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

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

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42 Answers

Anonymous 0 Comments

A lot of the carcinogens are produced by burning the leaves rather than just existing within the leaf on its own.

You’ll get things like tar and soot which are carcinogenic if you burn other natural materials like wood or tree leaves too – it’s not unique to tobacco.

The main differences with tobacco are the frequency with which people burn it (multiple times daily whereas most people wouldn’t have a bonfire even weekly); and the way people deliberately inhale the smoke deeply to get the effects of the nicotine in their body.

Bringing the smoke into the lungs on purpose means that carcinogens which you’d usually need to be exposed to in much larger quantities on, say, your skin for them to cause cancer can act more directly on the delicate lung tissue.

Anonymous 0 Comments

Plants make all kinds of weird chemical compounds to make them poisonous and prevent them from being eaten by bugs and deer and things like that. Those compounds do things to the body. Plus when its burned chemical reactions happen that change the structure of a lot of it into other things, which are harmful.

Anonymous 0 Comments

Plants make all kinds of weird chemical compounds to make them poisonous and prevent them from being eaten by bugs and deer and things like that. Those compounds do things to the body. Plus when its burned chemical reactions happen that change the structure of a lot of it into other things, which are harmful.

Anonymous 0 Comments

Nicotine, the active ingredient in tobacco, is created by the plant to prevent things from eating it. Often irritants to insects and animals (yes, insects are animals, but they’re important to point out in particular) end up being cancer-causing both because of how they irritate, and because the more damage they do the more likely the predator is to avoid the plant either by learning or through evolution.

Also, generally tobacco is smoked, so any warning related to its chemical composition will be in the context of those chemicals entering the lungs. Generally most chemicals are dangerous in the lungs: people who inhale soot from a house fire are also at a higher risk of cancer. Since tobacco is usually smoked, even if you’re not buying a smokeable version, the testing for if the chemicals are cancerous was likely done regarding cigarettes. (This doesn’t mean that there’s no risk, though. Chewing tobacco is still known to increase the risk of cancer.)

Anonymous 0 Comments

Nicotine, the active ingredient in tobacco, is created by the plant to prevent things from eating it. Often irritants to insects and animals (yes, insects are animals, but they’re important to point out in particular) end up being cancer-causing both because of how they irritate, and because the more damage they do the more likely the predator is to avoid the plant either by learning or through evolution.

Also, generally tobacco is smoked, so any warning related to its chemical composition will be in the context of those chemicals entering the lungs. Generally most chemicals are dangerous in the lungs: people who inhale soot from a house fire are also at a higher risk of cancer. Since tobacco is usually smoked, even if you’re not buying a smokeable version, the testing for if the chemicals are cancerous was likely done regarding cigarettes. (This doesn’t mean that there’s no risk, though. Chewing tobacco is still known to increase the risk of cancer.)

Anonymous 0 Comments

Just 70? They’ve cut down, then.

The tobacco in cigarettes has been treated with a raft of additives before packaging, and that is where most, but not all, of the substances come from.

IF you look on a package of decent cigars, you will not find as many. Because cigars are simply tobacco leaves, rolled into other tobacco leaves, and sold. There is no “processing” of the leaf to speak of, not add chemicals to it.

Anonymous 0 Comments

Just 70? They’ve cut down, then.

The tobacco in cigarettes has been treated with a raft of additives before packaging, and that is where most, but not all, of the substances come from.

IF you look on a package of decent cigars, you will not find as many. Because cigars are simply tobacco leaves, rolled into other tobacco leaves, and sold. There is no “processing” of the leaf to speak of, not add chemicals to it.

Anonymous 0 Comments

Just 70? They’ve cut down, then.

The tobacco in cigarettes has been treated with a raft of additives before packaging, and that is where most, but not all, of the substances come from.

IF you look on a package of decent cigars, you will not find as many. Because cigars are simply tobacco leaves, rolled into other tobacco leaves, and sold. There is no “processing” of the leaf to speak of, not add chemicals to it.

Anonymous 0 Comments

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

Anonymous 0 Comments

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