While this is a very good answer I would not agree with:

>If you don't have any known predisposition towards cancer, then it's probably not something to worry about.

There are certainly things that massively increase your relative risk of cancer even if you don't have a genetic predisposition. I know you already said that exposure to strong carcinogens may cause you to develop cancer, and this may be talking about specifically things like cosmic rays, but the context of this sentence as a stand alone paragraph in your answer makes it sound like a more broad statement.

Smoking is definitely something that will significantly increase your risk of cancer even without a genetic predisposition to an extent that it's entirely appropriate to worry about it. If you have a genetic predisposition it's worse but it's still worrisome without one. There are others too but this is a big one in terms of common lifestyle factors.