1,5-Naphthalenedisulfonic acid, 2-[2-[8-[[4-chloro-6-[[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]amino]-1,3,5-triazin-2-yl]amino]-1-hydroxy-3,6-disulfo-2-naphthalenyl]diazenyl]-, sodium salt (1:5)

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 239, is a solid under all environmental conditions and is highly soluble in water (299 g/L). It is expected to have a low volatility (based on a melting point > 320°C) and it is expected to have a low affinity for soil/sediment (based on the low log Kow value of < -2). 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.

Table 1. Partitioning model Reactive Red 239

Compartment	Distribution [%]	Half-life [h]
Air	4.78E-4	3.41
Water	0.553	4.32E3
Soil	51.7	8.64E3
Sediment	47.8	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:

Table 2. STP Overall Chemical Mass Balance

	g/h	mol/h	percent
Influent	1.00E+001	8.8E-003	100.00
Primary sludge	2.50E-002	2.2E-005	0.25
Waste sludge	1.50E-001	1.3E-004	1.50
Primary volatilization	5.46E-023	4.8E-026	0.00
Settling volatilization	1.49E-022	1.3E-025	0.00
Aeration off gas	3.66E-022	3.2E-025	0.00
Primary biodegradation	1.76E-003	1.5E-006	0.02
Settling biodegradation	5.27E-004	4.6E-007	0.01
Aeration biodegradation	6.93E-003	6.1E-006	0.07
Final water effluent	9.82E+000	8.6E-003	98.15
Total removal	1.85E-001	1.6E-004	1.85
Total biodegradation	9.22E-003	8.1E-006	0.09

Reactive Red 239 displayed low biodegradability (< 20%) in a ready 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 pHs (extrapolated half-lifes at 25°C are 96 days at pH 4, 9.6 days at pH 7 and < 1 day at pH 9). 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 Red 239 has a measured log Kow of < -2. 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 pHs, 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 pHs, it can be concluded that it is unlikely that Reactive Red 239 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.

The results of a study OECD TG 309 study (pelagic test option) show a fast degradation of the test item in aerobic natural water. Transformation of Reactive Red 239 started directly after application. About 50 % transformation was reached within 3 days, after 22 days the detected concentration was < 10 % of the applied concentration. The test item was degraded to only one metabolite. This metabolite was formed by an elimination of the terminal alkyl sulfate moiety. This metabolite
was also formed in the abiotic controls at the end of the study in equal quantities. This result indicates that the degradation is driven by an abiotic process. The DTx values of Reactive Red 239 from this study are given in Table 3:

Table 3. Data of Kinetic Fit and DTx Values of Reactive Red 239

	DTx values in days [30µg/L]	DTx values in days [100µg/L]
DT50	3.13	3.03
DT90	10.4	10.1

The DT50 and DT90 test results underline a rapid abiotic degradation of the substance in the water compartment and can therefore not be classified as a persistent pollutant for the environment.

Finally, Reactive Red 239 demonstrates low acute toxicity in mammalian studies therefore in the event of exposure to environmental organisms, effects due to secondary poisoning can be excluded.