Selenium is a naturally occurring element found in most rocks and soils. It is usually found in combination with sulfide minerals or with silver, copper, lead, and nickel minerals. Although most processed selenium is used in the electronics industry, it is also used as a dietary supplement and in the preparation of pharmaceuticals, in the glass industry, in the making of pigments for plastics, paints, and rubber, as a nutritional additive in the feed of certain livestock, in the making of pesticides and fungicides, and as an ingredient in anti-dandruff shampoo. Radioactive selenium is used in certain medical procedures and diagnostic tests. 

How You Are Exposed

Selenium can be released into the environment by both natural and manufacturing processes. The general population is exposed to low levels of the element in air, food, and water. People working in or living near industries where selenium is produced, processed, or used in the manufacture of commercial products, as well as people living near hazardous waste facilities or coal-burning plants, are at risk for being exposed to higher, harmful levels of selenium.

How Can Radon Affect Your Health?

Selenium has both beneficial and harmful effects. Although small amounts are essential to maintain optimal health, exposure to high levels can cause deleterious effects. Acute oral exposure to high concentrations of selenium can cause nausea, vomiting, and diarrhea. Chronic oral exposure, however, can result in a condition called selenosis. Symptoms include hair loss, nail brittleness, as well as neurological abnormalities (numbness and strange sensations in the extremities).

Breathing in high concentrations of selenium or selenium dioxide can cause irritation in the respiratory tract, bronchitis, difficulty breathing, and stomach pains in the short term. Over the long term, exposure to selenium in the air can cause respiratory irritation, bronchial spasms, and coughing. Exposures to selenium inconcentrations high enough to produce such effects are not usually found outside of the workplace.