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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Reactive Red 198 displayed low biodegradability (< 20%) in an ultimate biodegradability test. This indicates that it is unlikely to achieve a half-life of less than 40 or 60 days within fresh water or marine water, respectively, attributed to ready biodegradation alone. The substance undergoes hydrolysis at environmentally relevant pH’s (extrapolated half-lifes at 25°C are 6 days at pH 7 and < 1 day at pH 9). 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 et al. (2005)). The kinetics of the degradation depends on the azo, benzene and naphthalene groups of the dyes. The first step of the degradation is related to cleavage of the 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.

Reactive Red 198 has a measured log Kow of < -2.43. This value indicates that possible bioaccumulation in the food chain is not anticipated. Given the fact that the substance is subject to hydrolysis at biologically relevant pH’s, it is anticipated that bioaccumulation of the substance itself would not occur, as hydrolytic effects in association with metabolic effects would result in removal of the substance.

Based on its high water solubility, low partition coefficient and fairly rapid hydrolysis rate at environmentally relevant pHs, it can be concluded that it is unlikely that Reactive Red 198 could potentially be persistent within the environment. Abiotic effects within the environment will result in eventual removal from the environment and hence significant contact with the organisms in the food chain can considered to be minimised.

Finally, Reactive Red 198 demonstrates low acute toxicity in aquatic and mammalian studies therefore in the event of exposure to environmental organisms, effects due to secondary poisoning can be excluded.