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Short term toxicity to aquatic invertebrates:

Based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on daphnia magna was predicted for 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6). Based on the intoxication of test organism the EC50 value was estimated to be 308.738 mg/l when 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid exposed to daphnia magna for 48 hrs. Based on this value it can be concluded that the substance 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acidis considered to be not toxic to aquatic environment and not classified as per the criteria mentioned in CLP regulation.

Toxicity to aquatic algae and cyanobacteria:

Based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was predicted for 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6). Based on the growth rate inhibition of algae, the EC50 value was estimated to be 135.52 mg/l when 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid exposed to Desmodesmus subspicatus for 72hrs. Based on this value it can be concluded that the substance 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid (6259-53-6) is considered to be not toxic to aquatic environment as per the criteria mentioned in CLP regulation.    

Additional information

Summarized result of toxicity of 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) on the growth and other activity of aquatic invertebrates, algae and cyanobacteria by considering the data for target as well as RA chemical which was selected on the basis of structural similarity and log Kow as the primary descriptor are as follows:  

Short term toxicity to aquatic invertebrates:

Various predicted data for the target compound 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) and supporting weight of evidence studies for its closest read across substance with structural similarity and log Kow as the primary descriptor were reviewed for the toxicity on the invertebrates end point which are summarized as below: 

In a prediction done by SSS (2017), based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on daphnia magna was predicted for 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6). Based on the intoxication of test organism the EC50 value was estimated to be 308.738 mg/l when 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid exposed to daphnia magna for 48 hrs. Based on this value it can be concluded that the substance 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acidis considered to be not toxic to aquatic environment and not classified as per the criteria mentioned in CLP regulation.     

 

 

Similarly in a supporting weight of evidence study from ABITEC report for (130-23-4) study were to determine the toxicity of a chemical 4-amino-5-hydroxynaphthalene-1,7- disulphonic acid on the growth of water flea daphnia magna. Determination of the inhibition of the mobility of daphnids was carried out with the substance 4-amino-5-hydroxy -naphthalene-1,7-disulphonic acid according to OECD Guideline 202. The test substance was tested at the concentrations of 0 for 3 controls and 5, 10, 25, 100, 200 mg/L for test chemical. Effects on immobilisation were observed for 48 hours. The median effective concentration (EC50) for the test substance, 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid, in Daphnia magna was determined to be 500 mg/L for immobilisation effects. This value indicates that the substance 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid is likely to be non-hazardous to aquatic invertebrates and cannot be classified as toxic as per the CLP criteria.

 

Similarly in a third supporting weight of evidence study from Chemosphere, 1994 for the structural similar read across chemical (121-57-3) toxicological profile for the sulfonic acids were study. Total 24hrs of exposure was provided to the daphnia magna. From the study the EC50 value for short term toxicity to aquatic invertebrates for Sulfanilic acid (121-57-3) in 24 hrs was determined to be 109.13 mg/l. Based on the result, Sulfanilic acid (121-57-3) was considered as not classified as per the CLP regulations.

 

Further study for the read across chemical (98-40-8) supports the classification of target chemical. Study for the read across chemical was taken from Chemosphere 1994. Study was conducted to determine the toxic nature of chemical 2-(Ethylamino) toluene-4-sulphonic acid on the mobility of daphnia magna. The EC50 value for short term toxicity to aquatic invertebrates daphnia magna for 2-(Ethylamino)toluene-4-sulphonic acid in 24 hrs and 48hrs was determined to be 170 mg/l and 154 mg/l. Based on the EC50 value, it can be concluded that the chemical 2-(Ethylamino) toluene-4-sulphonic acid was nontoxic and can be consider to be not classified as per the CLP classification criteria.

 

Similarly fifth study was conducted on the read across chemical selected on the basis of structure similarity 2-Naphthalenecarboxylic acid, 3-hydroxy-4-[(4-methyl-2-sulfophenyl) azo]-, calcium salt (D & C Red no. 7) (5281-04-9) from the OECD SIDS Initial Assessment Report. Detection of the effect of D & C Red no. 7 on the growth of daphnia magna by following standard OECD guideline. The test was performed in static system by following the OECD guideline. Daphnia magna exposed with the chemical for 24hrs. Based on the immobilization of daphnia magna by the chemical 2-Naphthalenecarboxylic acid, 3-hydroxy-4-[(4-methyl-2-sulfophenyl) azo]-, calcium salt (D & C Red no. 7) for 24hrs, the EC50 was 280 mg/l.

On the basis of above results for target 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) (from OECD QSAR toolbox version 3.4) and for its read across substance from ABITEC report, peer reviewed journal Chemosphere 1994 and SIDS report, it can be concluded that the test substance 4-hydroxy-6-(methylamino) naphthalene -2-sulfonic acid (6259-53-6) is not toxic and can be consider to be not classified as toxic as per the CLP classification criteria. 

 

Toxicity to aquatic algae and cyanobacteria:

Various predicted data for the target compound 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) and supporting weight of evidence studies for its closest read across substance with structural similarity and log Kow as the primary descriptor were reviewed for the toxicity on the aquatic algae and cyanobacteria end point which are summarized as below: 

In a prediction done by SSS (2017), based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, toxicity on Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was predicted for 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6). Based on the growth rate inhibition of algae, the EC50 value was estimated to be 135.52 mg/l when 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid exposed to Desmodesmus subspicatus for 72hrs. Based on this value it can be concluded that the substance 4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid (6259-53-6) is considered to be not toxic to aquatic environment as per the criteria mentioned in CLP regulation.     

 

Similarly in the second predicted study from Danish QSAR database, for the toxicity to algae was used based on the prediction done using the three different models i.e, Battery, Leadscope and SciQSAR used within Danish QSAR database, the short term toxicity on green algae was predicted for test substance  4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid (CAS: 6291 -53 -6). The average EC50 value was given by the third model i.e, Battery model. On the basis of effects observed in a static freshwater system, the effect concentration EC50 value for the substance  4-hydroxy-6-(methylamino) naphthalene-2-sulfonic acid is estimated to be 2698.016 mg/l for Pseudokirchneriella subcapitata during 72 hr exposure duration. Thus, on the basis of EC50 value, it can be concluded that the test chemical  4-hydroxy- 6-(methylamino) naphthalene -2-sulfonic acid can be considered as non-toxic to green algae at environmentally relevant concentrations and can be considered not-classified as per the CLP classification criteria.

 

Further weight of evidence studies for the read across chemicals supports the above predicted study for the target chemical. By considering data for supporting weight of evidence study from ABITEC report 2016 for read across chemical 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid (130-23-4) toxicity experiment was conducted for evaluating the effect of read across substance. Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 4-amino-5-hydroxynaphthalene- 1,7-disulphonic acid according to OECD Guideline 201. The test substance was dissolved in OECD growth medium and tested at the concentrations 0, 2.2, 11, 25, 55 and 120 mg/L. Effects on the growth rate of the organism were studied. The median effective concentration (ErC50) for the test substance, 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid, in Desmodesmus subspicatus was determined to be 129.4 mg/L. Based on this ErC50 value and after comparing with CLP criteria for aquatic classification of the substance it is concluded that the substance 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid does not exhibit toxicity to aquatic algae (Desmodesmus subspicatus) and not classified as toxic as per the CLP classification criteria.

 

Similarly for the same read across chemical, toxicity study was conducted on algae and reported from UERL lab, 2016, The effect of test item 4-amino-5-hydroxynaphthalene-1,7 -disulphonic acid, CAS No. 130-23-4 was studied on the growth of fresh water green alga Chlorella vulgaris. The study was conducted following OECD guideline 201- Alga, growth inhibition test. The test concentration chosen for the study were 6.25mg/l, 12.5mg/l, 25mg/l, 50mg/l, 100mg/l and 200mg/l. The test concentrations were prepared using stock solution of the test item using mineral media. The green alga was exposed to the test concentration for a period of 72 hours to observe average specific growth rate and % growth inhibition under the effect of the test item. EC50 calculated graphically through probit analysis was observed to be >200mg/l. Thus, based on the EC50 value, test substance 4-amino-5-hydroxynaphthalene-1,7-disulphonic acid can be classified as not hazardous and nontoxic as per the criteria of CLP regulation.

 

Study in the study for the read across chemical (98-37-3) from Water Research Pergamon Press 1968, Short term toxicity to Chlorella pyrenoidosa (green algae) study was carried out for 72 hrs. Emerson strain of bacteria free, experimentally reproducible cultures of Chlorella pyrenoidosa was used as a test organism. The procedure involve the use of test tubes in both the screening and final tests. These test tubes contained 15 ml of inorganic culture medium, a predetermined amount of test chemical and 5 ml of algal culture. The tubes were incubated for 72 hrs andchlorophyll content of the algal suspensions was measured every 24 hrs. For chlorophyll measurement, the chlorophyll pigment was extracted with hot methanol in two separate extractions. An algal suspension, 2.5 ml, was removed from the test tube, centrifuged, washed with distilled water, and recentrifuged in preparation of chlorophyll analysis. After discarding the supernatant, the deposited cell material was coagulated by placing the cells in a boiling water bath for about 40 sec. About 2.5 ml of methanol were used in each extraction. Finally, the chlorophyll solution was diluted to a total volume of 10 ml with an acetone-water mixture (80 per cent by volume). A Beckman Spectrophotometer, Model DB, was used to measure the chlorophyll content according to MACKIN~v (1941) and ARNON (1949). For this a wavelength of 652 m/z was used because different proportions of chlorophyll a and b least affect the results at this wavelength. Control tubes containing no test chemical was also used in the experiment. Knop's solution, including the Hutner-EDTA microelement addition, was used as the culture medium.pH of culture medium was adjusted to 7.0 using KOH before use. The test organism was maintained under steady-state conditions, provided a chlorophyll content of 38 mg/l. Environmental control was rigidly maintained. The temp. of water bath was 25 ± 1°C. The test apparatus consisted of a constant-temperature water bath, a light source containing four 200W fluorescent lamps with attached aluminum reflectors, a gas manifold to supply an air-CO2 mixture to each test tube, and a rack to hold the test tubes. A stream of 5 % CO2 in air gas mixture was supplied to culture medium in order to provide the inorganic carbon source and also to keep the algal ceils in suspension. Based on destruction of chlorophyll of test organism by test chemical Amino-1-phenol-4-sulfonic acid, the LOEC value was determine to be1500 mg/l and as no toxic effect at 1000 mg/l was observed, the NOEC value was determine to be 1000 mg/l. Thus, based on this value, it can be concluded that the substance can be considered as non-toxic to aquatic organisms and thus cannot be classified as hazardous as per the CLP criteria.

 

Similarly for the another read across chemical D & C Red no. 7 (5281-04-9) from HPVIS and SIDS report, Detection of the effect of D & C Red no. 7 on the growth of Selenastrum capricornutum ATCC 22662 was done by following standard 202 OECD guideline. The test was performed in static system by following the OECD guideline. Selenastrum capricornutum ATCC 22662 exposed with the chemical for 72hrs. Based on the biomass inhibition of Selenastrum capricornutum ATCC 22662 by the chemical 2-Naphthalenecarboxylic acid, 3-hydroxy-4-[(4-methyl-2-sulfophenyl)azo]-, calcium salt (D & C Red no. 7) for 72hrs, the NOEC was 5.8 mg/l, and the EC50 was 190 mg/l. Based on the EC50 value it was concluded that the chemical D & C Red no 7 was nontoxic and can be consider to be not classified as toxic as per the CLP classification criteria.

On the basis of above results for target 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) (from OECD QSAR toolbox version 3.4 and Danish QSAR) and for its read across substance from ABITEC report, UERL report, peer reviewed journal Water Research Pergamon Press 1968 and HPVIS, SIDS report, it can be concluded that the test substance 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) was not toxic to algae and can be consider to be not classified as toxic as per the CLP classification criteria. 

 

Thus according to the studies on both aquatic organisms invertebrates and algae, it can be concluded that the 4-hydroxy-6-(methylamino)naphthalene-2-sulfonic acid (6259-53-6) can be considered as non-toxic to aquatic organisms and thus cannot be classified as hazardous as per the CLP classification criteria.