Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Reactive Blue FC 75311 displays a low ready biodegradability in that it achieved 0% biodegradation in a 28-day study closed bottle test and was not inherently biodegradable, achieving 0% biodegradation in a modified Zahn-Wellens test. This indicates that the substance is unlikely to achieve a half life of less than 40 or 60 days within fresh water attributed to ready biodegradation alone. 

Abiotic degradation

At pH 9, pH 7 and pH 4 the substance is considered to be degradable abiotically over a period of time according to the EC-guideline utilised. Reactive blue consists of two main compounds. The overall sum of both compounds was determined.

Experimental studies on hydrolytic effects demonstrated that the substance does undergo some hydrolysis at environmentally relevant pH’s, with a half-life of 3, 379, and 34 days at pH 4, 7 and 9, respectively, at 25 °C, based on a pseudo first order rate constant as calculated from the Arrhenius equation.At use conditions during dyeing (pH > 10 at ≥ 60°C) the substance is hydrolytically unstable (t½< 7 hours).As such, degradation is anticipated via this route, albeit slowly. Studies on direct phototransformation in water are not available but it was found that the sulfonated azo dyes can be destroyed by UV photooxidation process (Saliha 2005). The kinetics of the degradation depends on the azo, benzene and naphthalene groups of the dyes. It was found that the first step of the degradation is related to cleavage of azo bond of the molecule and naphthalene ring which leads to further degradation until complete mineralization. It is concluded therefore, that abiotic processes would contribute significantly to the depletion of the substance within the environment.