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Environmental fate & pathways

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Biodegradation in water

Biodegradability of 2-methyl-4-nitroaniline (CAS no. 99 -52 -5) is predicted using QSAR toolbox version 3.3 with logKow as the primary descriptor (2017). Test substance undergoes 0.24% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 2-methyl-4-nitroaniline 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  2-methyl-4-nitroaniline (CAS No. 99 -52 -5). If released in to the environment, 16.2% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 2-methyl-4-nitroaniline in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the 2-methyl-4-nitroaniline is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 2-methyl-4-nitroaniline 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 0.173%), indicates that 2-methyl-4-nitroaniline is not persistent in sediment.

Biodegradation in soil

The half-life period of test chemical 2-methyl-4-nitroaniline (CAS No. 99 -52 -5) 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, 83.5% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2-methyl-4-nitroaniline in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 2-methyl-4-nitroaniline, 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: aquatic / sediment

From BCFBAF (v3.00) model of EPI suite and PBT profiler the estimated bio concentration factor (BCF) for 2-methyl-4-nitroaniline is 10 L/kg wet-wt which does not exceed the bioconcentration threshold of 2000.Thus it is concluded that 2-methyl-4-nitroaniline is not expected to bio accumulate in the aquatic environment.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge 4-nitro-o-toluidine(CAS No.99-52-5) was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The reference substances were chosen according to functional group similarity with the test substance and calibration graph prepared. The reference substances were 4 -methylaniline, aniline, nitrobenzene, xylene, ethylbenzene and toluene, having Koc value ranging from 1.9 to 2.649. The Log Koc value was found to be 2.0875 ± 0.0002 at 25°C.

Additional information

Biodegradation in water

Various predicted data for the target compound 2-methyl-4-nitroaniline(CAS No. 99-52-5) and weight of evidence studies for its 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 3.3 with logKow as the primary descriptor, percentage biodegradability of test chemical 2-methyl-4-nitroaniline(CAS No. 99-52-5) was estimated (2017).Test substance undergoes 0.24% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical 2-methyl-4-nitroaniline was 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 compound 2-methyl-4-nitroaniline (CAS No. 99-52-5) 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 2-methyl-4-nitroaniline is expected to be not readily biodegradable.

 

In a supporting weight of evidence study from authoritative database (J-CHECK. 2016), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of read across substance1,5 -naphthalinediamine (CAS no. 2243 -62 -1). 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 read across substance was determined to be 0 and 3% degradation by BOD and HPLC parameter in 28 days. Thus, based on percentage degradation, 1,5 -naphthalinediamine is considered to be not readily biodegradable in nature.

 

For another read across chemical naphthalene-1,8 -diamine (CAS no. 479 -27 -6), biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test substance naphthalene-1,8 -diamine (J-CHECK, 2016). 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 read across substance was determined to be 0, 9 and 1% by BOD, TOC removal and HPLC parameter in 28 days. Thus, based on percentage degradation, naphthalene-1,8 -diamine is considered to be not readily biodegradable in nature.

 

On the basis of above results for target chemical 2-methyl-4-nitroaniline (from OECD QSAR toolbox version 3.3 and EPI Suite, 2017) and for its read across substance (from authoritative database J-CHECK, 2016), it can be concluded that the test substance 2-methyl-4-nitroaniline 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  2-methyl-4-nitroaniline (CAS No. 99 -52 -5). If released in to the environment, 16.2% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of 2-methyl-4-nitroaniline in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the 2-methyl-4-nitroaniline is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of 2-methyl-4-nitroaniline 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 0.173%), indicates that 2-methyl-4-nitroaniline is not persistent in sediment.

Biodegradation in soil

The half-life period of test chemical 2-methyl-4-nitroaniline (CAS No. 99 -52 -5) 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, 83.5% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 2-methyl-4-nitroaniline in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 2-methyl-4-nitroaniline, 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 2 -methyl-4 -nitroaniline can be considered to be not readily biodegradable in nature.

Bioaccumulation: aquatic / sediment

Three predicted data from validated models for bioaccumulation (BCF) endpoint of target chemical 2-methyl-4-nitroaniline (Cas no. 99-52-5) were summarized as follows: 

 

First prediction using BCFBAF (v3.00) model and PBT profiler which indicate the estimated bio concentration factor (BCF) for 2-methyl-4-nitroaniline is 10 L/kg wet-wt which does not exceed the bioconcentration threshold of 2000.Thus it is concluded that 2-methyl-4-nitroaniline is not expected to bio accumulate in the aquatic environment.

 

Above prediction is supported by data from Scifinder database which suggest the Bioconcentration factor (BCF) for target chemical 2-methyl-4-nitroaniline was predicted to be 3.44 at pH range 1, 5.81 at pH 2, 6.24 at pH 3 and 6.30 at pH range 4-10 and temperature 25 deg.C. using the Scifinder database.Based on the BCF concentration at all range of pH it is concluded that the test chemical 2-methyl-4-nitroaniline is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

 

Further, Chemspider - ACD/PhysChem Suite prediction model indicate the Bioconcentration factor (BCF) for target chemical 2-methyl-4-nitroaniline was estimated to be 8.55 at pH 5.5 and 7.4 at temperature 25 deg.C. Based on the BCF concentration at two different pH concluded that the test chemical 2-methyl-4-nitroaniline is non bioaccumulative in nature as it does not exceed the BCF criteria of 2000.

Thus based on all available predicted reports for bioaccumulation endpoint concluded that the test substance 2-methyl-4-nitroaniline (Cas no. 99-52-5) is expected to be non Bioaccumulative in aquatic environment.

Adsorption / desorption

Four studies including experimental study and predicted data from validated models for adsorption (KOC) endpoint of target chemical 2-methyl-4-nitroaniline (Cas no. 99-52-5) were summarized as follows:

 

First study from experimental report by UERL laboratory; 2017 which suggest the adsorption coefficient Koc in soil and in sewage sludge 4-nitro-o-toluidine(CAS No.99-52-5) was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals. The reference substances were chosen according to functional group similarity with the test substance and calibration graph prepared. The reference substances were 4 -methylaniline, aniline, nitrobenzene, xylene, ethylbenzene and toluene, having Koc value ranging from 1.9 to 2.649. The Log Koc value was found to be 2.0875 ± 0.0002 at 25°C.

 

Above results also supported by prediction using KOCWIN model (v2.00) of EPI suite which indicated the adsorption value of 2-methyl-4-nitroaniline was estimated as Koc 178.6 L/kg (log Koc = 2.25) by means of MCI method at 25 deg.C. This Koc value indicates that the substance 2-methyl-4-nitroaniline has a low sorption to soil and sediment and therefore have moderate migration potential to groundwater.

 

Another prediction model i.e Chemspider - ACD/PhysChem Suite for target indicate the soil adsorption coefficient i.e Koc value of test substance 2-methyl-4-nitroaniline was estimated to be 161.70 (log koc: 2.20) at pH 5.5 and 7.4 and temp.25 deg.C Koc values at mentioned pH indicates that the substance 2-methyl-4-nitroaniline has slow sorption to soil and sediment and therefore have moderate migration potential to groundwater.

Last study from Scifinder database suggest the soil adsorption coefficient i.e Koc value of test substance 2-methyl-4-nitroaniline was estimated to be 71.0 (Log koc: 1.85) at pH 1, 120 (Log koc: 2.07)at pH 2 and  130 (Log koc:2.11) at pH 3-10 at temperature 25 deg.C. This Koc value at all range of pH condition indicates that the substance 2-methyl-4-nitroaniline has low sorption to soil and sediment and therefore have moderate migration potential to groundwater.

Thus all available studies for adsorption endpoint gives the common conclusion that the test substance 2-methyl-4-nitroaniline (Cas no. 99-52-5) is expected to have moderate mobility in soil and sediment compartment.