What is cigarette tar?

Tar is a sticky brown substance that forms when tobacco smoke cools and condenses. About 80% of this tar is deposited in the lungs and many of the substances in tar are known to cause cancer. Irritants in tar also damage the lungs by causing narrowing of the bronchioles, coughing, an increase in mucus and damage to the small hairs (cilia) which help protect the lungs from dirt and infection.