Beryllium is the fourth element in the periodic table and is a light, brittle, and gray alkaline earth metal. Beryllium is found naturally in coal, rocks, dust, and soil and is typically bonded with other elements. It is released into the environment through dust, airborne particles, and the combustion of fossil fuels. Because of its high melting point, strength, and lightweight nature, it is commonly used in aerospace materials, electronics, defense technologies, X-ray equipment, and as an alloying element in conjunction with other metals such as copper, iron, or nickel.

The general public can be exposed through waterways, food, air, and accidental soil contact or ingestion. However, most beryllium exposure and resulting beryllium toxicity result from occupational exposure via inhalation, resulting in pulmonary disease.

Acute beryllium toxicity, an acute chemical pneumonitis, has been reported after high-intensity exposures. Cases have become rare after increased government regulations were set into place.

Chronic beryllium disease, also known as berylliosis, is a pulmonary granulomatous disease that occurs in sensitized individuals. It is mediated via a type IV hypersensitivity reaction.