a couple years ago, some friends and I did some trespassing urbexing around the abandoned railroad tracks in town, and we came across some sort of warehouse-type facility that had a bunch of old medical equipment and office stuff in it. outside the facility, there was what looked like a large antenna, which was fenced off and had a large sign which said something (I forget the exact wording) about how you should keep back or wear protective gear, or maybe something about exposure limits for workers
later, I tried looking up what that was about, since I had previously heard that radio waves are harmless to humans and the people who worry about them don’t know anything about it. but all I got was some snide guy on a forum saying, “well, of course they have effects, everything has effects, but also you’re stupid if you think it does anything”
so like, does anyone know what that sign was about
certain medical procedures use radioactive substances (there’s cancer treatment where you kill cancer with radiation and there’s also medical tracers that are used for diagnosing things by injecting a small amount and detecting the radiation outside the body to see where stuff is collecting/ going, possibly others i’m forgetting). Possibly it’s somewhere that used to be used to produce/ store that stuff.
That’s all true, but it sounds like OP came across this symbol:
This is the warning symbol for non-ionizing radiation. You often see it near powerful antennas, because those can cause RF heating and tissue damage if you get too close. That said, if the facility was abandoned, the antenna was certainly off, so there was no danger.
So is the issue that while visible light is harmless, getting really close to a building-sized lightbulb can still cook your flesh? It’s just the sheer intensity is going to cook you?
Yes, exactly. Let’s do a mini physics lecture here:
When people talk about “radiation” as the thing that gives you cancer, what they mean is ionizing radiation. “Ionizing” here meaning, the radiation can knock electrons free of their atoms. This changes the chemistry of any molecules those atoms happen to be part of, and turn molecules into other molecules, which in turn can do things like mess up your DNA as though you were flipping random bits in a computer.
The key point here is that only X-rays and gamma rays (and some particles which are outside the scope of this post) are ionizing radiation. Radio waves, microwaves, and visible light are non-ionizing. This means that no matter how powerful the radio waves are— even if they were infinitely powerful— they can never knock electrons free of their atoms. The exact reason for this involves quantum mechanics, but the simplified version is that electrons absorb EM radiation in units of individual photons, and when you make radio waves more powerful, you’re making more of these photons but each individual one doesn’t have more energy, so no matter how many there are they can never kick the electrons loose. So even infinitely-powerful radio antennas (or light bulbs) can never cause cancer in the way that radioactive substances can.
But, if the waves are sufficiently powerful, they can also cause damage via plain old heating, in (more or less) the same way as sitting next to a very very powerful light bulb will cook you. As kircheis said, this is why you don’t stick your hand in a microwave — it won’t give you radiation-induced cancer, but it will just cook you. Same thing with really powerful broadcast antennas — no cancer, but just cooking, so stay clear. Fortunately, since power falls off with the square of distance, you don’t need to be very far to be safe — that’s why these antennas just have fences around them rather than some kind of thick radiation shielding.
