Boron

2. Where is boron found?

• 2.1 What is the production and use of boron?
• 2.2 What are the sources of boron releases to the environment?
• 2.3 How does boron react in the environment?

2.1 What is the production and use of boron?

The source document for this Digest states:

Production, uses, environmental fate, and sources of exposure

Economic borate deposits are rare, occurring in arid regions of Turkey, the USA, Argentina, Chile, Russia, China, and Peru. Total world production of boron minerals -- mainly colemanite, ulexite, tincal, and kernite -- was approximately 2 750 000 tonnes in 1994. About 800 000 tonnes of commercial borate products, expressed as B²O³, were manufactured from the boron minerals.

Major end uses for borate include insulation- and textile-grade fibreglass, laundry bleach (sodium perborate), borosilicate glass, fire retardants, agricultural fertilizers and herbicides (as a trace element), and enamels, frits, and ceramic glazes, as well as a myriad of miscellaneous applications.

Source & ©: IPCS "Environmental Health Criteria (EHC) 204 ",
Summary of the Report, Chapter 1.1.2
For more information, see the full IPCS document
Sources of Human and Environmental Exposure , Chapter 3

2.2 What are the sources of boron releases to the environment?

The source document for this Digest states:

Boron enters the environment mainly through the weathering of rocks, boric acid volatilization from seawater, and volcanic activity. Boron is also released from anthropogenic sources to a lesser extent. Anthropogenic sources include agricultural, refuse, and fuel wood burning, power generation using coal and oil, glass product manufacture, use of borates/perborates in the home and industry, borate mining/processing, leaching of treated wood/paper, and sewage/sludge disposal. Many of these sources are difficult to quantify.

Atmospheric emissions of borates and boric acid in particulate and vapour form occur as a result of volatilization from the sea, volcanic activity, and, to a lesser extent, mining operations, glass and ceramics manufacturing, the application of agricultural chemicals, and coal-fired power plants. Boron is not present in the atmosphere at significant levels; however, the total amount present in the atmosphere at any one time is significant owing to the huge volume of the atmosphere. Based on their water solubility, borates would not be expected to persist to a significant degree in the atmosphere.

Boron can be released into water and soil water through weathering processes and, to a much smaller extent, through anthropogenic discharges such as sewage outfalls.

Source & ©: IPCS "Environmental Health Criteria (EHC) 204 ",
Summary of the Report, Chapter 1.1.2
For more information, see the full IPCS document
Sources of Human and Environmental Exposure , Chapter 3

2.3 How does boron react in the environment?

The source document for this Digest states:

Adsorption-desorption reactions are expected to be the only significant mechanism influencing the fate of boron in water. The extent of boron adsorption depends on the pH of the water and the concentration of boron in solution.

Boron is adsorbed onto soil particles, with the degree of adsorption depending on the type of soil, pH, salinity, organic matter content, iron and aluminium oxide content, iron- and aluminium-hydroxy content, and clay content. Boron adsorption can vary from being fully reversible to irreversible, depending on the soil type and condition.

Borate ions present in aqueous solution are essentially in their fully oxidized state. No aerobic processes are likely to affect their speciation, and no biotransformation processes are reported. Therefore, there are unlikely to be any differences in boron species due to biotransformation.

The octanol/water partition coefficient of boric acid has been measured as 0.175, indicating a low bioaccumulation potential. Laboratory experiments with aquatic organisms have confirmed this potential. Plants accumulate boron; however, uptake is affected by the pH of the soil solution, temperature, light intensity, and the concentration of other elements (e.g. calcium and potassium). The results of studies of boron accumulation in plants, insects, and fish have shown that boron bioaccumulates in plants but does not biomagnify in aquatic food-chains.

Source & ©: IPCS "Environmental Health Criteria (EHC) 204 ",
Summary of the Report, Chapter 1.1.2
For more information, see the full IPCS document
Environmental Transport, Distribution and Transformation , Chapter 4