**2. Boron and boron compounds**

Boron (B) as a metalloid belongs to third group of periodic table. Boron has an interesting unique and complex chemical structure like metal and nonmetal. It has very small atomic size as 4.39cm3 /mol. B includes three valance electrons, and its ionization energy is very high. B's p-orbital includes vacant electron at B+3 state. B has high potential to make anionic complexes than cationic complexes. B occurs in the nature as borates (such as borax Na2B4O7•10H2O), boric acid [B(OH)3 or H3BO3], and BF4 (not very common). In living cells, B occurs in the cytoplasm as H3BO3 and borate forms. Boric acid and borate interact with several different molecules very easily and form different esters and generate mono-, d, poly hydroxyl forms. Boric acid has affinity to furanoid rings of sugars, which are very important for life. These complex compounds are very important during evolution because of providing organisms stability and very strong defense mechanisms.

B's inorganic form is originated from anthropogenic sources in the nature and could found elsewhere in soil, water, and atmosphere. Also it circulates in the air, volcanos, ocean, geothermal water sources, etc. According to EPA (1987), boron compounds are released into the air as anthropogenic sources. Generally, because of boron dust, people are exposed to boron via the air in boron mines. A dose of 14 mg of boron per cubic meter of air has been reported in boron mines where boric acid and refined products are produced. Boron can be found in soil, especially in the form of bonk JMI or borate, absorbed on soil particles, or in soil solution as a free anion. In the research studies, it has been shown that the amount of boron in the plant is primarily related to the soil pH. Other important factors are the plant type, the boron content of the soil, the type of ions that can change in the soil, the amount and type of other minerals in the soil, the amount of organic matter in the soil, the temperature of the soil, the wetting and drying conditions of the soil, the soil-water ratio, the light intensity, and genetic factors. Low-boron soils contain up to 0.7 ppm boron and do not pose a problem for any plant. Medium-boron soils contain 0.7–15 ppm boron, and it has been determined that it does not cause problems for some plants. Soils with high boron contain 15–75 ppm boron and are mostly dangerous for plants, while soils with very high boron contain more than 75 ppm boron, and these are dangerous for plants. Boron has important metabolic functions in plants and plant growth stops in the absence of boron in the soil. Boron shows its effects on drinking water and agricultural water. In 1968, the Water Quality Criteria Committee set the limit value as 1 mg/l; in 1971, as a result of the investigations of the Drinking Water Standards Technical Review Committee, it was decided that there was no evidence to require the 1 mg/l limit, and that 0.3 mg/l was a reliable limit for human health. According to research studies, it is important for human health that drinking water does not contain high levels of boron [14, 15].

The negative effects of boron products on the environment are much lower than in other industrial sectors. In fact, with the effect of radioactive substances after chemotherapy, it is one of the elements that can be considered environmentally friendly due to its necessity for human and living creatures [16].

Depending on the technological developments, the economic grades of the ores are reduced with the development of new methods and equipment, and many stored heaps in the form of waste are evaluated in this way. Accordingly, possible evaluation possibilities in the future should be considered in the disposal of waste. For these reasons, it is necessary to pay maximum attention to the storage of boron wastes. It is possible to list the advantages to be obtained as follows [16].


*Boron and Boron-Containing Compounds Toxicity DOI: http://dx.doi.org/10.5772/intechopen.103179*

Predominant mineral sources of B are found in Australia, China, Turkey, Russia, and Argentina. B and B compounds could not naturally occur as volatile compounds; however, minimal volatile B compounds release to atmosphere via volcanic activities and different industrial places. B is an essential for several body organs and systems, and 1–13 mg/kg consumption is acceptable. High exposure could cause several health disorders in neurological, urogenital, skeleton, and cardiovascular systems [17].
