What if We Go Bananas?

Bananas emit a small amount of radiation due to their potassium. But they are completely harmless; in fact, it would take absurd circumstances for them to become dangerous. But let’s go bananas to explore it!

Bananas contain potassium, an essential nutrient for the human body. A small fraction of naturally occurring potassium is radioactive, in the form of potassium-40.

One banana emits about 0.1 microsieverts. Scientists informally call this measurement BED (Banana Equivalent Dose). For example, you would get a thousand BED from a chest x-ray, and up to 4.000 BED flying from New York to Los Angeles.

It’s safe to eat and store bananas and they pose no danger whatsoever. But let’s consider a larger scale. What happens if you store large quantities, did they become a threat?

U.S. ports routinely set off alarms due to naturally radioactive goods — including bananas due to potassium-40. And in fact, a report to the US congress highlighted the severity of these false alarms of “radioactive threads” back in 2008. But the question remains: in massive quantities, bananas could become a threat?

Short answer… No.

You would need to stand next to a banana mountain for months to equal a single medical scan like the chest x-ray we called out as example above. Most energy would be absorbed by other bananas and while they decay in just a few days, the radiation will spread out too.

But let’s say we could ingest a significant amount to make ourselves sick… Physically, that’s impossible because to reach radiation levels associated with acute illness, a person would need to consume approximately 10 million bananas in a short period of time.

Piled together, 10 million bananas would almost cover the Statue of Liberty (46m without the pedestal), and you would need to eat them before they rot in 3-4 days. And that brings the other problem... as bananas decompose, they release methane — a greenhouse gas significantly more potent than carbon dioxide.

The 10 million banana pile would emit an estimate of about 66,000 cubic meters of methane. This gas has a significant warming effect, more than 80 times the warming power of carbon dioxide.

The real risks with our theoretical experiment would be the odor, biological decay, and greenhouse gas emissions.

Methodology

Radiation estimates
For this comparison, I’m using the Banana Equivalent Dose (BED). Since bananas contain naturally occurring radioactive Potassium-40 (⁴⁰K), Scientists use it as a fun, relatable yardstick. One banana represents roughly ≈ 0.1 µSv of radiation. BED is for illustration only, or if you are a mad scientist. Our bodies naturally regulate potassium, so eating a banana won’t actually spike the radiation exposure.

Banana pile
For the geometry geeks: I assumed a standard banana takes up roughly 120cm³ and weighs ≈120g. When you multiply that by 10 million, you get a 1.2 million cubic meter pile weighing 1,200 metric tons. Picture a mid-sized office building made entirely of fruit. I'm ignoring the squish factor, and for visual purposes I'm using a pile of about 18,000 bananas rendered with threejs to represent the larger quantity. Bananas in the visuals about are about the size of a human... nuts. But this is a fun website after all.

Methane Emissions from decay, a smelly approach
Gas potential comes from standard environmental observations on rotting food. When organic matter breaks down without air (anaerobic), it gets gaseous. Using a mid-range factor of 55 m³ of methane per ton, our 1,200 ton banana pile would generate roughly 66,000 m³ of methane. The Weight: That volume translates to ≈44,000 kg of gas (at 0.67 kg/m³). The Impact: Methane is about 28× more potent than CO₂ over a century. These are broad estimates based on EPA/IPCC standards, not a specific experiment. I did not personally rot 10 million bananas in my backyard to verify this, but I trust the sources below.

Sources

BED contextual comparisons, University of Melbourne Radiation Guidelines. Natural Radioactivity in Food, US EPA. Banana Equivalent Dose, and Potassium-40 background and role, Wikipedia. BED dose calculation and context, Everything Explained. Detecting Nuclear Smuggling, Scientific American. Detecting nuclear weapons and radiological materials: how effective is available technology?, A report on the hearing to the congress of the US pointing out the false concerns of frequency of false alarm “radioactive threat” triggered by bananas. Chemical composition and biochemical features of banana, Research paper by Guylene Aurore, University of the French Antilles.