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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Experimental data show that cetrimonium bromide is readily biodegradable under conditions where cetrimonium bromide does not exert toxicity to the microorganisms.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Experimental data show that cetrimonium bromide is readily biodegradable, at conditions where the substance does not exert toxicity to the microorganisms.

In a weight of evidence approach, data on cetrimonium chloride are included to support the data on biodegradability of cetrimonium bromide. Read across between homologues of this type of substances can be done, as the degradability is determined by the alkyl structure and not by the counterion. Therefore the degradability of cetrimonium chloride is considered to represent that of cetrimonium bromide.

Studies on cetrimonium chloride indicate that the substance is biodegradable, but not necessarily passing the criteria for readily biodegradability (FeF, 1993; Madsen et al, 2001; van Ginkel, 1996). This is especially observed when tested in concentrations above a certain level approximately 10-20 mg/L, which is considered to have a toxic effect on the microorganisms in the test system. When toxicity has been removed by the addition of silica gel or SIO2 to the test system, cetrimonium chloride has proven to pass the criteria for readily biodegradability (van Ginkel, 2004; OECD, 1996). When silica or SiO2 particles are present in the test system, the substance will enter equilibrium between adsorbed and dissolved phase. When the dissolved part of the substance biodegrades, the substance is gradually released from the adsorbed phase, and a low concentration not exerting toxicity is maintained in the test system.

Supporting studies with cetrimonium bromide show that cetrimonium bromide is biodegradable at concentration of 10-25 mg/L (Dean-Raymond & Alexander, 1977) and passed the criteria for ready biodegradation at 5 mg/L (Garcia et al, 2001). Note on the weight of evidence approach taken on the biodegradability of cetrimonium bromide is attached the endpoint summary.