No toxic effects appear to be associated with carbon in its elemental form. On the other hand, many of the more commom carbon compounds exhibit strong toxicological effects. Principal among these are carbon monoxide, carbon dioxide, hydrogen cyanide and the alkali cyanides, carbon tetrachloride and carbon disulfide.

Carbon monoxide, an odorless gas, is extremely toxic, behaving as an asphyxiant. Compared to oxygen, it is not only more readily absorved, but also more firmly bound by the hemoglobin of the blood. The capacity of the blood to carry oxygen to the vital parts of the body is thereby reduced, leading to brain damage, heart disease and pneumonia.

Carbon dioxide is less toxic and behaves chiefly as a simple asphyxiant and narcotic.

Hydrogen cyanide and the alkali cyanides are extremely toxic, functioning as protoplasmic poisons by inhibiting tissue oxidation.

Acute exposure to the vapors of carbon tetrachloride can result in damage to both the liver and kidneys. Carbon disulfide is a powerful narcotic, but its chronic effects are more serious. Excessive exposure can lead to permanent damage to the nervous system.