4-nitro-o-toluidine

Endpoint summary

Description of key information

Short-term toxicity to fish

Acute fish toxicity was conducted for 2-methyl-4-nitroaniline. The median ethal concentration (LC50) on the basis of mortality effect for Pimephales promelas (Fathead Minnow) was observed to be 86.7 mg/l for exposure period of 96 hrs.

Short term toxicity on aquatic invertebrates

Based on the prediction done using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the six closest read across substances, the short term toxicity on aquatic invertebrates was predicted for2-methyl-4-nitroaniline (99-52-5). EC50 value was estimated to be 4.18 mg/l for Daphnia magna for 48 hrs duration. Based on the value, the chemical was considered to be toxic to aquatic invertebrates and can be considered to be classified in chronic category 2 as per the CLP regulations.

Toxicity to aquatic algae and cyanobacteria

The effect of test item 4-nitro-o-toluidine, CAS No. 99-52-5 was studied on the growth of fresh water green alga Chlorella vulgaris (UERL study report, Sustainability Support Services (Europe) AB, 2017). The study was conducted following OECD guideline 201 - Alga, growth inhibition test. The test concentration chosen for the study were 0.5 mg/L,1 mg/L, 2mg/L, 4 mg/L, 8 mg/L,16 mg/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 1.503 mg/L.Thus based on this value, it can be concluded that the substance can be considered as toxic to aquatic organisms and thus can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

Toxicity to microorganisms

QSTR Study on Aquatic Toxicity Against Tetrahymena pyriformis using Topological Indices for chemical 2-methyl-4-nitroaniline (Cas no.99-52-5) indicate that the toxicity data as 50% growth inhibitory concentration (log 1/IGC50 = pIGC50) against micro organism species Tetrahymena pyriformis was estimate to be 1/log IGC50 =2.04 which is equivalent to 109.64 mg/l.

Additional information

Short-term toxicity to fish

Acute fish toxicity was conducted for 2-methyl-4-nitroaniline for exposure period of 96 hrs. Test organism was used as Pimephales promelas (Fathead Minnow)in static freshwater with test temp. 20.3 (19.5-22.0) deg.C ,hardness 29.6 (12.0- 43.0)mg/L CaCO3 ,pH7.6 (6.0- 9.2) , ALKALINITY:31.0 (15 - 60) mg/L CaCO3 ,conductivity 66.8 uS and dissolved oxygen 7.2 (2.8-9.4) mg/L. The median ethal concentration (LC50) on the basis of mortality effect for Pimephales promelas (Fathead Minnow) was observed to be 86.7 mg/l for exposure period of 96 hrs. Based on the value, the chemical was considered to be toxic to fish and can be considered to be classified in chronic category 3 as per the CLP regulation.

Short term toxicity to aquatic invertebrates

Short term toxicity to aquatic invertebrates for 2-methyl-4-nitroaniline (99-52-5)was summarised with one predicted data and two experimental studies of two functionally related read across substances are as follows:

Based on the prediction done using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the six closest read across substances, the short term toxicity on aquatic invertebrates was predicted for2-methyl-4-nitroaniline (99-52-5). EC50 value was estimated to be 4.18 mg/l for Daphnia magna for 48 hrs duration. Based on the value, the chemical was considered to be toxic to aquatic invertebrates and can be considered to be classified in chronic category 2 as per the CLP regulations.

Study was performed in Daphnia magna from Ecotox database, 2016 for two read across substances 5-methyl-2-nitroaniline (578-46-1) and 2-methyl-3,6-dinitroaniline(56207-39-7).

The test was performed in static fresh water system with different test conditions. After 48 hrs, the EC 50 value for 5-methyl-2-nitroaniline (578-46-1) was determined to be 5.8 mg/l and the EC50 value for 2-methyl-3,6-dinitroaniline was determined to be 2.2 mg/l. Based on the value, the chemical was considered to be toxic to aquatic invertebrates and can be considered to be classified in aquatic chronic 2 category as per the CLP regulations.

Based on the above predicted data and studies of functionally related read across chemicals it can be considered that all the above studies supported the target classification, and thus 2-methyl-4-nitroaniline (99-52-5) was likely to be toxic to aquatic invertebrates and can be considered to be classified in aquatic chronic 2 as per the CLP regulations.

Toxicity to aquatic algae and cyanobacteria

Various experimental key and supporting studies for the target compound 2 -methyl-4 -nitroaniline (CAS No. 99 -52 -5) were reviewed to summarize the following information:

 

In an experimental key study, the effect of test item 4-nitro-o-toluidine, CAS No. 99-52-5 was studied on the growth of fresh water green alga Chlorella vulgaris (UERL study report, Sustainability Support Services (Europe) AB, 2017). The study was conducted following OECD guideline 201 - Alga, growth inhibition test. The test concentration chosen for the study were 0.5 mg/L,1 mg/L, 2mg/L, 4 mg/L, 8 mg/L,16 mg/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 1.503 mg/L.Thus based on this value, it can be concluded that the substance can be considered as toxic to aquatic organisms and thus can be considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

 

In a supporting study from peer reviewed journal(Janet Riedl et. al; 2007), short term toxicity to Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) study was carried out for 72 hrs. The study was performed according to OECD Guideline 201 (Alga, Growth Inhibition Test) and other method ISO 8692, respectively. The study was based on the effects of the test compound 2 -methyl-4 -nitroaniline (CAS no. 99 -52 -5) on Desmodesmus subspicatus in a static fresh water system at a temperature of 23 ± 2°C and pH of 6.9 ± 0.2, respectively. Test chemical concentration used for the study was 1000 mg/l (0.1%). Test solution was prepared by dissolving the chemical 2 -methyl-4 -nitroaniline in DMSO.Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) was used as a test organism. Stock culture and pre-culture were prepared according to OECD Guideline 201 (Alga, Growth Inhibition Test). Liquid cultures of the unicellular green algae Desmodesmus subspicatus (formerly known as Scenedesmus subspicatus) were grown photoautotrophically at 23 ± 2°C in an inorganic, sterilized medium with an additive of 1.5 mM NaHCO3 providing a final pH of the medium of 6.9 ± 0.2. Algae were incubated in a climatic chamber (HB 0714, Heraeus, under continuous light conditions from two types of fluorescent light tubes (L30W/830 Warmwhiteand L30W/77) providinga photosynthetic active radiation of 300 ± 20µE s-1m-2. The test was conducted in transparent microplates with 24 wells with an initial cell density of 5 × 103cells/ml, sealed with Parafilm M to minimize evaporation and shaken in intervals of 4 min with 100 rpm and 1 min pause. Incubation conditions were the same as used for cultivation. Compounds were tested on individual plates with 6 growth controls, 2 blank values without sample and inoculum and 16 sample concentrations. The growth inhibition was calculated by normalizing the data to the results of control cultures. Effect parameter population growth was determined by measuring the chlorophyll a content fluorometrically (SpectraMax Gemini EM, Molecular Devices, Sunnyvale, USA) after 0, 24, 48 and 72 h with an excitation wave length of 430 nm, emission of 690 nm and a cut-off filter <665 nm, evaluated with SoftMax Pro 3.1.1.The EC50 value of a compound was estimated by acquiring the best-fit concentration – response relationship using two fundamentally different models, namely either the Hill or the Weibull model, respectively. The concentration in the test vessels after an incubation time of 30 min and 72 h was verified by high performance liquid chromatography analysis. A 5lm particle size, reversed-phase C8 column (Lichrospher 60 RP select B, Merck, Darmstadt, Germany) was used as a stationary phase, the mobile phase was made up of methanol: water (40:60). The change in concentration over 72 h was analysed in bidistilled water, growth medium and algal suspension. Algae were centrifuged from the suspension before analysis. In principle, for each substance one concentration close to the EC50 value was investigated. For 2 -methyl-4 -nitroaniline no relevant loss of substance over the testing time could be determined (loss in exposure concentration of-0.7%). Based on effect on growth rate of the test organism Desmodesmus subspicatus, the 72 hr EC50 value was determined to be 9.7 mg/l, respectively. Thus, based on the EC50 value, it can be concluded that the substance 2 -methyl-4 -nitroaniline can be considered as toxic to aquatic organisms and thus can considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

 

Thus, based on the overall reported results for target chemical 2-methyl-4-nitroaniline (fromUERL study reportand peer reviewed journal), it can be concluded that the test substance 2 -methyl-4 -nitroaniline can be considered as toxic to aquatic organisms and thus can considered to be classified in aquatic chronic category 2 as per the CLP classification criteria.

Toxicity to microorganisms

QSTR Study on Aquatic Toxicity Against Tetrahymena pyriformis using Topological Indices for chemical 2-methyl-4-nitroaniline (Cas no.99-52-5) indicate that the toxicity data as 50% growth inhibitory concentration (log 1/IGC50 = pIGC50) against micro organism species Tetrahymena pyriformis was estimate to be 1/log IGC50 =2.04 which is equivalent to 109.64 mg/l.This estimated IGC50 value suggest that chemical 2-methyl-4-nitroaniline (Cas no.99-52-5) may not have toxicity concern to micro organism Tetrahymena pyriformis.