Barium is a chemical element classified among the alkaline earth metals. It has a number of uses, from fireworks to medicine, usually in the form of barium compounds such as barium sulfate. Many of these forms of toxic, leading workers who interact with barium to use extreme care when they handle this element. Consumers are probably most familiar with barium in the form of barium sulfate, used in liquid suspensions for x-ray diagnostics.

In nature, barium is not found in a pure state because it interacts readily with air. When isolated, the element takes the form of a soft silvery white metal, although it will quickly oxidize when exposed to air. In the Earth's crust, barium is about the 18th element in order of abundance, and it is found in a number of naturally occurring compounds. On the periodic table of elements, barium is identified with the symbol Ba, and it has an atomic number of 56.

The existence of this reactive metal was known for at least a century before Sir Humphrey Davy succeeded in isolating it in 1808. The name of the element is derived from the Greek word for “heavy,” a reference to the element's high specific gravity. After Davy's discovery, a number of uses for barium were explored, and several companies specialize in the mining and processing of barium and natural compounds of the element. Barium sulfate and barium carbonate are two common barium compounds.

In fireworks, barium nitrate is used to turn the explosives green. Compounds of the element are also used in electrodes, pigments, batteries, semiconductors, and glass making. In the oil industry, barium is used as a weight in wells, and barium carbonate is sometimes used as rodent poison. In the hospital environment, patients drink barium for x-ray imaging because it is opaque to x-rays, allowing doctors to see the condition of the esophagus, stomach, and intestinal tract.

Barium poisoning can cause muscle weakness, kidney damage, and nervous system problems. Fortunately, the metal does not bioaccumulate, so once the symptoms of barium poisoning are recognized, the condition can be treated and the metal will work its way out of the victim's body. People are at risk for barium poisoning through both inhalation and ingestion, and it is typically found in industrial environments where workers handle high volumes of barium. Barium can also poison water supplies, although routine testing of a water supply should catch this, along with other forms of contamination.