Bromine (Br) is a chemical element classified as a halogen, positioned between chlorine and iodine on the periodic table. At standard room temperature, it exists as a dense, reddish-brown liquid that readily evaporates into a reddish-brown vapor. This vapor is known for its strong, pungent odor. Bromine is highly reactive, preventing it from being found in its pure, elemental form in nature. Instead, it naturally occurs as compounds with other elements, known as bromides. These water-soluble bromide salts are distributed throughout the environment and are used widely in industrial and consumer products.
Bromine’s Presence in the Natural Environment
The vast majority of natural bromine is concentrated in the world’s oceans due to the high solubility of bromide salts. Seawater typically holds a concentration of about 65 parts per million of bromine, serving as the largest natural reservoir for the element.
Natural salt deposits and subterranean brine wells represent ancient, concentrated sources of bromide formed as prehistoric seas evaporated. For example, the Dead Sea is exceptionally rich in bromine, and these concentrated brines are a primary source for industrial production.
Bromine is also naturally absorbed and concentrated by certain life forms, particularly in marine ecosystems. Some species of sea algae and other marine organisms actively accumulate bromide. Terrestrial plants and animals also contain trace amounts of bromide, demonstrating its widespread presence across the biosphere.
Industrial and Chemical Applications
Bromine compounds are fundamental chemical intermediates in large-scale industrial processes. In the oil and gas industry, dense solutions of calcium bromide and zinc bromide, known as “clear brines,” are used as drilling and completion fluids. These heavy fluids help control pressure in deep wells and stabilize the bore hole.
Agricultural practices have historically relied on bromine compounds, primarily methyl bromide (bromomethane), as a fumigant for soil and stored commodities. This application was effective for pest control, but international agreements have led to a significant phase-out of its use due to its potential to deplete the stratospheric ozone layer.
Bromine is also utilized in water sanitation as an alternative to chlorine, especially in closed systems like swimming pools and industrial cooling towers. Compounds such as bromochlorodimethylhydantoin (BCDMH) function as biocides, effectively killing bacteria and algae to maintain water quality. The element also plays a role in specialized manufacturing, including its use in the production of certain catalysts and in the form of silver bromide for traditional photographic film and paper.
Common Bromine-Containing Consumer Products
Brominated Flame Retardants (BFRs) are the most widely encountered use of bromine compounds in consumer goods, where they are added to plastics and textiles to meet fire safety standards. These compounds work by interfering with the chemical reactions that occur during combustion, slowing the spread of fire. They are commonly incorporated into the plastic casings of electronics, the circuit boards within computers and televisions, and in the foam and fabric of upholstered furniture.
Specific BFRs like Tetrabromobisphenol A (TBBPA) are often chemically bonded into printed circuit boards. Others, such as Polybrominated Diphenyl Ethers (PBDEs), were historically added loosely to plastics and foams. The presence of these additives in house dust and the environment has led to regulatory actions restricting the use of some BFR types.
Bromine compounds have also appeared in food products, though their use is increasingly restricted. Brominated Vegetable Oil (BVO) was historically added to citrus-flavored soft drinks and beverages. BVO functions as an emulsifier, preventing the fruit flavoring from separating and floating to the surface during storage. Due to health concerns, the U.S. Food and Drug Administration (FDA) has revoked the regulation permitting its use.
Potassium bromate is another compound sometimes used as a dough conditioner in the production of baked goods, acting as a flour treatment agent. Furthermore, bromide salts are found in certain pharmaceuticals, where they may be used in anti-epileptic medications or topical antiseptics. Certain synthetic dyes used to color plastics and fabrics also contain bromine atoms as part of their chemical structure.