How do carcinogenic substances cause cancer? What happens in your body?
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Cells reproduce, and when they do, they copy their DNA to the new cell. Sometimes it’s not a perfect copy, and you get a mutant cell. Most of those mutants die on their own or get killed by the immune system. Your body’s probably killing mutant cells right now.
But sometimes a mutant survives, doesn’t trigger the immune response, and even reproduces. That’s cancer. Given enough cells reproducing over enough time, it’s pretty much a certainty that it’ll eventually happen if you don’t die of something else first. That’s just nature and statistics.
Carcinogens don’t actually cause cancer, what they do is increase the odds of it happening whenever your cells reproduce. They affect the DNA or the copying process, increasing the statistical chance of cell reproduction turning out wrong and resulting in a surviving, reproducing mutant.
More exposure to carcinogens increases the number of cells affected and the chances of cancer developing. If something increases the odds enough that many people exposed to it get cancer before dying of something else, then we call it a carcinogen. And some people say it ’causes’ cancer. But really the cause of cancer is just the innate imperfect nature of cellular reproduction. Carcinogens are just a catalyst that increase the odds of imperfection.
Recently, we’ve discovered something really interesting. [Peto’s Paradox](https://en.wikipedia.org/wiki/Peto%27s_paradox) – larger animals have more cells, and therefore more cellular reproduction happening, so they should have a higher chance of getting cancer.
But they don’t. In fact, it seems to be exceptionally rare in elephants and whales. And there’s a lot of research going on into why that is. Currently it seems like they’re just better at killing mutant cells before they reproduce and form tumors. But there could be more to it than that. One theory is that the tumors themselves get tumors which kill them off. There are other theories too. It’s an interesting ongoing area of research where we don’t really know the answers yet.
see also: [Why Blue Whales Dont Get Cancer – Peto’s Paradox](https://www.youtube.com/watch?v=oV1SlzDnS-A) for a good explanation.
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