Tracing boron: Essential safety levels

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  • Published: Nov 15, 2011
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Tracing boron: Essential safety levels

Tracing boron

Boron is an essential trace element found in many living things but as yet we do not know what the normal levels of this substance are in humans. A study in Chile, where natural boron levels are relatively high, measured exposure levels of boron in drinking water and urine of volunteers using inductively coupled plasma spectroscopy (ICP-OES). The study provides new insights into normality but more importantly offers recommendations for monitoring tap and bottled water supplies to limit exposure.

S. Cortes and C. Ferreccio of the Departamento de Salud Pública, Pontificia Universidad Católica de Chile, Santiago, Chile, E. Reynaga-Delgado of the Centro de Investigaciones Biológicas del Noroeste, La Paz B.C.S., Mexico and A.M. Sancha of the Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Santiago, Chile measured exposure levels of boron in drinking water and urine of volunteers in Arica, an area in the North of Chile with high levels of naturally occurring boron. The team highlights the problems associated with high exposure to boron. High doses of boron, up to 80 mg per kilogram body mass per day in animal models, can cause adverse effects such as anorexia, weight loss, bone disorders and testicular atrophy. There have been no reports of mutagenic or carcinogenic effects in humans for this metalloid element, however. "Little is known about the minimum levels necessary to cause damage to organs or health in humans, thus the urgency of the need to establish a safe range for human populations," the team says.

Naturally boron

According to the World Health Organisation, WHO, "Naturally occurring boron is present in groundwater primarily as a result of leaching from rocks and soils containing borates and borosilicates." It points out that concentrations range from less than 0.3 to more than 100 milligrams per litre across the globe.

The team's ICP-OES data showed that boron concentrations varied in public tap water from 0.22 to 11.3 milligrams per litre. Concentrations of boron in some bottled water samples were much lower at 0.01 mg/l but levels were as high as 12.2 mg/l. All samples were outside the safe limits as recommended by the WHO. The WHO has a provisional limit on boron in drinking water of 0.5 mg/l, provisional, it says, because it might not be achievable with current water treatment technology in areas with very high natural boron levels. The WHO also notes that detection limits are 0.2 micrograms per litre by ICP/MS; and 6 to 10 mg/l with standard ICP/AES.

The team found similarly high levels in urine samples - between 0.45 and 17.4 mg/l. This, they point out, is directly correlated with tap water tested from the homes of the volunteers. The city of Arica is the capital of the eponymous province and is bordered to the North by Peru, to the West by the Pacific Ocean, to the East by Bolivia. Population is approximately 176,000. "The natural sources of water for the city are the Lluta River, which rises in the Andes and flows into the Pacific Ocean, and the wells of the Azapa Valley," the team says, "These two bodies of water are the only source of drinking water for the city." Residents have expressed concerns about the high boron level of their drinking water, hence the various studies commissioned to assess the problem. "This study represents the first detailed assessment of boron exposure in Chile," the team adds and sets a "baseline to establish a safe range for Boron in human populations."

     

Credit: Cortes et al/Elsevier Boron is an essential trace element found in many living things but as yet we do not know what the normal levels of this substance are in humans. A study in Chile, where natural boron levels are relatively high, measured exposure levels of boron in drinking water and urine of volunteers using inductively coupled plasma spectroscopy (ICP-OES).
Boron in Arica, Chile

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