The effects of smoking on the respiratory system is broad, causing immediate damage that persists over a long period of time. This damage occurs each time smoking occurs, and will stack with any previous harm done.
There are many toxins in tobacco smoke, all these chemicals are deposited into the lungs. The first stage of damage occurs when the toxins travel down to the lungs where they leave small burns to critical parts of the respiratory system. This affects everything from the voice box to the tiny hairs that filter the air we breathe.
The next stage of damage occurs to the parts of the lung that uses the air. Smoking harms the ability of these little systems from allowing air into the blood. This is the main reason why smokers find it difficult to exercise. Many years of this damage will lead to emphysema.
The final stage of damage occurs from the long term exposure to the toxic smoke. The chemicals that sit in the lungs will begin to damage the genetic code of each cell. Eventually the cell will mutate into a form that grows uncontrollably and is difficult to destroy. This is commonly known as Cancer, and essentially is runaway growth of cells that our body cannot fight.
When smoking stops not only can the damage be stopped, but the amazing human body can slowly repair the damage. Eventually most of the negative affects can be repaired, so it is important to quit smoking before a line is crossed where cancer and emphysema is likely to develop. Unfortunately, we cannot know for certain when the line of no return has been crossed. So it is critical we stop smoking sooner than later.