Perboric acid, sodium salt

Ecotoxicological Summary

Additional information

As a consequence of the decomposition behaviour of sodium perborate in aqueous solution and having in mind the analytical problems concerning the determination of perborates in water the results of laboratory tests on aquatic toxicity of sodium perborate do not allow conclusions on the nature of the substance or degradation products, to which the test species were exposed. The primary degradation product of sodium perborate in aqueous solution is boric acid. Furthermore exposure to hydrogen peroxide may occur as sodium perborate is in aqueous solutions in equilibrium with this substance (cf. 5.1.2). Concerning this exposure most aquatic organisms have developed detoxifying mechanisms to prevent cell damage. Antioxidant enzyme systems containing catalase decompose reactive oxygen species stepwise to water. More information on the ecotoxic effects of hydrogen peroxide can be found in the EU-Risk Assessment Report for this compound (ECB 2003). After degradation of hydrogen peroxide the remaining borate species should be the sole toxicologically relevant substances with sodium metaborate being the first degradation product. The most important borate species which will be present in aqueous media under environmental conditions should be boric acid (H₃BO₃). The ecotoxicity of boric acid has been reviewed in ECB (2009).

In ECB (2009), the PNEC for aquatic organisms for boron was derived based on added concentrations, in order to take both naturally and anthropogenic sources of boron into account. For practical reasons boric acid and other borates are usually expressed on the basis of boron. The PNEC_add,aquatic for freshwater systems was set to 0.18 mg B/L. For microorganisms STPs, a PNEC_add,STP of 1.8 mg B/L was calculated. The assessment for sediments was based on the equilibrium partitioning method, therefore no further risk assessment was performed. The PNEC_{add,terrestrial} was set to 0.4 mg B/kg dwt soil, the value being based on toxicity tests on terrestrial organisms.

For hydrogen peroxide, the PNEC was calculated based on added concentrations i.e. background concentrations have been excluded (ECB 2003). The PNEC_aquatic was determined to be 10 μg/l and the PNEC_{microorganisms} to be 4.66 mg/l. For sediments and the terrestrial compartment, the PNECs were based on the equilibrium partitioning method, therefore no further risk assessment was performed.