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Biodegradation in water

Biodegradability of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS no. 6259 -53 -6) is predicted using QSAR toolbox version 3.4 (2017) with logKow as the primary descriptor. Test substance undergoes 1.48% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 4 -hydroxy-6 -(methylamino)naphthalene-2 -sulfonic acid was estimated to be not readily biodegradable in water.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound  4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS No. 6259 -53 -6). If released in to the environment, 13.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 4 -hydroxy-6 -(methylamino)naphthalene-2 -sulfonic acid in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.205%), indicates that 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid is not persistent in sediment.

 

Biodegradation in soil

The half-life period of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS No. 6259 -53 -6) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 86% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 4 -hydroxy-6 -(methylamino) naphthalene-2 -sulfonic acid in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Additional information

Biodegradation in water

Various predicted data for the target compound 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS No. 6259-53-6) and supporting weight of evidence studies for its structurally similar read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done by SSS (2017) using OECD QSAR toolbox version 3.4 with logKow as the primary descriptor, percentage biodegradability of test chemical4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid(CAS No. 6259-53-6) was estimated.Test substance undergoes 1.48% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acidwas estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid(CAS No. 6259-53-6) in the presence of mixed populations of environmental microorganisms was estimated.The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acidis expected to be not readily biodegradable.

 

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 (J-CHECK, 2017) and secondary source (HPVIS and OECD SIDS) for the read across chemical calcium 3-hydroxy-4-[(4-methyl-2-sulfonatophenyl)diazenyl]-2-naphthoate (CAS no. 5281-04-9), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance calcium 3 -hydroxy-4 -[(4 -methyl-2 -sulfonatophenyl)diazenyl]-2 -naphthoate (CAS no. 5281 -04 -9). The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. Activated sludge (non-adapted) was used as a test inoculums for the study. Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. The percentage degradation of substance calcium 3 -hydroxy-4 -[(4 -methyl-2 -sulfonatophenyl)diazenyl]-2 -naphthoate was determined to be 10 and 0% by BOD and HPLC parameter in 28 days. Thus, based on percentage degradation, calcium 3-hydroxy-4-[(4-methyl-2-sulfonato phenyl)diazenyl]-2-naphthoate is considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (from OECD QSAR toolbox version 3.4 and EPI suite, 2017) and for its read across substance (from peer reviewed journals, authoritative database J-CHECK and secondary source HPVIS & OECD SIDS), it can be concluded that the test substance 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid can be expected to be not readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound  4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS No. 6259 -53 -6). If released in to the environment, 13.8% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 4 -hydroxy-6 -(methylamino)naphthalene-2 -sulfonic acid in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.205%), indicates that 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid is not persistent in sediment.

 

Biodegradation in soil

The half-life period of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (CAS No. 6259 -53 -6) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (EPI suite, 2017). If released into the environment, 86% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 4 -hydroxy-6 -(methylamino) naphthalene-2 -sulfonic acid in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid, it is concluded that the chemical is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test substance 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid can be considered to be not readily biodegradable in nature.