Benzenesulfonic acid, 4-(acetylamino)-2-amino-5-[2-[3-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]diazenyl]-, sodium salt (1:2)

Endpoint summary

Additional information

Environmental Fate

It should be noted that the test substance is not considered as posing a hazard to the aquatic environment.

The test substance, Reactive Orange 107, is a solid under all environmental conditions and is highly soluble in water. It has a low volatility (based on the high melting / boiling point and high molecular weight) and a low affinity for soil / sediment (based on the partition coefficient value of Log Kow -4.5). As such, any environmental release will result in virtually all of the substance compartmentalising into water compartments, with little release directly to atmosphere or compartmentalising to soil/sediment compartments.

Any potential exposure to the environment is predicted to result in rapid redistribution to water; due to its low volatility, high water solubility and partitioning values indicates that the majority of the substance would eventually partition to water rather than to soil and sediment should it be released to the environment. 

A Level III fugacity model was conducted in the US EPA EPISUITE which assumes steady-state but not equilibrium conditions.The Level III model in EPI Suite predicts partitioning between air, soil, sediment and water using a combination of default parameters and various input parameters.This model has been used to calculate the theoretical distribution of the highest % component substance between four environmental compartments (air, water, soil, sediment) at steady state in a unit world.

Partitioning is detailed to be:

-Air                 3.96E-9%

-Water          36.9%

-Soil              63%

-Sediment       0.0974%

It is proposed that although the majority of the substance distributes to the water and soil compartments within the model, the high solubility in water indicates that the substance is more likely to distribute to water – e.g. soil pore water. Reactive Orange 107 displays a low ready biodegradability in that it achieved < 10% biodegradation in a 56-day test for ultimate biodegradability of organic compounds (ISO 11734) and was not inherently biodegradable, achieving 0% biodegradation in a Zahn-Wellens test. Evaluation for elimination via adsorption showed that ca 30% of the dye adsorbs to activated sludge. Elimination of the dyestuff via flocculation with iron-oxides showed an 80% reduction of Reactive Orange 107.

The substance is expected to hydrolyse under normal environmental conditions. Experimental studies on hydrolytic effects of a structural analogue demonstrated that the substance does undergo rapid hydrolysis at environmentally relevant pH’s, (t1/2 = 87 hours at pH7 and 1 hour at pH9), indicating the potential for significant removal by hydrolysis. At use conditions during dyeing (pH > 10 at ≥ 60°C) the substance is hydrolytically unstable; from the hydrolysis study conducted on the read-across substance, decomposition at pH 9 was demonstrated as 17 min at 37°C. As such, degradation is anticipated via this route. Studies on direct phototransformation in water are not available but it is assumed on the basis of chemical structure and nature of use that the substance is not degraded by direct photolysis. It is concluded, therefore, that abiotic processes would contribute significantly to the depletion of the substance within the environment.

Reactive Orange 107 has an estimated log Kow of -4.52. 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 pH’s, it can be concluded that it is unlikely that Reactive Orange 107 could potentially be persistent within the environment.

Adsorption to soil is deemed to be low, based on the very low partition coefficient value and high water solubility. Such a low potential indicates that the substance is unlikely to bind tightly to soils and sediments and instead partition almost exclusively to water. As such, significant exposure related effects to sediment and soil dwelling organisms are considered to be negligible.

Based on its high water solubility and low partition coefficient it can be concluded that it is unlikely that Reactive Orange 107 could potentially be persistent within the environment in its registered form. 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 Orange 107 demonstrates low acute toxicity in mammalian studies therefore in the event of exposure to environmental organisms, effects due to secondary poisoning can be excluded.

Justification for classification or non classification

The above results triggered no classification under the Dangerous Substance Directive (67/548/EEC) and the CLP Regulation (EC No 1272/2008).