Harmful substance in a cigarette what causes disease?
The nicotine is the addictive substance, however it is the tar
within the cigarette which is harmful to the human body. This tar
sufficiently reduced the surface area of the alveoli to perform gas
exchange. This black tar fills up and blocks the lungs making it
harder for the smoker to breathe - causing breathlessness. This tar
build up also leads to heart diseases and such.