system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does something gets contaminated from radiation?

Re-watching Chernobyl and this doubt just got to me after seeing the cloths disposal of the first responder firefighters.

As far as I know radiation works by collision with other's atoms and breaking them, so, how does something that has been affected by this collision become radioactive?
gpt
First off, radiation causes damage by breaking chemical bonds or by knocking electrons off of atoms in a way that causes unwanted chemical reactions, not (usually) by splitting other atoms apart.

But there are two main ways:

One is chemical contamination, where bits of the original radioactive material are mixed in with the other material. For example, small particles of dust containing radioactive metals could contaminate clothes worn at Chernobyl, or radioactive iodine could replace the normal iodine present in a human thyroid gland.

The other is *activation*, where radiation itself turns an atom that was previously not radioactive into a new radioactive form. The most common form of this is neutron activation, where a neutron released by a splitting atom is absorbed by another nucleus, converting the other nucleus into an unable form. For example, non-radioactive Cobalt-59 might absorb a neutron and become the very radioactive Cobalt-60, so that a sample of cobalt near a neutron emitter can become radioactive even if none of the original radioactive material comes along with it.