**Barium CAS Number 7440393**

Barium is a divalent alkaline-earth metal found only in combination with
other elements in nature. The most important of these combinations are
the peroxide, chloride, sulfate, carbonate, nitrate, and chlorate. The
pure metal oxidizes readily and reacts with water emitting hydrogen. The
most likely source of barium in the atmosphere is from industrial
emissions. Barium compounds are used by the oil and gas industries to
make drilling muds. Drilling muds make it easier to drill through rock
by keeping the drill bit lubricated. They are also used to make paint,
bricks, tiles, glass, and rubber. A barium compound (barium sulfate) is
sometimes used by doctors to perform medical tests and to take
barium-rays of the stomach. Since it is usually present as a particulate
form, it can be removed from the atmosphere by wet precipitation and
deposition. Due to the element\'s tendency to form salts with limited
solubility in soil and water, it is expected to have a residence time of
hundreds of years and is not expected to be very mobile. Trace amounts
of barium were found in more than 99% of the surface waters and finished
drinking water samples across the United States.

The soluble salts of barium are toxic in mammalian systems. They are
absorbed rapidly from the gastrointestinal tract and are deposited in
the muscles, lungs, and bone. Inhalation exposure of human populations
to barium-containing dust can result in a benign pneumoconiosis called
\"baritosis.\" At low doses, barium acts as a muscle stimulant and at
higher doses affects the nervous system eventually leading to paralysis.
Acute and subchronic oral doses of barium cause vomiting and diarrhea,
followed by decreased heart rate and elevated blood pressure. Higher
doses result in cardiac irregularities, weakness, tremors, anxiety, and
dyspnea. A drop in serum potassium may account for some of the symptoms.
Death can occur from cardiac and respiratory failure. Acute doses around
0.8 grams can be fatal to humans.

The Department of Health and Human Services, the International Agency
for Research on Cancer, and the Environmental Protection Agency (EPA)
have not classified barium as to its human carcinogenicity.

The following is a presentation of the toxicity information associated
with **Barium**.

**Noncarcinogenic Health Effects**

The Oral Chronic Reference Dose is 7.00E-02 (mg/kg-day).

The Oral Chronic Reference Dose has a modifying factor of 1.

The Oral Chronic Reference Dose has an uncertainty factor of 3.

The Oral Chronic Reference Dose is based on the NTP study from 1994.

The Oral Chronic Reference Dose study critical effect is none observed.

The overall confidence in the Oral Chronic Reference Dose is medium.

The Inhalation Chronic Reference Concentration is 5.00E-04 (mg/m^3^).

The Inhalation Chronic Reference Concentration has a modifying factor of
1.

The Inhalation Chronic Reference Concentration has an uncertainty factor
of 1000.

The Inhalation Chronic Reference Concentration is based on the U.S. EPA
study from 1984.

The Inhalation Chronic Reference Concentration study target organ is
fetus.

The Inhalation Chronic Reference Concentration study critical effect is
fetotoxicity.

The Dermal Chronic Reference Dose is 4.90E-03 (mg/kg-day).

The Dermal Chronic Reference Dose is based on a gastrointestinal
absorption factor of 0.0700.