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 in monthly samples over one year to investigate possible seasonal changes. The highest value measured in shrimp was found in August for hepatopancreas tissue. Tailmuscle values were significantly lower than those 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 statistically significant difference was found between male and female crab brown meat Po-210. There was no statistically significant variation in the brown meat Po-210 content of female crabs over the period of the study. However, there is a statistically significant variation in the brown meat Po-210 Content for males, but there was no clear pattern with time. Male claw muscle contained less Po-210 than female and was more variable with time, although, again, without a clear pattern being visible. The median individual effective dose equivalent for Po-210 from eating 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 Bq-1. The equivalent value for eating dressed crab (mixed crab brown meat 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 effective 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 (range 0.6-2.2 muSv). The mean concentration for Po-210 in edible crab brown 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 that the IAEA recommended value for crustacea, 5 x 10(4), can overestimate the accumulation of Po-210 in the edible fractions of some commercially important crustacean species.