Silly. That’s an I-131 mitigation from a nuke detonation. Likely dirty bombs will be particles of radioactive cesium, strontium, amerecium, cobalt, tritium from commercial sources.
That’s what I was thinking. Unless they bust open a nuclear reactor or detonate a real nuke, this is pointless. I’m not against personally having a few bottles of iodide around just in case, but it’s not going to protect from any conceivable dirty bomb.