Smoke from the tobaccoo products, contains nicotine
, Tar products and other carcinogenic agents which affects, your Respiratory tract
, cardiovascular sustem, and Aero-digestive tract to just name a few. The diseases, may be like, COPD, ASTHMA
, BREATHING DIFFICULTY, Leukoplakia
, or ORAL CANCER
and LUNG CANCERS .
Now the golden question, that is why some people who smoke a lot still don't get any diseases, just mentioned.
The ANSWER is that, smoking
is CONSIDERED TO BE MOST IMPORTANT RISK FACTOR in causation of all such diseases. But all these diseases have multiple etiologies (factors leading to diseases). these are like INDIVIDUAL GENETIC MAKEUP, IMMUNE SYSTEM, OVERALL HEALTH BEING, EXPOSURE TO OTHER RISK FACTORS like VIRUSES, RADIATIONS, CHEMICALS etc.
RISK FACTOR means having exposure to that factor INCREASES your chances by many fold FOR GETTING that disease. Doesn't mean that you will get the diseases for sure after exposure. Because as alraedy told, getting the diseases depends on other factor as well. It is very similar to like, "not wearing HELMET on bikes, increases your chances for head injury
in case of an accident, but doesn't mean that if you don't wear helmet, you will have an accident and get head injury".
also, smoking causes, genetic mutations, which can DEACTIVATE tumor supressor genes p-53, which keeps in check growth of any unwanted tumor activity. Such deactivation may lead to development of CANCERS.
Lastly, there is NOTHING like Numbers of Ciggerattes, ne can have safely without any diseases. even a single Cigeratte may prove as DANGEROUS as a truck load of them.