Disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate

Endpoint summary

Additional information

Stability:-

Phototransformation in air:

The atmospheric oxidation half-life of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate was estimated using the level III multimedia model. It was estimated that the substance is persistent in air medium as the half life period of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate in air is 4 days. This indicates that disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate is not likely to photo transformed in air. 

OVERALL OH Rate Constant =0.000000000004cm3/molecule-sec.

Hydrolysis:

The Hydrolysis rate constant of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate is estimated to be 0.0000000000040204 (4.0204 E-12) cm3/molecule-sec. at half life of the 31.925 Hrs.The estimated half life of the substance indicates that the substance is slowly hydrolysable.

Phototransformation in water :

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Phototransformation in Soil :

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Biodegradation:

Biodegradation in water: screening tests:

The half life period of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate in water is 38 days and based on this value it can be concluded that the chemical is not persistent in water medium since the half life is less than the threshold of 60 days (to qualify the chemical as persistent). Also the diffusion percentage of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate in water medium is 9 %. This coupled with the dilution of water shall result in ready biodegradability of the chemical.

Medium	Half life in Days	Percent in medium
Water	38	9%

Biodegradation in water and sediment: simulation tests:

Based on the Level III Fugacity Model, the half life period of the disodium 6-hydroxy-5-[(4-sulphonatophenyl) azo] naphthalene-2-sulphonate was estimated. The half period of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate in water is 38 days (912 hrs) therefore it is considered that the substance will qualify as not persistent as the half life does not exceed the EPA criteria of 60 days. So, it can be confirmed that the substance is readily biodegradable in water medium where as in sediment the half life is 340 days (8160 hrs). 

Based on this value, it can be inferred that the substance is persistent in sediment medium and is not readily biodegradable probably due to the anaerobic conditions existing in most sediments. However, it can be observed that disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate less diffuse in the sediment medium since it's percentage in the sediment medium is reported to be 13% and hence persistence in the sediment compartment is not likely to be critical.

PBT profiler estimation:

  

Medium	Half life in Days	Percent in medium
Water	38	9%
Sediment	340	13%

   

Biodegradation in soil:

The PBT Profiler & EPI Suite has estimated that disodium 6-hydroxy-5-[(4-sulphonatophenyl) azo]naphthalene-2-sulphonate is expected to be found predominantly in soil and its persistence estimate is based on its transformation in this medium. Its half-life in soil, 75 days (1800 hrs). Does not exceed the threshold of 120 days as per Annex XIII of REACH. Thereforedisodium 6-hydroxy-5-[(4-sulphonatophenyl) azo]naphthalene-2-sulphonateis estimated to be not persistent in the soil environment.

PBT Profiler Estimate:

Media	Half-Life (days)	Percent in Medium
Soil	75	78%

Fugacity Model by EPI Suite estimation database:

	Mass Amount (percent)	Half-Life (days)	Emissions (kg/hr)
Soil	77.9	1.8e+003	1000

Bioaccumulation:

Bioaccumulation is the process by which the chemical concentration in an aquatic organism achieves a level that exceeds that in the water, as a result of chemical uptake through all possible routes of exposure. The relationship between bioaccumulation and bio-concentration is that, chemicals that have the potential to bioconcentrate also have the potential to bioaccumulate. Bioaccumulation is closely related to the Bioconcentration factor (BCF).

The estimated BCF of the key study was obtained to be 3.2.Supporting study also indicate the BCF value to be 3.1 and 3.09.This low value of BCF of disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate indicates its non bioaccumulative nature as the BCF factor is less than the bio-concentration threshold of 2000. 

Adsorption / desorption:

According to EPI (Estimation Programs Interface) Suite soil adsorption coefficient (Koc) value for disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate was estimated to be 25110 at 25°C by MCI method. This value indicates that disodium 6-hydroxy-5-[(4-sulphonatophenyl)azo]naphthalene-2-sulphonate is non mobile in soil. This value is equivalent to 20088 at 20°C.