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Environmental fate & pathways

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Reactive Blue 250 has a very high water solubility. Screening tests for biodegradation of the structural analogue Reactive Black 5 in water or under environmental conditions showed that the test substance is not readily biodegradable. However, it is rapidly hydrolysed with a half-life of 1 to 2 days at pH 7. When Reactive Black 5 was applied to a sediment/water test system at a final concentration of 1 mg/kg in the test system, the test substance was rapidly degraded to Reactive Black 5 bis-vinyl and further to Reactive Black 5-OH. The DT50 of Reactive Black 5-ester was 2 days. After 3 to 6 days, only 10% of the applied Reactive Black 5 could be found. All metabolites decreased at the end of the test period to levels around the lower level of quantification. Consequently, an accumulation of metabolites could be excluded. The majority of the metabolites of Reactive Black 5 were deposited in form of non-extractable residues in sediment during test phase. After about 1 month, mineralization of the metabolites started.

A bioaccumulation study in the carp revealed bioconcentration factors < 11 for 0.2 mg/L and < 1.1 for 2 mg/L. Hence, Reactive Black 5 either as bis-ester, or as bis-vinyl does not bioaccumulate in the aquatic compartment. Based on data from kinetic and metabolism studies in rats (oral and intravenous administration), the test item Reactive Black 5 as well as its structural analogue Reactive Blue 250 does not have any bioaccumulation potential in animals. Due to the very low toxicity, rapid degradation and lack of bioaccumulative properties, secondary poisoning can be excluded for both items.