1-phenylazo-2-naphthol

Endpoint summary

Description of key information

Stability

Hydrolysis

The hydrolysis study of 1-phenylazo-2-naphthol was predicted using OECD QSAR toolbox version 3.3 (2017) to predict the hydrolysis half-life of test compound 1-phenylazo-2-naphthol (CAS No.842-07 -9). The half-life of 1-phenylazo-2-naphthol was estimated to be 108.89 days at temperature 25degC, indicating that the substance 1-phenylazo-2-naphthol is not hydrolysable.

Biodegradation

Biodegradation in water

The carbon dioxide evolution test (former Sturm test) is a static method to evaluate the ultimate aerobic biodegradability of a test substance in water . Activated sludge was obtained from laboratory wastewater plant treating municipal sewage. Activated sludge of a concentration of 30 mg/I dry substance was pre-aerated for about two days before the start of the test.Mixtures of the test substance, a defined inorganic medium and a non pre-adapted inoculurn (e .g. activated sludge or effluent of a municipal or laboratory waste water treatment plant) are incubated and aerated at room temperature up to 28 days. The biologically produced carbon dioxide is trapped in a 0,25 mol. potassium hydroxide solution. The production of carbon dioxide (C02) is a clear indication of biodegradation . The measured amount of carbon dioxide at the end of the test is compared with the calculated maximal theoretical production (ThC02) and indicated as biodegradation degree in percent. The conductivity shift of the absorption solution is used for calculating of the C02 production. Biodegradation degree of the reference substance after 14 days (% CO2/ThCO2): 60 - 70%. The percentage degradation of the test substance was determined to be <10% in 28 days by CO2/ThCO2 parameter. Thus, the test substance1-phenylazo-2-naphthol (Sudan Orange 220)is considered to be not readily biodegradable according to OECD criteria.

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 1-phenylazo- 2-naphthol (C.I. Solvent Yellow 14) (CAS No. 842 -07 -9). If released in to the environment,7.59% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of C.I. Solvent Yellow 14 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 C.I. Solvent Yellow 14 in sediment is estimated to be 337.5 days (8100 hrs). Based on this half-life value (337.5 days), it indicates that the chemical 1-phenylazo-2- naphthol (C.I. Solvent Yellow 14) is persistent in sediment.

Biodegradation in soil

The half-life period of1-phenylazo-2-naphthol (C.I. Solvent Yellow 14) (CAS No. 842 -07 -9) 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, 70.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of C.I. Solvent Yellow 14 in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of1-phenylazo-2-naphthol (C.I. Solvent Yellow 14), 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.

Bioaccumulation

Bioaccumulation: aquatic / sediment

Based on the predicted data by BCFBAF Program (v3.01) model,PBT profiler and INERIS database the Bioaccumulation factor (BCF) was predicted to be 10 L/kg wet-wt at 25 deg.C. Based on the BCF concentration it is concluded that the test chemical 1-phenylazo-2-naphthol is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

Transport and distribution

Adsorption / desorption

The Soil Adsorption Coefficient i.e Koc value of 1-phenylazo-2-naphthol  was estimated using EPI suite  KOCWIN Program (v2.00) program and the value was reported as Koc 53250 L/kg (log Koc=4.726)  by means of MCI method at 25 deg.C. This Koc value indicates that the substance 1-phenylazo-2-naphthol has a very strong sorption to soil and  sediment and show negligible migration potential to groundwater.

Additional information

Stability

Hydrolysis

In a different studies, 1-phenylazo-2-naphthol (CAS No. 842 -07 -9) has been investigated for its hydrolysis potential to a greater or lesser extent. These include predicted and experimental study for target substance 1-phenylazo-2-naphthol (CAS No. 842 -07 -9) and for its closest read across substance 1-[(2,5-dimethoxyphenyl)diazenyl]-2-naphthol (Citrus Red 2) (CAS No.- 6358-53-8) by considering its structure-activity relationships, were reviewed and are summarized as follows:

 

The hydrolysis study of 1-phenylazo-2-naphthol was predicted by SSS (2017) using OECD QSAR toolbox version 3.3 (2017) to predict the hydrolysis half-life of test compound 1-phenylazo-2-naphthol (CAS No.842-07 -9). The half-life of 1-phenylazo-2-naphthol was estimated to be 108.89 days at temperature 25degC, indicating that the substance 1-phenylazo-2-naphthol is not hydrolysable.

 

This is supported by the study from an authoritative database (Hazardous Substances Data Bank (HSDB);2017) for a read across substance 1-[(2,5- dimethoxy phenyl)diazenyl]-2-naphthol (Citrus Red 2) (CAS No.- 6358-53-8).The substance 1-[(2,5-dimethoxyphenyl)diazenyl]-2-naphthol (Citrus Red 2) (CAS No.- 6358- 53-8) is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions.

  

Based on the above available studies for the target and read across substance, it can be concluded that the test substance 1-phenylazo-2-naphthol (CAS No. 842 -07 -9) is not expected to undergo hydrolysis in the environment i.e., it is not hydrolysable.

Biodegradation

Biodegradation in water

Experimental study and publication data for the test compound 1-phenylazo-2-naphthol (C.I. Solvent Yellow 14) (CAS No. 842-07-9) were reviewed for the biodegradation end point which are summarized as below:

 

The carbon dioxide evolution test (former Sturm test) is a static method to evaluate the ultimate aerobic biodegradability of a test substance Sudan Orange 220 (CAS no. 842-07-9) in water (Sustainability Support Services (Europe) AB has letter of access, Experimental report no. 03/0063/36/1, 2003). Activated sludge was obtained from laboratory wastewater plant treating municipal sewage. Activated sludge of a concentration of 30 mg/I dry substance was pre-aerated for about two days before the start of the test. Mixtures of the test substance, a defined inorganic medium and a non pre-adapted inoculurn (e .g. activated sludge or effluent of a municipal or laboratory waste water treatment plant) are incubated and aerated at room temperature up to 28 days. The biologically produced carbon dioxide is trapped in a 0,25 mol. potassium hydroxide solution. The production of carbon dioxide (C02) is a clear indication of biodegradation. The measured amount of carbon dioxide at the end of the test is compared with the calculated maximal theoretical production (ThC02) and indicated as biodegradation degree in percent. The conductivity shift of the absorption solution is used for calculating of the C02 production. Biodegradation degree of the reference substance after 14 days (% CO2/ThCO2): 60 - 70%. The percentage degradation of the test substance was determined to be <10% in 28 days by CO2/ThCO2 parameter. Thus, the test substance 1-phenylazo-2-naphthol (Sudan Orange 220) is considered to be not readily biodegradable according to OECD criteria.

 

Biodegradation study of Sudan I was performed (Haiyan Xu et. a; 2010) (CAS no. 842-07-9). The test is carried at a temperature of 37ᵒC with a duration period of 2 days. The anaerobic bacterial species used in the study were obtained from the American Type Culture Collection (ATCC). All strains were preserved at -80ᵒC in 10 to 15% glycerol stocks and revived as needed. The bacterial strains were grown anaerobically at 37ᵒC by using BHI broth or MRS supplemented with various Sudan dye. A loopful for each strain was cultured in static conditions at 37ᵒC for 24 h in an Erlenmeyer flask containing 10 ml medium for use as a seed culture. The bacterial seed cultures of 1.5 ml were inoculated into flasks containing 100 ml BHI broth. Dye stock solutions were added to the medium at final concentrations of 10µg/ml, the cultures were incubated at 37ᵒC in an anaerobic chamber for 2 days without agitation. Metabolites of the reduction of the test compound Sudan I were isolated and identified by HPLC andLiquid chromatography/ electrospray ionization mass spectrometric (LC/ESI-MS).Reduction of the dyes was determined by measuring the disappearance of the absorbance at 500 nm immediately after extraction with ethyl acetate as well. The results are presented in percentage (%) obtained by the means from triplicate incubations. Among the tested bacterial strains, B.ovatus, B. uniformis, B. distasonis, B. fragilis, B. thetaiotaomicron, B. caccae, B. infantis, C. perfringens, C. butyricum, C. difficle, C. indolis, C. clostridioforme, E. aerofaciens, E. faecalis, E. faecium, F. russi, F. nucleatum, L. paracasei, L. rhamnosus, R. obeum and R. gnavus were able to completely degrade (100%) the test substance Sudan I.

The bacteria which are unable to degrade the Sudan I are Bifidobacterium longum, B. Adolescentis, B. catenulatum, B. angulatum, Clostridium ramosum, Clostridium leptum, Eubacterium tenue, Escherichia coli, Lactobacillus bifidus, Lactobacillus reuteri, Lactobacillus ruminis, and Peptostreptococcus magnus, respectively. The metabolite produced from Sudan I by E. faecalis was identified as aniline, based on an identical retention time of 4.05 min and ions atm/z94 [MH+] and 135 [MH++acetonitrile].1 -amino-2 -naphthol from Sudan I dye could not be detected in the extracted samples. No metabolites of Sudan I dye produced by E. coli was detected by LC/ESI-MS, indicating that the dyes were not degraded by the bacterium. Thus, based on percentage degradation of test substance, 1-phenylazo-2-naphthol (Sudan I) is considered to be readily biodegradable in nature.

 

Although publication study result indicates that the chemical is readily biodegradable in anaerobic conditions, but based on the experimental result for aerobic biodegradation (key study), it is concluded that the test substance 1-phenylazo-2-naphthol (C.I. Solvent Yellow 14) is considered 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 1-phenylazo- 2-naphthol (C.I. Solvent Yellow 14) (CAS No. 842 -07 -9). If released in to the environment,7.59% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of C.I. Solvent Yellow 14 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 C.I. Solvent Yellow 14 in sediment is estimated to be 337.5 days (8100 hrs). Based on this half-life value (337.5 days), it indicates that the chemical 1-phenylazo- 2-naphthol (C.I. Solvent Yellow 14) is persistent in sediment.

 

Biodegradation in soil

The half-life period of1-phenylazo-2-naphthol (C.I. Solvent Yellow 14) (CAS No. 842 -07 -9) 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, 70.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of C.I. Solvent Yellow 14 in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of1-phenylazo-2-naphthol (C.I. Solvent Yellow 14), 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.

Bioaccumulation

Bioaccumulation: aquatic / sediment

Experimental and estimated data of Bioaccumulation property for the target chemical 1-phenylazo-2-naphthol (CAS No. 842-07-9) and its read across chemical were reviewed to summarize as follows:  

 

From predicted model EPI suite 2017 using BCFBAF Program (v3.01) model,PBT profiler and INERIS database the Bioaccumulation factor (BCF) was predicted to be 10 L/kg wet-wt at 25 deg.C.Based on the BCF concentration it is concluded that the test chemical 1-(phenyldiazenyl)-2-naphthol is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000. 

 

From HSDB database; 2017 the read across chemical Sodium 4-[(4-hydroxy-1-naphthyl)azo] benzene sulphonate i.e C.I. ACID ORANGE 20 (CAS No. 523-44-4) indicate an estimated BCF value of 0.5 was calculated for C.I. Acid Orange 20, using an estimated log Kow of -0.14 and a recommended regression-derived equation. According to a classification scheme, this BCF value suggests that bioconcentration in aquatic organisms is low.

 

Data for another read across Orange G (CAS No. 1936-15-8) from same database i.e HSDB indicate that the estimated BCF value of 0 was calculated for Orange G, using an estimated log Kow of -4.56 and a recommended regression-derived equation. This BCF value suggests that bioconcentration of Orange G in aquatic organisms will not be an important fate process.

 

Similarly information for another read across C.I. Food Yellow 3 (CAS No. 2783-94-0) indicates the ionic character of C.I. Food Yellow 3 suggests the potential for bioconcentration in aquatic organisms is expected to be low.

 

Thus, based on the above all studies it is concluded that the test substance 1-phenylazo-2-naphthol (CAS No. 842-07-9) is non bioaccumulative in aquatic environment.

 

Transport and distribution

Adsorption / desorption

Predicted and experimental data of adsorption endpoint for the target chemical 1-phenylazo-2-naphthol (CAS No. 842-07-9) and its read across chemical were reviewed to summarize as follows:  

 

The Soil Adsorption Coefficient i.e Koc value of 1-phenylazo-2-naphthol  was estimated using EPI suite  KOCWIN Program (v2.00) program and the value was reported as Koc 53250 L/kg (log Koc=4.726)  by means of MCI method at 25 deg.C. This Koc value indicates that the substance 1-phenylazo-2-naphthol has a very strong sorption to soil and sediment and show negligible migration potential to groundwater.

 

Whereas Chemspider - ACD/PhysChem Suite prediction model indicates that the soil adsorption coefficient i.e Koc value of test substance 1-phenylazo-2-naphthol was estimated to be 6358.49  i.e Log Koc= 3.8033 at pH 5.5 and 6358.48  i.e Log Koc=3.8034 at pH 7.4.This Koc value indicates that the substance 1-phenylazo-2-naphthol has a strong sorption to soil and sediment and show negligible to slow migration potential to groundwater.

 

Information for the read across chemical Oil pink (CAS No. 1229-55-6) From HSDB authorative database (2017) indicates the adsorption coefficient (Koc) of substance Oil pink i.e 1-[(2-methoxyphenyl)azo]-2-naphthol as 290000 using a measured log Kow of 7.5 and regression derived equation. This Koc value indicates that oil pink will be immobile in soil.

 

Information for another read across substance 1 -[(2,5 -dimethoxyphenyl)diazenyl]-2-naphthol (CAS No. 6358 -53 -8) from same data source i.e HSDB indicate that using a structure estimation method based on molecular connectivity indices, the Koc of 1 -[(2,5 -dimethoxyphenyl)diazenyl]-2-naphthol can be estimated to be 23000. This Koc value indicates that the substance 1 -[(2,5 -dimethoxyphenyl)diazenyl]-2 -naphthol has strong sorption to soil and sediment and show negligible to slow migration potential to ground water.

Thus based on the above all studies it is concluded that the test substance 1-phenylazo-2-naphthol (CAS No. 842-07-9) has very strong sorption to soil and sediment.