Carcinogens mostly cause small increases in the probability of cancer. GP is right; the main cause of cancer is "being old". It's true that, if you eliminated e

Carcinogens mostly cause small increases in the probability of cancer. GP is right; the main cause of cancer is "being old". It's true that, if you eliminated every source of DNA damage and miscopying, cancer wouldn't happen; but even if you eliminated all external carcinogens, that wouldn't stop the process, just slow it a bit.