Boron

doi:10.1515/ci.1999.21.2.50a

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Boron

Published/Copyright: September 1, 2009

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From the journal Chemistry International -- Newsmagazine for IUPAC Volume 21 Issue 2

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New Books and Publications

New Publication from the World Health Organization

Boron

Environmental Health Criteria, No. 204 1998, xviii + 201 pages (English with summaries in French and Spanish), ISBN 92 4 157204 3, CHF 42.-/USD 37.80; In developing countries: CHF 29.40. Order no. 1160204

This book evaluates the risks to human health and the environment posed by boron, a naturally occurring element widely distributed, in the form of various inorganic borates, in the oceans, sedimentary rocks, coal, shale, and some soils. Boron is also used in laundry bleach and in the manufacture of glass, glass products, fertilizers and herbicides, antiseptics, and pharmaceuticals. Because boron is widely detected in drinking water and occurs naturally in fruits, nuts, and vegetables, the report gives particular attention to health risks associated with exposure of the general population through diet and drinking water.

A section on sources of human and environmental exposure cites evidence that boron enters the environment mainly through volatilization from seawater, volcanoes, geothermal steam, and natural weathering of clay-rich sedimentary rock. Although industrial uses account for much smaller releases, the report notes that all of the boron from the sodium perborate contained in detergents ultimately enters the wastewater system, and is not removed by standard water treatment procedures.

The environmental behavior of boron is covered in the next section, which concludes that boron does not persist in the atmosphere to a significant degree, adsorbs onto soil particles, accumulates in aquatic and terrestrial plants, but does not magnify through the food chain. Numerous findings indicate that boron is an essential micronutrient for higher plants. A section on environmental levels and human exposure cites diet and drinking water as the principal sources of exposure for the general population. Occupational exposure to boron compounds is judged to be potentially significant, with inhalation of dusts singled out as the most significant route of exposure. Concerning kinetics and metabolism in laboratory animals and humans, numerous studies demonstrate that boric acid and borax are readily absorbed from the gastrointestinal and respiratory tracts, widely distributed, and rapidly excreted in urine.

The most extensive section reviews findings from toxicity studies in laboratory mammals and test systems. General clinical signs of exposure are described as depression, ataxia, occasional convulsions, decreased body temperature, and violet red color of skin and mucous membranes. The review found unequivocal evidence that the male reproductive tract is the principal target of toxicity. The review also cites several recent reports indicating that boron in physiological amounts is beneficial to, if not essential for, higher animals.

An evaluation of the few human studies of toxicity concludes that exposure is associated with short-term and reversible irritant effects on the upper respiratory tract, nasopharynx, and eye. The most frequently observed symptoms involve the gastrointestinal tract and include vomiting, abdominal pain, diarrhea, and nausea. Less frequently observed symptoms include lethargy, rash, headache, light-headedness, fever, irritability, and muscle cramps. Data on carcinogenicity were judged inadequate for evaluation. In line with findings from animal studies, the review found several recent studies demonstrating that boron is a dynamic trace element that can affect the metabolism or utilization of numerous substances essential to life processes.

On the basis of all evidence considered, the report established a tolerable intake for boron of 0.4 mg/ kg body weight per day.

Published Online: 2009-09-01

Published in Print: 1999-03

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https://doi.org/10.1515/ci.1999.21.2.50a