I read somewhere that the average human has 0.1 milligrams of uranium in their body. How did it get there, and does it do anything?
In: Biology
Uranium’s just another element. It was floating around in space with all of the other dust before Earth even formed, it was in the lava and the stone and the water as our distant ancestors first crawled from the sea, and it still is.
It’s in the minerals we eat, the water we drink, and even a teensy tiny bit as dust in the air we breathe. Just… Very very very small amounts.
Uranium is everywhere, it’s a naturally occurring element, making up 2.8 parts per million in the Earth’s crust. For a 100kg person (100,000,000 mg) that ratio would be 2.8g. So humans have less uranium than the average chunk of dirt. It’s mostly in bones, slowly decomposing, not doing much harm. You get it from dirt on/in food, and the body has mechanisms that eliminate most of it in urine, that’s how you keep your “less than dirt” concentration.
It got there because it’s in our food and water. Uranium is a naturally occurring element. It exist in tiny amounts in the soil. Plants that grow in that soil take up tiny amounts of it into their roots, leaves, fruits, and stems. We eat those plants or we eat animals that ate those plants. It also exists in rocks and soil and dirt in the rivers and reservoirs we get our drinking water from. That water absorbs tiny amounts of it on its way to your glass of water or cup of coffee.
It doesn’t do anything. It’s just there. The same way every time you eat a banana you’re ingesting a bit of radioactive potassium 40. Our bodies naturally have tiny amounts of a bunch of different radioactive isotopes. They don’t do anything, they’re just there. These isotopes exist in our bodies in such tiny quantities that they aren’t anything to worry about. It’s just a part of life.
Uranium is found in the earth and rocks. It can get into food, and you ingest it.
Uranium-238 is really weakly radioactive, and U-235 isn’t too much worse. If you ate lots of uranium, you would die from heavy metal poisoning at much smaller doses than would be needed for radiation poisoning.
The 0.0001g isn’t going to do much It takes about 5g to give you a 50% chance of dying. The LD50 of salt is 240g for an 80kg person, so it would be equivalent to worrying about eating 5mg of salt. Or 80 grains of salt.
I have worked in labs that sometimes use uranium. At least one time I have probably eaten KFC without washing my hands after leaving the lab. That’s where mine is from. Not sure about normal people though.
That’s just an average. There’s a single guy made entirely out of uranium walking around who’s pulling it up for the rest of us.
Also, do not ask about The Uranium Man.
This is a very small amount, and the radioactivity of U-238 is very mild. One can calculate how much radiation this would generate: it is about one single decay (an alpha-ray particle emitted) per second – which is negligible. So that uranium is essentially doing nothing of consequence.
For comparison: the largest contributor to typical humans’ radiation exposure comes from Radon in the air. That yields about 100 decays per second per cubic meter (i.e. 35 ft3 for Americans)!
>How did it get there
Through food.
> and does it do anything?
Yes. It exists.
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