THE 210PO CONTENT OF NORTH-SEA EDIBLE CRAB, CANCER-PAGURUS L, AND COMMON SHRIMP, CRANGON-CRANGON L AND THE POTENTIAL RADIOLOGICAL IMPACT

The Po-210 content of brown shrimp and edible crab has been measured i n monthly samples over one year to investigate possible seasonal chang es. The highest value measured in shrimp was found in August for hepat opancreas tissue. Tailmuscle values were significantly lower than thos e in the hepatopancreas but followed a similar trend, with the highest value being measured in August. However, in neither tissue were these statistically significant changes correlated with time. No statistica lly significant difference was found between male and female crab brow n meat Po-210. There was no statistically significant variation in the brown meat Po-210 content of female crabs over the period of the stud y. However, there is a statistically significant variation in the brow n meat Po-210 Content for males, but there was no clear pattern with t ime. Male claw muscle contained less Po-210 than female and was more v ariable with time, although, again, without a clear pattern being visi ble. The median individual effective dose equivalent for Po-210 from e ating North Sea shrimp tail muscle was estimated at about 0.001 mSv a- 1 by using the NRPB recommended dose coefficient of 4.35 x 10(-7) Sv B q-1. The equivalent value for eating dressed crab (mixed crab brown me at and claw muscle) was about 0.02 mSv a-1. A measure of whole shrimp, traditionally one pint (568 ml), was estimated to represent an effect ive dose equivalent of about 0.007 muSv. The equivalent mean value for an average weight of dressed crab (135 g wet weight) was 1.1 muSv (ra nge 0.6-2.2 muSv). The mean concentration for Po-210 in edible crab br own meat was calculated as 2.7 x 10(4) (range 1.0-4.7 x 10(4)) and for claw muscle 590 (range 3.0 x 10(2)-1.3 x 10(3)). These results show t hat the IAEA recommended value for crustacea, 5 x 10(4), can overestim ate the accumulation of Po-210 in the edible fractions of some commerc ially important crustacean species.