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Classification & Labelling & PBT assessment

PBT assessment

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Administrative data

PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB

Classification of Disodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4-yl]azo]-2-hydroxybenzene-1-sulphonato(4-)]hydroxychromate(2-) for effects in the environment:


The chemicalDisodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4-yl]azo]-2-hydroxybenzene-1-sulphonato(4-)]hydroxychromate(2-)(CAS no. 6408-31-7) is used as a dyestuff for wool and leather as well as in adsorption and dye recovery studies. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled forDisodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4-yl]azo]-2-hydroxybenzene-1-sulphonato(4-)]hydroxychromate(2-). The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.


Persistence assessment


The tested substance fulfils the P criterion within Annex XIII based on the assessment that here follows:

Biotic degradation

In an experimental key study from peer reviewed journal (U. Pagga and O. Brown, 1986), biodegradation experiment was carried out for 42 days for evaluating the percentage biodegradation of the test chemical Disodium [5 -chloro-3 -[[4,5 -dihydro-3 -methyl-5 -oxo-1 -(3 -sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) (CAS no. 6408 -31 -7) 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 the test substance Disodium [5 -chloro-3 -[[4,5 -dihydro-3 -methyl-5 -oxo-1 -(3 -sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) was determined to be 28% by using DOC removal parameter in 42 days. Thus, based on percentage degradation, the chemical Disodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) was considered to be not readily biodegradable in nature.

Another biodegradation study was conducted for 48 hrs for evaluating the percentage biodegradability of test substance Disodium [5 -chloro-3 -[[4,5 -dihydro-3 -methyl-5 -oxo-1 -(3 -sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) (CAS no. 6408 -31 -7) by using different species of Pseudomonas under anaerobic conditions at a temperature of 28°C (ForP. oleovorans and P. putida) and 37°C (For P. aeruginosa), respectively (E. Silveira, et. al; 2009).  Pseudomonas aeruginosa, Pseudomonas oleovorsans and Pseudomonas putida were used as a test inoculum for the study. 4 different Pseudomonas spp. were screened before using for the decolorization study. As all samples contained biomass and dye, concentration of biomass (first and second step) and dye (third step) were evaluated. Control experiments were performed using the same medium without microorganisms or dyes. Methyl orange was used as a standard dye for the study. P. aeruginosa achieved the highest colour removal rate, removing over 97% of the colour from the standard dye (methyl orange). The percentage decolourization of test substance Disodium [5 -chloro-3 -[[4,5 -dihydro-3 -methyl-5 -oxo-1 -(3 -sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) was determined to be 52% and approx. 15% by using three different strains i.e;Pseudomonas aeruginosa, Pseudomonas oleovorsans and Pseudomonas putidaafter 48 hrs. Thus, based on percentage decolorization, Disodium [5 -chloro-3 -[[4,5 -dihydro-3 -methyl-5 -oxo-1 -(3 -sulphophenyl)-1H-pyrazol-4 -yl]azo]-2 -hydroxybenzene-1 -sulphonato(4 -)]hydroxychromate(2 -) is considered to undergoes primary degradation in water and thus can be expected to be biodegradable in nature

The experimental studies for the similar substances (CAS: 1934-21-0) also indicate that it is not readily biodegradable.

Hence, it has been concluded thatDisodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4-yl]azo]-2-hydroxybenzene-1-sulphonato(4-)]hydroxychromate(2-)is likely to be persistent (P) in nature.



Bioaccumulation: aquatic/sediment

The tested substance fulfils the B criterion within Annex XIII based on the assessment that here follows:


Theoctanol water partition coefficient of the test chemical is 4.65 which is slightly more than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a moderate risk for the chemical to bioaccumulate in fish and food chains.



The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:


The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).


Aquatic organisms

All of the available short-term eco-toxicity estimations for invertebrates and algae for the substance indicates the LC50/EC50 value to be > 100 mg/L. These value suggest that the substance is likely to be non-hazardous to Aquatic organisms at environmentally relevant concentrations and can be considered as not classified as per the CLP regulation.


There are no long-term toxicity evaluation available forDisodium [5-chloro-3-[[4,5-dihydro-3-methyl-5-oxo-1-(3-sulphophenyl)-1H-pyrazol-4-yl]azo]-2-hydroxybenzene-1-sulphonato(4-)]hydroxychromate(2-). By speculation, long-term NOEC for aquatic organisms cannot be expected for the substance at concentration below 0.01 mg/L based on the data mentioned above.


The chemical was therefore considered as non-hazardous to aquatic environments as per the criteria set out in Annex XIII.



Based on critical, independent and collective evaluation of information summarized herein, the tested compound fulfils the P and B criterion but does not fulfil the T criterion and has therefore not been classified as a PBT compound within Annex XIII