Radioactive Seafood (Again?!)
Doc! What’s this I hear about radioactivity in shrimp? I like my shrimp cocktail, coconut shrimp, the occasional shrimp in my omelet, and…well…wherever else I can add them. And what about other seafood? Is this from Fukushima?
So, at work I recently became acquainted with the concept of BLUF, which stands for Bottom Line Up Front. Or, put another way, cut to the chase. So – yes, Cs-137 was found in shrimp sold by an Indonesian company, no it has nothing to do with Fukushima, and it’s not going to hurt you if some of it slips through the recall and makes its way into your shrimp cocktail. And whew! I’m used to working up to that, so let’s back up a few steps and I’ll explain all of that.
To start (quoting an FDA advisory), a bag of shrimp was found to be contaminated with small amounts of Cs-137 from an as-yet unknown source. To be safe, the company issued a recall and FDA issued an advisory. So the question is how much radioactivity was found in the shrimp and how much of a risk it might pose.
According to the FDA the amount of Cs-137 came out to 68 Bq/kg (0.0018 µCi in units I’m more familiar with). So if you eat a kilogram (about 2.2 pounds) of contaminated shrimp you’ll ingest about 0.0018 µCi of Cs-137, which is comparable to the amount of natural K-40 you’ll find in that same bag of shrimp, and which does not pose a threat to anyone’s health.
“And how not-much is that risk?” (I hear you ask). Well, the Nuclear Regulatory Commission tells us that, to get a whole-body radiation exposure of 5 rem we’d have to ingest 100 µCi of Cs-137 – you’d need to eat over 50 tons of shrimp to get a dose of 5 rem, a dose that’s not all that bad. So let’s say that again – you’d need to eat more than 50 tons of this shrimp – more than any of us is going to eat in a lifetime – to get a radiation dose that’s not dangerous. Which means that if you eat just one kg (still more than two pounds of shrimp!) your radiation dose will be about a tenth of a millirem. So, unless you’ve got the appetite of a blue whale, you don’t need to worry, even if a kg or two of this shrimp slips into your shopping cart. Which makes me happy because I like shrimp too!
As to where the Cs-137 came from…I’m not sure., but I’m pretty sure it’s not from Fukushima (the waters of the North and South Pacific don’t mix much at all). A colleague told me she’d heard it might be from a smelter accident, which is plausible – it’s not uncommon for an abandoned device – maybe a soil density gauge, a tank level gauge, or something along those lines – to end up being tossed in with a batch of scrap metal by someone who simply doesn’t know what it is. And if that load of scrap is sent to a smelter that doesn’t scan for radioactivity the gauge can end up being melted down and the volatile cesium goes out the stack, sometimes drifting out to sea to settle on the water and drift down to the bottom. But it could also have been accidentally washed down a drain at a facility that makes (or recycles) radioactive sources, or might even have been lying in the seabed for the last half-century and more, deposited from a past nuclear weapons test, just waiting to be exposed by some burrowing sea creature (do shrimp burrow?). But wherever it came from, it’s not enough to hurt shrimp eaters anywhere.
And I guess that gets us pretty much to the end of this particular story! So, to recap quickly:
- There was some Indonesian shrimp found to be contaminated with trace amounts of Cs-137,
- The company has recalled much more shrimp than was found to be contaminated, just to be on the safe side, and
- The amount of Cs-137 found in the shrimp was far too low to be dangerous, even if you were to eat 50 tons of the stuff
So not to worry!