Boron is a solid substance that widely occurs in nature. It usually does not occur alone, but is often found in the environment combined with other substances to form compounds called borates. Common borate compounds include boric acid, salts of borates, and boron oxide. Boron and salts of borate have been found at hazardous waste sites. Boron alone does not dissolve in water nor does it evaporate easily, but it does stick to soil particles. No information was found on whether common forms of boron evaporate easily or stick to soil particles; however, these forms do dissolve in water.
Boron is present in air, water, and soil, but no information is available on how long it remains in these media. There is also no information available on the occurrence of borates in the environment or on how long they persist in the environment.
Borates are used mostly in the production of glass. They are also used in fire retardants, leather tanning and finishing industries, cosmetics, photographic materials, with certain metals, and for high-energy fuel. Pesticides for cockroach control and wood preservatives also contain borates.
Exposure to boron
Boron occurs mainly in the environment through release into air, water, or soil after natural weathering processes. It can also be released from glass manufacturing, coal-burning power plants, copper smelters, and through its use in agricultural fertilizer and pesticides. It is estimated that releases from these sources are less than through natural weathering processes.
You can be exposed to boron in food (mainly vegetables and fruits), water, air, and consumer products. Infants, in particular, can be exposed to borates in products used to control cockroaches. Since boron is taken up from the soil by plants, it can enter the food chain. Although boron has been found in animal tissue, it does not accumulate and it is not likely that eating fish or meat will increase the boron levels in your body. Boron has been found in groundwater at very low levels. Background levels of boron up to 5 parts of boron in 1 million parts (ppm) of surface water have been reported. However, in dry areas where there are natural boron-rich deposits, boron concentrations can be as high as 360 ppm.
No data were found on the occurrence of boron compounds in surface or groundwater. While current drinking water surveys do not report any levels of boron, it has been found in tap water in the past. Levels reported in drinking water were less than 1–3 ppm. There is potential for exposure to boron through contact with soil, since boron sticks to soil particles.
Background levels up to 300 ppm have been reported. Exposure to air contaminated with boron is not likely to occur in the general population; however, there is risk of exposure to borate dust in the workplace. Concentrations from 1–14 milligrams of boron dust per cubic meter of air (mg/m³) have been reported in borax mining and refining plants and at sites where boric acid is manufactured. Exposure to boron may also occur from the use of consumer products, including cosmetics, topical medical preparations, and some laundry products. The average daily boron intake has been estimated to be 10–25 mg.
Pathways for boron in the body
Boron can enter your body when you eat food (fruit and vegetables) breathe borate dust in the air, and when damaged skin comes in contact with it. Because very small amounts of boron are present in all drinking water, boron can enter your body when you drink water. When boron enters the body by mouth or when you breathe borate dust, it goes to the intestines where it is passed to various parts of the body including the liver, brain, and kidney.
No information is available on what factors affect how fast boron enters the body. However, animal studies suggest boron readily enters the body after contact with damaged skin. Most of the boron leaves the body in urine primarily from food eaten. Over half of the boron taken by mouth can be found in urine within 24 hours and the other half can be detected for up to 4 days. Boron compounds can be found in urine up to 23 days if you are accidentally exposed to very large amounts.
Health effects of boron
If humans eat large amounts of boron (4,161 ppm) over short periods of time, it can affect the stomach, intestines, liver, kidney, and brain and can eventually lead to death. Irritation of the nose and throat or eyes can occur if small amounts of boron (4.1 mg/m³) are breathed in. Boron can irritate the eyes if it comes in contact with them for long periods of time.
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
Animal studies indicate that the male reproductive organs, especially the testes, are affected if large amounts of boron are eaten or drunk for short or long periods of time. Studies in animals also indicate delayed development and structural defects in offspring, primarily in the rib cage, from maternal exposure to boron during pregnancy. These effects have not been seen in humans. Irritation of the nose can occur in animals if large amounts of boron are breathed in for long periods of time. These effects have not been seen in humans. No information is available on whether boron is likely to cause cancer in humans. There is no evidence of cancer in animals exposed to boron for long periods of time.
Medical tests for exposure to boron
There are reliable and accurate ways of measuring boron in the body. Blood and urine can be examined to determine if excessive exposure to boron has occurred. Boron and, to a limited extent, boron-related compounds can be measured in body fluids. However, special equipment is needed for detection and analysis. Tests are not routinely available in a doctor's office. It is not known whether boron levels measured in the body can be used to predict potential health effects.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Agency for Toxic Substances and Disease Registry. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Agency for Toxic Substances and Disease Registry should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.