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Biodegradation in water

Biodegradability of 2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt (CAS no. 93941 -74 -3) is predicted using QSAR toolbox version 3.3 (2018) with logKow as the primary descriptor. Test substance undergoes 6.7% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt was estimated to be not readily biodegradable in water.

Additional information

Biodegradation in water

Predicted data for the target compound 2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt (CAS No. 93941-47-3) and various supporting weight of evidence studies for its structurally and functionally 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 chemical2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt(CAS No. 93941-47-3) was estimated.Test substance undergoes 6.7% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium saltwas estimated to be not readily biodegradable in water.

 

In a supporting weight of evidence study from study report (Sustainability Support Services (Europe) AB, Report no. 4548-53-2/01/2016/RBD, 2016) 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 301F to determine the ready biodegradability of the read across item disodium 3- [(2,4 -dimethyl-5 -sulphonatophenyl)azo]-4 -hydroxynaphthalene-1 -sulphonate. 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 mgO2sup>/mg. ThOD was calculated as mgO2/mg. Accordingly, the % degradation of the read across item Disodium 3-[(2,4-dimethyl-5-sulphonatophenyl)azo]-4-hydroxynaphthalene-1-sulphonate 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.

 

For the read across chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt (CAS no. 2611-82-7) from peer reviewed journal (U. Pagga and O. Brown, 1986), biodegradation study was carried out for 48 days for evaluating the percentage biodegradation of the read across chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt using modified OECD Guideline 302B. Activated sludge was used as a test inoculum. The sources of the activated sludge were treatment plants conveniently located to the laboratories carrying out the test. These treatment plants received communal and/or industrial wastewater. Concentration of inoculum i.e, activated sludge used was 0.5 g/l and initial test substance conc. used in the study was 100 mg/l. Analytical methods involve the measurement of extinction at absorption maximum 412 nm and DOC (dissolved organic carbon).The percentage degradation of substance 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 5% by DOC removal. Based on the limit values for classification of Static Test – the test chemical was classified in CATEGORY ‘D’. Thus, the substance 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt is considered to be not readily biodegradable in nature.

 

Another biodegradation study was conducted for evaluating the percentage biodegradability of read across substance 1,3 -Naphthalenedisulfonic acid, 7 -hydroxy-8 -((4 -sulfo-1 -naphthalenyl)azo)-, trisodium salt (CAS no. 2611 -82 -7) (Toshihide Saito et. al, 1984). Activated sludge was used as a test inoculum obtained from municipal sewage. Test substance of conc. 500 mg/l was prepared and diluted as needed. The COD measurement was performed by the potassium dichromate reflux method based on Japanese Industrial Standards. In the BOD measurement, a sample solution was taken into a container. Then JIS-BOD testing solutions, i.e. 3 ml of A solution and 1 ml of B, C, D solutions were added to the sample solution, respectively. Then 5 ml of the supernatant of the municipal sewage activated sludge was added to the sample solution and diluted to 300 ml with water. Immediately, the BOD-time curve was recorded at 20~ using an Ohkura OM-200I type coulometer. The TOC measurement was carried out by a Yanagimoto TOC-ILW.BOD5, COD, ThOD and TOC value of the test chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 0.021, 0.65, 1.23 and 0.20 g/g, respectively. The BOD5/TOC ratio of chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt was determined to be 0.11 (i.e. ranges in between 0.08-0.89), indicating that the chemical is highly resistant to aerobic biodegradation. Thus, based on this value BOD5/TOC value, it can be concluded that the chemical 1,3-Naphthalenedisulfonic acid, 7-hydroxy-8-((4-sulfo-1-naphthalenyl)azo)-, trisodium salt is not readily biodegradable in nature.

 

In a supporting weight of evidence study from authoritative database (HSDB, 2017) for read across substancedisodium (5E)-6-oxo-5-[(4-sulfonatophenyl)hydrazinylidene]naphthalene-2-sulfonate (CAS no. 2783-94-0), biodegradation experiment was conducted for 5 days for evaluating the percentage biodegradability of read across substance disodium (5E)-6 -oxo-5 -[(4 -sulfonatophenyl)hydrazinylidene]naphthalene-2 -sulfonate under aerobic conditions. Sewage was used as a test inoculum for the study. The percentage degradation of substance disodium (5E)-6-oxo-5-[(4-sulfonatophenyl)hydrazinylidene]naphthalene-2-sulfonate was determined to be 0% by using BOD parameter in 5 days. Thus, based on percentage degradation, disodium (5E)-6-oxo-5-[(4-sulfonatophenyl)hydrazinylidene]naphthalene-2-sulfonate is considered to be not readily biodegradable in water.

 

On the basis of above results for target chemical 2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt(from OECD QSAR toolbox version 3.3, 2017) and for its read across substance (from UERL study report, peer reviewed journals and authoritative database HSDB), it can be concluded that the test substance 2-[[4-[[4-[[6-anilino-1-hydroxy-3-sulpho-2-naphthyl]azo]-1-naphthyl]azo]-6-sulpho-1-naphthyl]azo]benzene-1,4-disulphonic acid, magnesium sodium salt can be expected to be not readily biodegradable in nature.