Barium is a chemical element with symbol Ba and atomic number 56. It is a silvery-white metal that can be found in the environment, where it exists naturally. Because of its high chemical reactivity barium is never found in nature as a free element. It occurs combined with other chemicals, such as sulphur, carbon or oxygen. Barium is very light and its density is half that of iron. It oxidises in air, reacts vigorously with water to form the hydroxide, liberating hydrogen. Barium reacts with almost all the non-metals, often forming poisonous compounds. This substance does not occur as a mineral, but can be prepared by heating barium carbonate. [1,2]
Barium is often used in barium-nickel alloys for spark-plug electrodes and in vacuum tubes as a drying and oxygen-removing agent. In addition, it is used in fluorescent lamps: impure barium sulphide phosphoresces after exposure to the light. Barium compounds are used by the oil and gas industries to make drilling mud. Drilling mud simplifies drilling through rocks by lubricating the drill. Furthermore, barium compounds are used to make paint, bricks, tiles, glass, and rubber. Barium nitrate and clorate give fireworks a green colour.
In the Environment 
- Barium enters the environment naturally through the weathering of rocks and minerals. Anthropogenic releases are primarily associated with industrial processes.
- In the atmosphere, barium is likely to present in particulate form and is primarily removed by wet and dry deposition.
- In aquatic media, barium is likely to precipitate out of solution as an insoluble salt.
- Barium is not very mobile in most soil systems due to the formation of water-insoluble salts and the inability of barium to form soluble complexes with fulvic and humic acids.
- Barium has the potential to bioconcentrate in marine animals and plants and in some terrestrial plants such as legumes, forage plants, Brazil nuts, and mushrooms.
Sources & Routes of Exposure 
Sources of Exposure
- The general population is exposed to barium through consumption of drinking water and food, usually at low levels.
- Exposure may also occur during x-ray diagnosis. Barium sulphate is frequently utilised as a benign, radiopaque aid to x-ray diagnosis in colorectal and some upper gastrointestinal examinations.
- Exposure to barium and compounds may also occur via contact with oil and gas drilling muds, automotive paints, stabilisers for plastics, case hardening steels, bricks, tiles, lubricating oils, and jet fuel as well as in various types of pesticides.
- Occupational exposure to barium primarily occurs in barium mining or processing industries.
Routes of Exposure
- Inhalation – generally limited to occupational exposure.
- Oral – Primary route of exposure for general population. Some foods, such as Brazil nuts, seaweed, fish, and certain plants, may contain high amounts of barium.
- Dermal – minor route of exposure.
Health Effects 
Barium has been found to potentially cause gastrointestinal disturbances and muscular weakness when people are exposed to it at levels above the EPA drinking water standards for relatively short periods of time. Some people who eat or drink amounts of barium above background levels found in food and water for a short period may experience vomiting, abdominal cramps, diarrhoea, difficulties in breathing, increased or decreased blood pressure, numbness around the face, and muscle weakness. Eating or drinking very large amounts of barium compounds that easily dissolve can cause changes in heart rhythm or paralysis and possibly death.
Animals that drank barium over long periods had damage to the kidneys, decreases in body weight, and some died.
The Department of Health and Human Services (DHHS) and the International Agency for Research on Cancer (IARC) have not classified barium as to its carcinogenicity. The EPA has determined that barium is not likely to be carcinogenic to humans following ingestion and that there is insufficient information to determine whether it will be carcinogenic to humans following inhalation exposure.
First Aid Measures
- Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Warm water must be used. Get medical attention.
- Skin Contact: In case of contact, immediately flush skin with plenty of water. Cover the irritated skin with an emollient. Remove contaminated clothing and shoes. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention.
- Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
- Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention.
- Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
- Ingestion: Do NOT induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. If large quantities of this material are swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie, belt or waistband.
Exposure Controls & Personal Protection
Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.
The following personal protective equipment is recommended when handling barium:
- Splash goggles;
- Lab coat;
- Dust respirator (be sure to use an approved/certified respirator or equivalent);
Personal Protection in Case of a Large Spill:
- Splash goggles;
- Full suit;
- Dust respirator;
- A self-contained breathing apparatus should be used to avoid inhalation of the product.
Note: Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling.
- EPA has set a limit of 2.0 milligrams of barium per litre of drinking water (2.0 mg/L), which is the same as 2 ppm.
- Occupational Safety and Health Administration (OSHA) has set Permissible Exposure Limits (PELs) of 0.5 milligrams of soluble barium compounds per cubic metre of workplace air (0.5 mg/m3) for 8-hour shifts and 40-hour work weeks. The OSHA limits for barium sulphate dust are 15 mg/m3 of total dust and 5 mg/m3 for respirable fraction.
- The National Institute for Occupational Safety and Health (NIOSH) has set Recommended Exposure Limits (RELs) of 0.5 mg/m3 for soluble barium compounds. The NIOSH has set RELs of 10 mg/m3 (total dust) for barium sulphate and 5 mg/m3 (respirable fraction).
- Safe Work Australia has set a TWA exposure limit for barium sulphate of 10 mg/m3
- Safe Work Australia has set a TWA exposure limit for barium, soluble compounds of 0.5 mg/m3