Yes. It does depend on concentration. Shrimp naturally contain radioactive potassium 40, as well as polonium.
All living things contain 40K without which they would die, since potassium is an essential element. The polonium in shrimp is a function of the fact that the oceans naturally contain about 4.5 billion tons of uranium, which is in secular equilibrium with polonium, a decay product.
This point was covered some years back, in the post Fukushima brouhaha, when the lives of tuna were being saved by human paranoia over the presence of another isotope of cesium, the more radioactive 134Cs in response to another paper written by the authors of this one: N.S. Fisher,K. Beaugelin-Seiller,T.G. Hinton,Z. Baumann,D.J. Madigan, & J. Garnier-Laplace, Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood, Proc. Natl. Acad. Sci. U.S.A. 110 (26) 10670-10675.
The authors of the paper were appalled by the generally stupid media frenzy connected with their previous paper.
From the paper cited:
Recent reports describing the presence of radionuclides released from the damaged Fukushima Daiichi nuclear power plant in Pacific biota (1, 2) have aroused worldwide attention and concern. For example, the discovery of 134Cs and 137Cs in Pacific bluefin tuna (Thunnus orientalis; PBFT) that migrated from Japan to California waters (2) was covered by >1,100 newspapers worldwide and numerous internet, television, and radio outlets. Such widespread coverage reflects the public’s concern and general fear of radiation. Concerns are particularly acute if the artificial radionuclides are in human food items such as seafood. Although statements were released by government authorities, and indeed by the authors of these papers, indicating that radionuclide concentrations were well below all national safety food limits, the media and public failed to respond in measure. The mismatch between actual risk and the public’s perception of risk may be in part because these studies reported radionuclide activity concentrations in tissues of marine biota but did not report dose estimates and predicted health risks for the biota or for human consumers of contaminated seafood. We have therefore calculated the radiation doses absorbed by diverse marine biota in which radioactivity was quantified (1, 2) and humans that potentially consume contaminated PBFT. The aim of this paper is to provide estimated doses, and therefore objective risk estimates, to humans and marine biota...
If you were born after 1945, every fish or other seafood based animal and/or seaweed in sushi you have ever eaten has contained
137Cs from the era of open atmosphere nuclear testing. You are nonetheless, even if you have eaten seafood products, still alive.
