Cigarettes are harmful in three ways, they contain:

1.Nicotine – addictive drug that leads to heart disease. Nicotine raises blood pressure and narrows arteries

2. Tar – coats the lining of the lungs > less O2 is absorbed. Tar contains carcinogens which cause cancers

3. Carbon monoxide – poisonous gas which joins onto red blood cells making them incapable of transporting oxygen around the body