Boron in Water
Boron occurs as sodium borate (borax) or as calcium borate (colemanite), in mineral deposits and in natural waters. It is never found in nature in its elemental form. Boron is usually found in low concentrations in surface waters and is usually present around igneous rock formations. Boron is an essential element for growth of plants, but there is little evidence that boron is required by animals. Therefore, boron in drinking water is not generally regarded as a hazard to human beings.
Boric acid can be toxic to fresh water fish, however, the reported concentrations are quite high. The effect of boric acid and sodium borate in highly turbid waters on the mosquito fish was tested with the following results.
Concentration in Mg/L TLM
Chemical Temperature Range pH Range 24 Hr 48 Hr 96 Hr T
Boric Acid 20/23° C 5.4/7.3 18,000 10,500 5,600
Sodium Borate 22/26° C 8.6/9.1 12,000 8,200 3,600