Earlier this week, the Food and Drug Administration announced that some bags of Walmart’s Great Value frozen shrimp might have been contaminated with Cesium-137. Yes, that’s the same Cesium-137 from the Chernobyl and Fukushima nuclear accidents.

So, how did it get into the shrimp? We don’t know.

But we’ve got some good news. Even if you somehow ate shrimp tacos with the suspect crustaceans, you’re probably not going to start glowing green like a Marvel origin story. The FDA says the detected levels are way below the dangerous threshold.

Why Is There Cesium On My Shrimp?

Earlier this month, the U.S. Food and Drug Administration (FDA) dropped a surreal advisory: certain bags of Walmart’s Great Value frozen shrimp, imported from Indonesia, lit up with Cesium-137 — a byproduct of nuclear fission.

Customs and Border Protection flagged some shipping containers from Indonesia’s BMS Foods after scanners picked up radioactivity at four U.S. ports — Los Angeles, Houston, Miami, and Savannah. FDA labs tested the shrimp inside and found that one batch of breaded shrimp was contaminated by nuclear material.

That particular shipment never made it onto Walmart shelves, but regulators still slapped a warning on shrimp lots sold in 13 states. The official FDA advice couldn’t be clearer:

“If you recently purchased one of the impacted lots of Great Value raw frozen shrimp from Walmart, throw it away. Do not eat or serve this product.”

Nobody actually knows how the shrimp got contaminated.

The FDA’s advisory delicately says the seafood “appears to have been prepared, packed, or held under unsanitary conditions.” Translation: somewhere between Indonesia and your local Walmart, the shrimp was probably hanging out in a dirty shipping container that once stored something much nastier.

Scientists on the social media platform Bluesky offered theories. UC Berkeley health physicist Phil Broughton guessed it was just industrial corner-cutting: companies reusing shipping containers without bothering to clean them. Planetary scientist Michael Busch chimed in that the contamination probably happened in the supply chain, not in the shrimp pond. With so little information, all we’ll likely get is speculation.

But what happens if you did eat radioactive shrimp?

How many radioactive shrimp can you eat?

Cesium-137 is a man-made isotope, born in the fires of nuclear reactions. In trace amounts, it’s everywhere. But concentrated exposure is another story. Short-term, high doses can cause radiation burns and acute sickness. Long-term, even at low levels, the danger is more insidious as the isotope lodges in your body, where its radiation can chip away at your DNA, raising the risk of cancer. Simply put, Cesium-137 is made in nuclear reactors. It doesn’t belong in food. Ever.

But as always, the dose makes the poison.

FDA labs followed up and confirmed it in one sample of breaded frozen shrimp: about 68 becquerels per kilogram. That sounds like a lot, but is it?

A becquerel (Bq) just counts how many atoms decay per second. It doesn’t measure what kind of radiation is coming out (alpha, beta, gamma) or how dangerous it is to your body. Different isotopes have different safety levels. For Cesium-137, the FDA considers a food to be dangerously contaminated once it reaches 1,200 Bq/kg. In Europe, a common safety threshold is considered to be 100 Bq/kg. That’s a much more stringent limit, but even that is more than what the shrimp clocked.

Still, that doesn’t mean you should eat the shrimp; not at all. But it does mean that if you ate one or two, you’ll probably be fine. Just make sure not to stockpile on the “Great Value” shrimp, no matter how great the value.

Poisoned Prawn Politics

There’s a strange irony in all this. This whole circus is happening under the watch of Robert F. Kennedy Jr., now head of Health and Human Services. Yes, the same RFK Jr. who once ate so much fish he gave himself mercury poisoning, and who spent years crusading against vaccines, is telling people not to eat radioactive shrimp. Somewhere, the universe is laughing.

However, on a more serious note, this one contaminated shipment, a small incident that has already been recalled, exposes bigger cracks in our food system. Global supply chains are messy. When most of what you eat comes from halfway around the world, the system is only as good as the weakest link in the chain. If someone got lazy and reused a box they shouldn’t have, you can end up with radioactive shrimp. Or even worse, you can end up with something just as dangerous but harder to detect (like bacteria).

Food safety is built on vigilance. The FDA caught this batch, but if the agency is weakened, which is exactly what RFK Jr. is doing, the next batch might slip through the cracks; and it could have more than 68 becquerels.

This was a minor scare, although no one really wants to hear the words “radioactive shrimp.” But the threat is very real, and it’s an everyday reality. Our food systems are just built that way, and we can’t afford to let our guard down.