Boron trifluoride

Endpoint summary

Additional information

When released in the atmosphere boron trifluoride (BF3), which is a strong Lewis' acid, forms in contact with atmospheric moisture the complex: dihydrated boron trifluoride (BF3, 2H2O). On the opposite if BF3 is directly brought into contact with water, it reacts violently. That is the reason why all the assessment of environmental fate and pathways is based on the properties of the more stable dihydrated form of boron trifluoride.

Measurement of fluoride ion production over a range of pH values (1.2 to 9), using both ion chromatography and an ion-selective electrode, indicated a hydrolytic half-life time of less than 30 minutes for boron trifluoride. Subsequent analysis of boric acid by titration confirmed the rapidity of the reaction. Consequently, the risk associated to dehydrated boron trifluoride when release into water can be assessed based upon the hazards of its breakdown products in water: boric acid and fluoboric acid The EU Risk assessment report on Hydrofluoric acid indicates for fluoride ions, which are one of the hydrolysis products, a NOEC of 0.9 mg/L (or 3.3 mg/L derived with SSD). Therefore, it can be assumed that the toxicity of BF3 is dominated by the toxicity of H3BO3 (NOEC of 0.56 mg/L (or 1.9 mg/L derived with SSD). For this reason the aquatic hazard assessment of BF3 is based on the several data obtained for boric acid , which are fully described and discussed in the EU RAR.

Hydrolysis is also the the most relevant process for the soil compartment. BF3 2H2O formed in moisture air may transfer into soil via dry and/or wet deposition, where in turn, it will undergo hydrolysis in high moistured soils and in pore water. In addition, the sorption potential of boron on soils was widely described and assessed as low (European Risk Assessment of Boric acid, 2007).

Based on the uses inventoried for boron trifluoride, no direct application of the substance on the soil compartment is expected. The environmental risk of borates were evaluated by considering exposures resulting from wastewater entering rivers or being used for irrigation and from sewage sludge being applied to agricultural soil (Human and Environmental Risk Assessment on ingredients of Household Cleaning Products relative to boric acid, 2005). No significant risks were identified. The concentrations of borates entering the terrestrial environment would be less than results from agricultural application of borates as plant micro-nutrients. Use of wastewaters for irrigation is presently subject to limitation based on total salinity and from use of perborates; the use of boric acid and borax in liquid detergent applications would not result in unacceptable concentrations.

All that together supports the fact that the exposure of the terrestrial compartment to BF3 can be considered negligible and that the potential hazards associated to this exposition doesn’t involve a risk for the terrestrial organisms.