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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 1-[(2-methoxyphenyl)azo]-2-naphthol for effects in the environment:


The chemical 1-[(2-methoxyphenyl)azo]-2-naphthol (CAS no. 1229-55-6) is used in the dyestuff industry. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for 1-[(2-methoxyphenyl)azo]-2-naphthol. 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 does not fulfil the P criterion within Annex XIII based on the assessment that here follows:


Environmental fate

Biodegradation in water and sediment study was carried out for determining the half-life of test chemical 1-[(2-methoxyphenyl)azo]-2-naphthol (CAS no 1229 -55 -6) under anaerobic conditions (George L. Baughman and Eric J. Weber, 1994). Sediments were obtained from 2 different lakes (i.e, Herrick and Kingfisher) near Athens, GA. The sieved sediment (5-15 cm deep) was stored in the dark, under lake water, in sealed, 2-gal glass or plastic bottles until used. The desired amount of sediment (based on wet weight and moisture content of filter cake) in lake water was sealed and allowed to remain quiescent for 2-4 days prior to dye addition. During dye addition (in ACN) and mixing, the sediment was maintained under N2 until placement in 20-mL scintillation vials. No attempt was made to measure redox potentials in the compacted sediment of either kinetic or product studies. However, under the study conditions, the reddish Georgia clay sediment quickly became the light gray color that is characteristic of reducing environments.Vials were sacrificed for analysis by shaking, sonicating, and filtering..Test chemical was identified by analytical methods such as HPLC and GC. Products of the azo dye, SR 1, were expected to be o-anisidine and l-amino-2-naphthol resulting from reductive cleavage of the azo bond. However, these compounds could not be identified by HPLC because they coeluted. After GPC cleanup, each product was detected by GC-MS with both spectra and retention times identical to those of purchased materials.The half-life value of test chemical 1-[(2-methoxyphenyl)azo]-2-naphthol in sediment obtained from2 different lakes (i.e, Herrick and Kingfisher) was determined to be 4.0 and 2.2 days with an average first order rate constant of 7.2 × 10-3and 1.3 × 10-2, respectively. Based on this half-life value, it indicates that 1 -[(2 -methoxyphenyl)diazenyl]-2 -naphthol is not persistent in sediment.


The half-life period of 1-[(2-methoxyphenyl)diazenyl]-2-naphthol (CAS No. 1229 -55 -6) 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, 74.9% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of 1-[(2-methoxyphenyl)diazenyl]-2-naphthol in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of 1-[(2-methoxyphenyl)diazenyl]-2-naphthol, 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.


Hence it has been concluded that 1-[(2-methoxyphenyl)azo]-2-naphthol is not persistent in nature.  



Bioaccumulation assessment

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


The BCF of oil pink i.e 1-[(2-methoxyphenyl)azo]-2-naphthol in aquatic organisms was reported as 290000 using a measured log Kow of 7.5 and a recommended regression-derived equation. This BCF value indicates that bioconcentration in aquatic organisms will be an important fate process i.e chemical have concern for bioaccumulation in aquatic environment.

Although the BCF values derived using a regression-derived equation suggest classification of the substance as very Bioaccumulative (vB), it is classified only as Bioaccumulative (B) due to lack of experimental data since only estimated values are available.



Toxicity assessment

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


As per Column 2 (Annex VII and VIII) of the REACH regulation, a study does not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur for instance if the substance is highly insoluble in water (solubility: 0.00033mg/L). The chemical was therefore not considered as 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 B criterion but does not fulfil the P and T criterion and has therefore not been classified as a PBT compound within Annex XIII.