eli5: If tobacco is a leaf, why does it have so many substances known to cause cancer?

Question

* Source is the packaging I’ve just read for a pack of tobacco in the UK which says it has 70 cancer causing substances

In: 2

Answer 1

Something being natural doesn’t mean it is safe for human. Poison Ivy is 100% natural but you probably don’t want it in your bedding, and hemlock is 100% natural, but you don’t want it in your food.

In fact, plants that are toxic to certain animals have that as a built in survival mechanism.

The premise that if X is a leaf, X is safe is just not true