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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Not considered as bioaccumulative, BCF < 2000

Key value for chemical safety assessment

Additional information

Concerning to the bioaccumulative potential reliable experimental data are not available.

The BCF was predicted with the BCF base-line model v.02.09 which is implemented in Catalogic v5.11.19. However, the compound is not within the applicability domain of the model. Its calculated logKow of 19.6 and molecular weight of 1180 Da are outside of the respective ranges of the training set. Only the calculated water solubility is within the training set range. The substance does not meet the general properties requirements. In regard to the structural fragment domain, 87.69% of the fragments could be found in correctly predicted training chemicals, only 12.31% are not present in the training chemicals. The substance is within the mechanistic domain of the model, i.e. the expected uptake mechanism is passive diffusion only. In summary, the substance is not within the applicability domain and the prediction falls in the extrapolation space. Although its reliability is low it is still acceptable in a weight of evidence approach. The logKow of CAS 6683-19-8 is 19.6. According to ECHA’s Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment, paragraph R.11.4.1.2, the aquatic BCF of a substance is probably lower than 2000 if the calculated logKow is higher than 10. Furthermore, the average maximum diameter of 25.6 Å is also indicative of a limited bioaccumulative potential. According to the above-mentioned guidance document the BCF for compounds with an average maximum diameter larger than 17 Å is probably less than 5000. Additionally, the molecular weight of 1180 g/mol is also an indicator that the BCF of the compound is lower than 2000. Taking these data into account CAS 6683-19-5 cannot be regarded as bioaccumulative. Its BCF value is assumed to be clearly below 2000.

This result is supported by the findings of available toxicity studies with mammals, which clearly demonstrated absence of systemic toxicity. The substance has not bioaccumulation potential and rapid excretion via the feces is expected (see also endpoint summary IUCLID section 7.1 Toxicokinetics, metabolism and distribution).

The same conclusion was derived by the ECB PBT working group assessment. CAS 6683-19-8 is not bioaccumulative and not very bioaccumulative. Seethe attached official PBT-Assessment No. 77 for the test substance by the European Commission Joint Research Centre (IUCLID section 13).

Furthermore, the bioaccumulation assessment with the same conclusion on the bioaccumulation potential is included in the examples in the "Guidance on information requirements and chemical safety assessment" (version 3.0, June 2017), Chapter R.11: PBT Assessment, Example R. 11-3.

 

Assessment of the bioaccumulation potential of the degradation products (identified with QSAR (Catalogic v5.11.19 BOD 28 days MITI (OECD 301C) v09.13 and identified in the official PBT-Assessment No. 77 for the test substance by the European Commission Joint Research Centre):

 

Metilox acid (CAS 20170-32-5)

Metilox acid was identified as the main metabolite in CATALOGIC 301C v.09.13. Furthermore, the assessment of the ECB PBT working group also identified metilox acid as one of the main metabolites according to the data on a structural analogue.

The bioaccumulative potential of metilox acid was assessed by the ECB PBT working group. Experimental BCF data on a close structural analogue (3-(3-tert-butyl-4-hydroxy-5-methyl-phenyl)-propionic acid revealed a BCF of <4.3. Another study performed by the Gakushuin University (1988) derived a BCF of 94-108 at high exposure concentration and 373-532 at the lower exposure concentration on metilox acid itself. Details can be found in the attached assessment of the ECB PBT working group.

In addition to the experimental data, a BCF was predicted with the BCF base-line model v.02.09. The corrected BCF was 13.5 L/kg. The compound was within the general parameter domain (logKow, molecular weight and water solubility) and the mechanistic domain. Concerning the structural fragment domain 86.67% of the compound’s fragments could be found in correctly predicted training chemicals. Only 13.33% of its fragments were unknown to the model. Therefore, the substance must be regarded as outside of the applicability domain. However, the model is regarded as reliable as the result clearly fits the experimental data.

In conclusion, all available data indicate a low bioaccumulative potential. Metilox acid does therefore not fulfill the B/vB criteria and thus not the PBT/vPvB criteria.

Pentaerythritol (CAS 115-77-5)

Pentaerythritol was identified by the ECB PBT working group as major metabolite of CAS 6683-19-8. It was also identified by Catalogic 301C, however the quantity was below 0.1% mol/mol parent as it was predicted to be subject of further degradation. The logKow was predicted with Catalogic 301C was -1.77 and does not fulfil the screening criteria for bioaccumulative or very bioaccumulative according to Annex XIII of Regulation (EC) No 1907/2006.

According to the experimental data the compound is not bioaccumulative with an experimental BCF range of only 0.3-2.1 (cf. assessment of ECB PBT working group and OECD SIDS in IUCLI chapter 13.). Therefore, the bioaccumulation potential of pentaerythritol is very low. As a consequence, pentaerythritol is not further assessed and not included in the table below.

Further metabolites identified with CATALOGIC 301C

Relevant metabolites and information on BOD, BCF, logKow and DiamMax average can be found in the table. In general, the identified metabolites consist of pentaerythritol as a core and 2 to 4 metilox acid groups (in some cases slightly modified at the tert butyl group or the propane chain) attached to it. In dependence of the amount of metilox groups the logKow values range from 7.02 to 18.06.In the absence of experimental data on the degradability and bioaccumulation the CATALOGIC 301C v.09.13 and BCF base-line model v.02.09 were used to predict the BOD and the BCF.

Regarding the bioaccumulative potential the BCF of the metabolites was predicted as <10 in the BCF base-line model v.02.09. Furthermore, the larger metabolites exhibit very high logKow values >10 which is indicative of a BCF value <2000. The DiamMax average was also taken into account. It ranges from 21.4 to 25.1Å which is clearly indicative of a hindered uptake. According to ECHA’s Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT/vPvB assessment, paragraph R.11.4.1.2 substances with a Dmax-aver larger than 17Å have BCF values <5000. The respective metabolites clearly exceed this threshold. In regard to the applicability domain, the metabolites are within the mechanistic domain, i.e. they are taken up by passive diffusion only. The larger metabolites are outside of the parameter ranges due to their high logKow values and molecular weights. The smaller ones are within the parameter ranges. Concerning the structural domain, the compounds share 86 to 89% of correctly predicted fragments of the training set. Consequently, only 11 to 14% of the fragments were unknown. Despite the overall outcome that the compounds are outside of the applicability domain, the predictions of the BCF are regarded as reliable and suitable in a weight of evidence approach together with data on logKow and DiamMax-aver.

Taking all lines of evidence into account, none of the metabolites can be regarded as bioaccumulative.

Parent and metabolites at a quantity ≥0.1% (mol/mol parent) and a logKow ≥4.

Quantity [% mol/mol parent](1)

LogKow(1,2)

BOD Catalogic [%](1)

BCF Catalogic(2)

DiamMax Average [Å](2)

Molecular weight

[g/mo])

Remarks

SMILES Code

4.01

19.60

2.00

7.4

25.6

1180

Parent (CAS 6683-19-8)

CC(C)(C)c1cc(CCC(=O)OCC(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

230.20

4.77

0.00

13.5

12.4

278

Metabolite No 1 (Metilox acid; CAS 20170-32-5)

CC(C)(C)c1cc(CCC(O)=O)cc(C(C)(C)C)c1O

10.38

13.91

2.00

7.4

23.7

917

Metabolite No 2 (triester)

CC(C)(C)c1cc(CCC(=O)OCC(CO)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

0.37

18.06

2.00

7.4

25.1

1190

Metabolite No 3

CC(C)(C)c1cc(CCC(=O)OCC(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CC(O)c2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

24.37

8.62

2.00

6.9

22.3

657

Metabolite No 4 (diester)

CC(C)(C)c1cc(CCC(=O)OCC(CO)(CO)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

0.51

12.77

2.00

7.4

23.6

933

Metabolite No 5

CC(C)(C)c1cc(CCC(=O)OCC(CO)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CC(O)c2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

0.73

18.00

2.00

7.4

25.0

1210

Metabolite No 6

CC(C)(C)c1cc(CCC(=O)OCC(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C(O)=O)c1O

2.38

7.08

2.00

6.3

21.4

673

Metabolite No 7

CC(C)(C)c1cc(CCC(=O)OCC(CO)(CO)COC(=O)CC(O)c2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C)c1O

1.03

12.30

2.00

7.4

23.2

947

Metabolite No 8

CC(C)(C)c1cc(CCC(=O)OCC(CO)(COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C(O)=O)c1O

4.76

7.02

2.00

6.3

21.5

687

Metabolite No 9

CC(C)(C)c1cc(CCC(=O)OCC(CO)(CO)COC(=O)CCc2cc(C(C)(C)C)c(O)c(C(C)(C)C)c2)cc(C(C)(C)C(O)=O)c1O

(1)Catalogic v5.11.19, CATALOGIC 301C v.09.13

(2)Catalogic v5.11.19, BCF base-line model v.02.09

QSAR disclaimer:

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore, according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

For the assessment of the substance and its degradation products (Q)SAR results were used for determination of the bioaccumulation potential. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.

 

Therefore, and for reasons of animal welfare, further experimental studies on bioaccumulation are not provided.