How much of a dose of radiation do you get by snuggling up against your significant other for a year? Unless they’re glowing green, it’s a small dose, but it’s not nothing. We’ll tell you how much radiation you, and the people around you, emit.
Radiation isn’t only made by humans. Naturally-occurring radioactive particles are all over, and we absorb them into our bodies constantly. Sometimes we absorb them by accident, as when our body mistakes strontium-90 for calcium and puts it in our bones and teeth. Other times, we build our bodies out of radioactive particles because they’re isotopes of elements we need. When the Fukushima disaster happened, children were given iodine-127 tablets. Their bodies stored the iodine in their thyroids, until the thyroid reached iodine saturation, at which point the kids excreted the rest of the iodine. They also excreted any radioactive iodine-131 that might have been making its way into their system.
Iodine-131, and most other radioactive particles we pick up, emit beta particles—electrons. This decay can damage us when it’s emitted inside of us, but can’t hurt anyone around us. (It couldn’t even do any real damage to us if were outside our body instead of inside of it.) For a human to give a dose of radiation to the person standing next to them, we need gamma radiation—high frequency photons.
The main emitter of these is potassium-40. Potassium-40 is a naturally occurring isotope of potassium. It gets taken up by plants (some of which have a higher affinity for it than others), and when we eat the plants we incorporate it into our bodies. About 5000 atoms of potassium-40 decay in your body every second—a little less if you’re well under 70 kilograms, or 155 pounds. Only ten percent of those decaying atoms give off gamma rays, and only a small percentage of those rays make it out of your body. One reason to lose weight could be the chance to decrease the percentage of those gamma rays that hit you before they make it into the outside world. (Viewed like this, though, dieting is an act of selfishness. If someone in your life is dieting, they’re probably trying to kill you.)
Sleeping next to a person for a year gives you about 1 millirem of radiation. Assuming eight hours of sleep a night, that means a human body gives about three millirem a year of radiation. That’s about what you’d get if you spent nine days in Atlanta or six days in Denver (a higher altitude means a higher dose of radiation). So it’s not time to forswear human company, yet. Or if it is, you’ll need some other excuse.