Chronic boron toxicity

Health and Safety Factors. Boron trifluoride is primarily a pulmonary irritant. The toxicity of the gas to humans has not been reported (58), but laboratory tests on animals gave results ranging from an increased pneumonitis to death. The TLV is 1 ppm (59,60). Inhalation toxicity studies in rats have shown that exposure to BF at 17 mg/m resulted in renal toxicity, whereas exposure at 6 mg/m did not result in a toxic response (61). Prolonged inhalation produced dental fluorosis (62). High concentrations bum the skin similarly to acids such as HBF and, if the skin is subject to prolonged exposure, the treatment should be the same as for fluoride exposure and hypocalcemia. No chronic effects have been observed in workers exposed to small quantities of the gas at frequent intervals over a period of years. 

Organoboron derivatives, even more than organosilicon compounds, are sensitive to hydrolytic degradation that always leads to the final formation of boric acid. But boric acid has teratogenic properties in chickens. It produces the same malformations as those produced by a riboflavine (vitamin B2) deficiency and the administration of riboflavine prevents these toxic effects. The mechanism by which boric acid produces a deficiency in riboflavine is not known. In man the chronic utilization of boron derivatives results in cases of borism (dry skin, cutaneous eruptions, and gastric troubles). 

Pentaborane is considered to be the most toxic boron hydride in the case of inhalation. Inhalation exposures of small laboratory animals showed values of LDjq of 9 to 46 mg m. It exerts particularly a cumulative action on the central nervous system, accompanied by tremor and cramps. Chronic exposures (for 6 months) to vapours at a concentration of 2.5 mg m resulted in an insufficient oxygen supply to tissues (anoxia), decreases in the body weight, apathy and tremor. Dissection demonstrated no serious pathological changes [77]. The chronic exposures of animals can lea4 to damage to the liver and kidneys [80]. 

Toxicity Boron trifluoride (and organic complexes such as Bp3-etherate) are extremely corrosive substances that are destructive to all tissues of the body. Upon contact with moisture in the skin and other tissues, these compounds react to form hydrofluoric acid and fluoroboiic acid, which cause severe burns. Boron trifluoride gas is extremely irritating to the skin, eyes, and mucous membranes. Inhalation of boron trifluoride can cause severe irritation and burning of the respiratory tract, difficulty breathing, and possibly respiratory failure and death. Exposure of the eyes to BF3 can cause severe burns and blindness. This compound is not considered to have adequate warning properties. Boron trifluoride has not been found to be carcinogenic or to show reproductive or developmental toxicity in humans. Chronic exposure to boron trifluoride gas can cause respiratory irritation and damage. 

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