The principal function of the lungs is to exchange gases between the air we breathe and the blood. The importance of d lungs can not be over emphasized as life is not possible without the lungs functioning well and the worst thing that can happen to any pair of lungs is CANCER.
Cancer of the lung, like all cancers, results from an abnormality in the body's basic unit of life, the cell. Normally, the body maintains a system of checks and balances on cell growth so that cells divide to produce new cells only when new cells are needed. Disruption of this system of checks and balances on cell growth results in an uncontrolled division and proliferation of cells that eventually forms a mass known as a tumor.

Tumors can be benign or malignant; when we speak of "cancer," we are referring to those tumors that are malignant. Benign tumors usually can be removed and do not spread to other parts of the body. Malignant tumors, on the other hand, grow aggressively and invade other tissues of the body, allowing entry of tumor cells into the bloodstream or lymphatic system and then to other sites in the body. This process of spread is termed metastasis; the areas of tumor growth at these distant sites are called metastases. Since lung cancer tends to spread or metastasize very early after it forms, it is a very life-threatening cancer and one of the most difficult cancers to treat. While lung cancer can spread to any organ in the body, certain organs -- particularly the adrenal glands, liver, brain, and bone -- are the most common sites for lung cancer metastasis.

Why do you need to avoid lung cancer?
It is true that lung cancer can be treated with a combination of surgery, chemotherapy, radiation therapy and a few newer experimental methods yet lung cancer is a very dangerous and terminal disease and its the number-one cause of cancer deaths in both men and women worldwide with overall survival rate below 16%.
The major cause of lung cancer is smoking;
Smoking cigarettes is the single biggest risk factor for lung cancer. It is responsible for about 90% of all cases.
Tobacco smoke contains more than 60 different toxic substances, which can lead to the development of cancer. These substances are known to be carcinogenic (cancer-producing).
If you smoke more than 25 cigarettes a day, you are 25 times more likely to get lung cancer than a non-smoker.
While smoking cigarettes is the biggest risk factor, using other types of tobacco products can also increase your risk of developing lung cancer and other types of cancer, such as oesophageal cancer and mouth cancer. These products include:

cigars
pipe tobacco
snuff (a powdered form of tobacco)
chewing tobacco

Smoking cannabis has also been linked to an increased risk of lung cancer. Most cannabis smokers mix their cannabis with tobacco. While they tend to smoke less than tobacco smokers, they usually inhale more deeply and hold the smoke in their lungs for longer.
One researcher has estimated that smoking four joints (homemade cigarettes mixed with cannabis) may be as damaging to the lungs as smoking 20 cigarettes.
Even smoking cannabis without mixing it with tobacco is potentially dangerous. This is because cannabis also contains substances that can cause cancer.
Passive smoking
Even if you do not smoke, frequent exposure to other people’s tobacco smoke (passive smoking) can increase your risk of developing lung cancer.
For example, research has found that non-smoking women who share their house with a smoking partner are 25% more likely to develop lung cancer than non-smoking women who live with a non-smoking partner.
We dont gain much from smoking but lose a lot and might even pay with our life, so, why not quit smoking today.
Smokers are liable to die young.
asbestos-cancerin..com

Nice one!..got me seriously thinking..hey maan i'm outa cigarretes and weeds 4rm now henceforth

Persistent cough for >3 weeks or coughing blood = Get yourself to a doctor!

An aside: There is also a causal link to Cannabis and Schizophrenia. A lot of my mother's generation smoke w33d (I'm from the Caribbean, it happens), but I have observed that the mental health issues are more prominent in my own, younger, generation. The Rastas I grew up with are doing just fine