2,6-diisopropylnaphthalene

PBT assessment

PBT assessment: overall result

Reference

Name:

2,6-Diisopropylnaphthalene

Type of composition:

boundary composition of the substance

State / form:

solid: bulk

>= 90 - <= 99.9 % (w/w)

Reference substance:

2,6-Diisopropylnaphthalene

Reference substance:

2,6-Diisopropylnaphthalene

This impurity is considered relevant for the classification and labelling of the substance

PBT status:

the substance is not PBT / vPvB

Justification:

Persistence Assessment

No biodegradation study concerning only 2,6-diisopropylnaphthalene (2,6-DIPN) is available. Bis(isopropyl)naphthalene (DIPN) is an isomeric mixture, which consist of seven isomers (1,3-, 1,4-, 1,5-, 1,6-, 2,6- and 2,7-DIPN). In a sealed vessel CO2 headspace test using 14C ring labelled diisopropylnaphthalene isomer mixture, no ultimate biodegradation could be demonstrated. Analysing DIPN content in test medium, mean primary biodegradation (ca. 20 - 25%) was observed, while the degree of primary degradation was ~100% after 28 days for 2,6-DIPN. On the other hand, ultimate degradation could not be concluded for the target substance, 2,6-DIPN.

Therefore 2,6-diisopropylnaphthalene (CAS: 24157-81-1; 2,6-DIPN) needs to be assessed as potentially persistent (P) and/or very persistent (vP).

 

Bioaccumulation Assessment

No bioaccumulation study concerning only 2,6-diisopropylnaphthalene (2,6-DIPN) was available. But a GLP study according to OECD 305 examining the bioaccumulative potential of Bis(isopropyl)naphthalene (DIPN), an isomeric mixture which consist of seven isomers (1,3-, 1,4-, 1,5-, 1,6-, 2,6- and 2,7-DIPN) is available and used in a read-across approach. In this study the BCF values of the seven isomers was determined individually for each isomer. The determined BCF values differed strongly between the isomers.

According to the recent OECD 305 (2012) as well as the ECHA Guidance Document R.11 (v2.0, 2014), the BCF values should be expressed based on a 5% lipid content. In the original study report the BCF data were not lipid-normalised. Therefore, in an expert statement by ECT Oekotoxikologie GmbH (ETC, 2017) a lipid-normalisation was performed using the data (BCF and lipid content) available in the original study report.

For 2,6-DIPN the lipid normalized BCF values were determined as 810 (low dose group; 0.47 µg/L) and 2200 (high dose group; 4.85 µg/L), respectively. Hence, 2,6-DIPN fulfils the criterion of being bioaccumualtive (BCF > 2000) but not very bioaccumulative (BCF < 5000).

Although the environmental relevance of the results from the high exposure concentration is questionable (see expert statement ETCECT, 2017) the highest measured BCF value of 2200 was used as an worst case assumption for the bioaccumulation assessment. Therefore, 2,6-diisopropylnaphthalene (CAS24157-81-1)DIPN was assessed as bioaccumulative (B) but not very bioaccumulative (vB) under environmental conditions.

Toxicity Assessment

No chronic ecotoxicological study concerning only 2,6-diisopropylnaphthalene (2,6-DIPN) is available. But a long-term toxicity study on Daphnia magna following OECD guideline 211 examining Bis(isopropyl)naphthalene (DIPN), an isomeric mixture which consist of seven isomers (1,3-, 1,4-, 1,5-, 1,6-, 2,6- and 2,7-DIPN) is available and used in a read-across approach. In this study a NOEC (21 d) of 0.0118 mg/L (measured, TWA) based on the reproduction rate was determined. This result should be used as a worst-case since 1,3- and 1,4-DIPN were identified by ECHA as the most critical isomers with regards to aquatic toxicity. Even individual studies with those critical isomers resulted in effect concentrations above the trigger meeting the T-criterion. Based on further available data, the substance2,6-DIPN is not classified as carcinogenic (category 1A or 1B), germ cell mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B or 2) according to Regulation (EC) No 1272/2008. Hence, the T T-criterion is not fulfilled.

 

In conclusion, the substance the substance is not a PBT or a vPvB substance.