawater indicating the value of using marine m ammal tissue to measure radiocaesium contamination in the marine environmen t. The maximum radiation dose to the marine mammals from radiocaesium was h igher than doses previously assessed for critical groups of humans living n ear Sellafield, while the maximum dose from plutonium was comparable to the doses for humans. (C) 1999 Elsevier Science B.V. All rights reserved.