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Earlier this week, the Food and Drug Administration advised the public not to eat certain Great Value–brand raw frozen shrimp products for a rather unusual reason. Not because of contamination by bacteria like Salmonella, Listeria, or E. coli, which were responsible for more than a third of food recalls last year—but due to the shellfish containing Cesium-137, a radioactive isotope. Yes, radioactive.
U.S. authorities detected the substance in shipping containers coming from Indonesia at four ports of entry (Los Angeles, Houston, Miami, and Savannah). Further testing revealed a small amount of the Cesium-137, or Cs-137, actually in one sample of breaded shrimp (at which port, they didn’t say). The discovery was enough for the FDA to recommend that Walmart stores stop selling specific Great Value shrimp products, and to block imports from the company distributing the product until an investigation is complete. No contaminated shrimp made it to the shelves, that we know of.
Further, the amount of Cs-137 detected in the one batch of breaded shrimp was really quite low. The FDA’s “Derived Intervention Level”—the point at which scientists have determined that protective measures need to be put in place—for Cs-137 is 1,200 becquerels per kilogram (becquerels are a unit of radioactivity). The prawns measured in at approximately 68 becquerels per kilogram. “At this level, the product would not pose an acute hazard to consumers,” the FDA wrote in their announcement.
All to say: You are safe from the “radioactive shrimp,” as they’re being called. But if it all seems a bit weird? It is. “This is very, very unique, in my initial reading of the situation,” says Suresh Pillai, a microbiologist involved in food safety research and director of the National Center for Electron Beam Research at Texas A&M University. “This is not normal.” (Also, technically, “radioactive” describes the activity of the ion, not the item that is contaminated with a radioactive material, Pillai told me. The right phrase here, rather than “radioactive shrimp,” would be something like “shrimp tainted with a material that is radioactive,” which sadly just does not roll off the tongue.)
That Cs-137 exists in the environment is a well-known fact. A product of nuclear detonations, the man-made isotope was released into the environment during nuclear weapon testing in the 1950s and ’60s, as well as nuclear events such as Chernobyl in 1986 and Fukushima in 2011. Cs-137 dissolves easily in water, so it can be found everywhere from soil to rainfall to the air. Still, “it should not show up in food,” says Pillai. “It is strange.”
If the contamination level was well below the FDA’s level of concern, though, why all the fuss? Sure, there would have been no acute health risk from that amount, but there are long-term risks associated with repeated low-dose exposures—in particular, damage to cells and an increase in cancer risk, which is why it’s important to minimize exposure from any radiation, whether it comes from an X-ray or the sun. The most worrisome part of all this, though, is that it’s not clear where the Cs-137 could have come from, and whether that source could still be a contamination risk. The product “appears to have been prepared, packed, or held under insanitary conditions whereby it may have become contaminated,” the FDA wrote in its announcement. Did the shrimp accumulate the isotope from a contaminated body of water? Or did it come from an aerosol that settled on the shipping container? The FDA “is working with Indonesian seafood regulatory authorities” to get to the bottom of it; Pillai and others in the nuclear research space are keeping a close eye. A few “radioactive shrimp” might not pose a health threat, but if they or a similar item were to keep making appearances in the food supply, they could.
That’s not likely to happen, though, given the robust monitoring protocols at U.S. ports of entry. Indeed, the fact that these shellfish were caught at all is actually really good news. “Only 10, 15 years ago, they would not have detected it because the analytical instruments were not as sensitive,” says Pillai. “The ability of U.S. science and technology to detect such low levels— that is, for me, something to be celebrated.”
I will leave you with the answer to a burning question I had as I reported this piece: When a shrimp is contaminated with radioactive materials, does it glow? “Radioactive decay does not typically produce visible fluorescence, so, no,” wrote Megan Cook of the Australian Radiation Protection and Nuclear Safety Agency in an email. Alas! The funkiest thing a “radioactive shrimp” would do—that is, if you put a radiation sensor over such a crustacean, says Pillai—is beep.
