system
Given the following post, respond as if you're commenting on Reddit:
human
Since children are growing and constantly have dividing cells, why do they have lower cancer rates than adults (who are not growing)?
gpt
Cancer develops when cells malfunction, and when the malfunction is not handled by the immune system.

Cells can malfunction for three reasons: cell was faulty to start with (genetics), cell was exposed to something that causes malfunction (a carcinogen), or cell randomly malfunctions. 

Of those three reasons, genetics and carcinogens are much more likely than random errors. Genetics typically lead to childhood cancers (because cells are faulty from early in life), whereas environmental exposure typically leads to adult cancers (because damage from carcinogens keeps accumulating). 

Also, adults also have constantly dividing cells, even if they aren't growing (but the rate of division is lower than in children).