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

Endpoint summary

Additional information

Biodegradation:

Biodegradation in water: screening tests:

28-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test item Disodium 6 -hydroxy-5 -[(4 -sulphonatophenyl)azo]naphthalene-2 -sulphonate (CAS No.2783 -94 -0)(Experimental study report, 2018). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used for this study. 1 polyseed capsule were added in 500 ml D.I water and then stirred for 1 hour for proper mixing and functioning of inoculum. This gave the bacterial count as 107 to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l. OECD mineral medium was used for the study. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 75.3%. Degradation of Sodium Benzoate exceeds 46.38 % on 7 days & 61.44 % on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.1 mgO2/mg. ThOD was calculated as 1.2 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 91.66%. Based on the results, the test item, under the test conditions,was considered to bereadily biodegradable in nature.

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