The tobacco plant produces its own insecticide to protect it. This insecticide is called nicotine and it is very effective. If you brush up against a tobacco leaf it will leave a brown gooey substance, this is mainly nicotine.
Tobacco is produced by drying the leaves under controlled conditions. This process concentrates the nicotine in the tobacco, the stuff that you smoke.
This was well known in the past and tobacco was often used to kill pests in the garden or on crops. At one stage, it was common to soak cured tobacco leaves in water and then spray that water over the crops to kill the pests.
If you read any gardening books from the 40’s and 50’s they say to take a container of water. Put your cigarettes butts in it and a few unsmoked cigarettes, let them stew for a few days and then spray the water over the garden to combat pests. Works like a charm.
If you want to see this for yourself then take a few cigarettes, place them in a mug of water and wait about 15 minutes. You will see a brown residue at the bottom of the mug, this is nicotine and it is extremely poisonous.
You might say that if I’m smoking poison how come it has not killed me? The answer is that it does not kill you immediately as the heat of your body causes the nicotine molecules to change. However, the nicotine is still affecting your health as it causes your blood vessels to constrict. This means that the blood supply to your body is restricted. This in turn means that your blood pressure jumps up and exposes you to stroke.
If I was to ask you to take an insecticide from a shop and drink it, you wouldn’t because it would harm you. When you smoke, this is what you are doing, you are self-harming. It makes sense to quit smoking and to breathe fresh air. It makes sense to stop smoking a pesticide.