The 210Po content of North Sea edible crab, Cancer pagurus L., and common shrimp, Crangon crangon L. and the potential radiological impact

Abstract The 210 Po 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 210 Po. There was no statistically significant variation in the brown meat 210 Po content of female crabs over the period of the study. However, there was a statistically significant variation in the brown meat 210 Po content for males, but there was no clear pattern with time. Male claw muscle contained less 210 Po than female and was more variable with time, although, again, without a clear pattern being visible. The median individual effective dose equivalent for 210 Po 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 × 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 μSv. The equivalent mean value for an average weight of dressed crab (135 g wet weight) was 1·1 μSv (range 0·6–2·2 μSv). The mean concentration factor for 210 Po in edible crab brown meat was calculated as 2·7 × 10 4 (range1·0–4·7 × 10 4 ) and for claw muscle 590 (range 3·0 × 10 2 –1·3 × 10 3 ). These results show that the IAEA recommended value for crustacea, 5 × 10 4 , can overestimate the accumulation of 210 Po in the edible fractions of some commercially important crustacean species.