Industrially produced hydrogen selenide is a colorless gas with a disagreeable odor. It is probably the only selenium compound that might pose a health concern in the workplace. Selenium dioxide is an industrially produced compound that dissolves in water to form selenious acid. Small selenium particles in the air settle to the ground or are taken out of the air in rain. Soluble selenium compounds in agricultural fields can leave the field in irrigation drainage water.
Selenium can collect in animals that live in water containing high levels of it.
People exposed to very high levels of selenium in have reported dizziness, fatigue, irritation, collection of fluid in the lungs, and severe bronchitis. The exact levels at which these effects occur are not known. Upon contact with skin, selenium compounds have caused rashes, swelling, and pain. In the United States, selenium in most diets is usually enough to meet the daily requirement of this essential metal. In regions of China where soil levels of selenium are very low, diets lacking selenium have resulted in heart problems and muscle pain.