Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

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Additional information

Sodium perborates were found to be rapidly degraded by bacteria. In addition, the significant decrease of sodium perborate in the ecotoxicity test with the green alga Selenastrum capricornutum (90% elimination after 2 days, Solvay 1993; cf. 6.1.5) shows that not only bacteria are capable to degrade this compound in the aquatic compartment.

There is evidence that microorganisms are able to degrade peroxy-compounds rather quickly with borates, water and oxygen being end products of decomposition. This type of decomposition is expected to depend on the origin, adaption and amount of the microbial population in the tested aquatic medium with removal rates increasing at higher cell numbers.

It has to be noted, however, that the test parameter "decrease of active oxygen" used in degradation studies is only indicative for the biotic or abiotic degradation/decomposition but not for the underlying mechanism. It can be assumed that this degradation is due to the reaction with detoxifying enzymes like catalyse, which is present in nearly all aerobic bacteria as well as in other organisms. In addition the oxygen consumption of the bacteria may shift the equilibrium of sodium perborate in solution towards the degradation products. Here also catalytic reactions with metal compounds may be involved.

No information is available on the degradation of sodium perborate under anaerobic conditions.

From the results of the modified Closed Bottle Test, the degradation by domestic activated sludge and by domestic raw waste water and the elimination experiments in natural river water primary degradation of sodium perborate in industrial and municipal STP as well as in domestic waste water is expected to be rapid. Hence, for the exposure assessment concerning the elimination of sodium perborate in STPs complete biodegradation of the compound is assumed.

Data from a stability test in natural river water as well as from some ecotoxicity tests indicate also primary degradation of sodium perborate emitted directly to surface water, but decomposition here should be significantly slower. From the test on stability in river water a half life of 59 hours can be derived. The degradation rate of sodium perborate and its degradation product hydrogen peroxide is assumed to depend mainly on the density of the natural population present in water and/or the presence of catalytic material (e.g. detoxifying enzymes, transition metals).