There’s two kinds of damage here – acute and chronic. Chronic damage is the slow, incremental stuff. Each smoke chips away at your lungs just a little bit more, weakening them just a little bit. It turns out that the human body is actually pretty good at healing this sort of damage! It can slowly rebuild itself, going back to normal over a pretty long while. Acute damage is what you really need to look out for. This is where you suddenly get a massive amount of damage all at once. It’s like a balloon popping – all the bad stuff happens suddenly, but it was caused by the gradual stuff. This can include cancer, strokes and heart disease. Your body really can’t come back from these. It has no real mechanism to heal itself from stuff like this.
TLDR: Some damage can be irreversible, but there’s no way to know how long it will take.
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