The major features of the lungs include the bronchi, the bronchioles and the alveoli. The alveoli are the microscopic blood vessel-lined sacks in which oxygen and carbon dioxide gas are exchanged.

Like most vitamins, vitamin B3 (niacin) may be obtained in the recommended amount with a well-balanced diet, including some enriched or fortified foods.

Pyridoxine, or vitamin B6, boosts the manufacture of antibodies to support the immune system. Large doses of B6 can cause numbness and neurological problems.

Ascorbic acid, or vitamin C, aids in many functions of the body, including the absorption of iron. Large doses of C do not usually cause toxicity because, as a water-soluble vitamin, it is simply excreted in the urine. People who tend to form kidney stones may find their condition aggravated by vitamin C supplementation or megadosing.

Secondhand smoke has been classified as a known cause of lung cancer in humans (Group A carcinogen).