5-[[4-chloro-6-[(3-sulphophenyl)amino]-1,3,5-triazin-2-yl]amino]-4-hydroxy-3-[[4-[[2-(sulphooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2,7-disulphonic acid, sodium salt

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 Red 198, is a solid under all environmental conditions and is highly soluble in water (123 g/L). It is expected to have a low volatility (based on a melting point > 300°C) and it is expected to have a low affinity for soil/sediment (based on the low Log Kow value of < -2.43). 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 it is indicated 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(Mackay et al., 1996a, 1996b; Mackay 1991) 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 substance between four environmental compartments (air, water, soil, sediment) at steady state in a unit world.

Table1. Partitioning modelReactive Red 198

Compartment	Distribution [%]	Half-life [h]
Air	6.78E-7	5.06
Water	0.562	4.32E3
Soil	52.3	8.64E3
Sediment	47.2	3.89E4

It is proposed that although the majority of the substance distributes to the soil/sediment 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.

This assumption is confirmed by the model for the STP Overall Chemical Mass Balance in the US EPA EPI SUITE, which shows that 98% of the influent of the dye is in the water phase:

Table2.STP Overall Chemical Mass Balance

	g/h	mol/h	percent
Influent	1.00E+001	1.1E-002	100.00
Primary sludge	2.50E-002	2.7E-005	0.25
Waste sludge	1.50E-001	1.6E-004	1.50
Primary volatilization	5.35E-018	5.8E-021	0.00
Settling volatilization	1.46E-017	1.6E-020	0.00
Aeration off gas	3.60E-017	3.9E-020	0.00
Primary biodegradation	1.76E-003	1.9E-006	0.02
Settling biodegradation	5.27E-004	5.7E-007	0.01
Aeration biodegradation	6.93E-003	7.6E-006	0.07
Final water effluent	9.82E+000	1.1E-002	98.15
Total removal	1.85E-001	2.0E-004	1.85
Total biodegradation	9.22E-003	1.0E-005	0.09

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.

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, low partition coefficient and fairly rapid hydrolysis rate at environmentally relevant pH’s, 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 mammalian studies therefore in the event of exposure to environmental organisms, effects due to secondary poisoning can be excluded.