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Biodegradation in water

Biodegradability of [μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt (CAS no. 75173 -68 -1) is predicted using QSAR toolbox version 3.3 (2018) with logKow as the primary descriptor. Test substance undergoes 0.8% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical [μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt was estimated to be not readily biodegradable in water.

Additional information

Biodegradation in water

Predicted data for the target compound [μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt (CAS No. 75173-68-1) and various supporting weight of evidence studies for its structurally and functionally similar read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2018) using OECD QSAR toolbox version 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical[μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt(CAS No. 75173-68-1) was estimated.Test substance undergoes 0.8% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical[μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium saltwas estimated to be not readily biodegradable in water.

 

In a supporting weight of evidence study from experimental study report (Sustainability Support Services (Europe) AB, report no. 2519-30-4/01/2016/RBD, 2016) for the read across chemical Tetrasodium 1-acetamido-2-hydroxy-3-(4-((4-sulphonatophenylazo)-7-sulphonato-1-naphthylazo))naphthalene-4,6-disulphonate (CAS no. 2519-30-4),28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the read across item tetrasodium 1 -acetamido-2 -hydroxy-3 -(4 -((4 -sulphonato phenylazo)-7 -sulphonato-1 -naphthylazo))naphthalene-4,6 -disulphonate, CAS No. 2519 -30 -4. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 30 mg/L, while that of inoculum was 10 ml/l. 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 BOD28 value of tetrasodium 1 -acetamido-2 -hydroxy-3 -(4 -((4 -sulphonatophenylazo)-7 -sulphonato-1 -naphthylazo))naphthalene-4,6 -disulphonate, CAS No. 2519 -30-4 was observed to be 0.050mgO2sup>/mg. ThOD was calculated as 1.088 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 4.596%.Based on the results, the test item, under the test conditions, was considered to be not readily biodegradable at 20 ± 1°C over a period of 28 days.

 

For the read across chemical Disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate (CAS no. 4548-53-2), 28-days Manometric respirometry testfollowing the OECD guideline 301Fto determine the ready biodegradability of the test item disodium 3- [(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 -sulphonate, CAS No. 4548 -53 -2 (Sustainability Support Services (Europe) AB, report no. 4548-53-2/01/2016/RBD, 2016). The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 30 mg/L, while that of inoculum was 10 ml/l. 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 BOD28 value of disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate, CAS No. 4548-53-2 was observed to be 0.188 mgO2sup>/mg. ThOD was calculated as 1.464 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 12.807 %.Based on the results, the test item, under the test conditions, was considered to be not readily biodegradable at 20± 1°C over a period of 28 days.

 

On the basis of above results for target chemical [μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt (from OECD QSAR toolbox version 3.3, 2018) and for its read across substance (from UERL study report), it can be concluded that the test substance [μ-[[3,3'-[azoxybis[(2-hydroxy-p-phenylene)azo]]bis[4-hydroxynaphthalene-2,7-disulphonato]](8-)]]dicopper, tetrasodium salt can be expected to be not readily biodegradable in nature.