Hi there , thanks for writing to us. Tobacco and tar in smoking is so hazardous that may lead on to most common diseases affecting the heart, liver and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD), and cancers. It also causes peripheral vascular disease and hypertension. The effects of disease ,depend on the number of years that a person smokes and on how much the person smokes. TAR in smoking is major cause of increasing the risk of these diseases. A person s increased risk of contracting disease is directly proportional to the length of time that a person continues to smoke as well as the amount smoked. So advice him to quit smoking as soon as possible, To know the damage of the smoke caused by smoke,just take him to an physician and assess his health status if you had any queries,let me know. dr.surendiran