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Bioaccumulation: aquatic / sediment

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Description of key information

A weight-of-evidence approach using experimentally determined BCF values of max. 47, several QSAR estimations and taking molecular dimensions of Tinuvin 123 into account demonstrates that the substance does not significantly accumulate in organisms.

Key value for chemical safety assessment

Additional information

In a weight of evidence approach, an OECD 305C as well as several QSAR models were used to assess the potential of Tinuvin 123 to bioaccumulate in organisms.

In a GLP guideline study conducted in compliance with OECD 305C, the test fish (Cyprinuscarpio) were continously exposed to concentrations of 0.025 mg/l and 0.0025 mg/l, respectively, of 14C-labeled test material. A dispersant (HCO-30) was used to prepare the test solutions. Concentrations of the test substance in water and fish body were measured using a liquid scintillation counter.

The test was terminated after 8 weeks of exposure. For test fish exposed to 0.025 mg/l, a BCF of 32 - 46 was determined, whereas at the test concentration of 0.0025 mg/l, a BCF of 43 – 47 was observed.

A supporting study was performed with Cyprinuscarpio according to "Study Methods Concerning New Chemical Substances: The Test on the Degree of Bioconcentration in Fish and Shellfish (Kanpogyo No.5, Yakuhatsu No.615, 49-Kikyoku No.392, 1974)" which is equivalent to OECD Guideline 305 C. The fish were exposed to concentrations of 1 mg/l and 0.1 mg/l for a test period of 8 weeks in a flow-through system. A BCF < 4.6 was determined for the test concentration 1 mg/l. At a concentration of 0.1 mg/l the BCF ranged from 4.5 - < 35.

To further contribute to the weight of evidence, a series of QSAR estimations were performed to estimate the bioaccumation potential of Tinuvin 123. SMILES codes of the two compounds of Tinuvin 123 were used to calculate the following log KOW values:

 

 

compound 1

compound 2

SMILES

CCCCCCCCON1C(CC(CC1(C)C)OC(=O)CCCCCCCCC(=O)OC2CC(N(C(C2)(C)C)OCCCCCCCC)(C)C)(C)C

CCCCCCCCON1C(CC(CC1(C)C)OC(=O)CCCCCCCCC(=O)OC2CC(N(C(C2)(C)C)OCCCCCCCCON3C(CC(CC3(C)C)OC(=O)CCCCCCCCC(=O)OC4CC(N(C(C4)(C)C)OCCCCCCCC)(C)C)(C)C)(C)C)(C)C

Log KOW KOWWIN Program (v1.68)

14.27

24.27

Log D
SPARC

13.45

Input to model did not return meaningful result

Log KOW Catalogic

14.269

24.267

 

SMILES codes and/or estimated log KOW values were used as input parameters for several tools to estimate the bioaccumulation potential of Tinuvin 123.

Models taking into account the log KOW only were hardly applicable because the log KOW of Tinuvin 123 is not within the range of the single models (see UBA models: Müller & Nendza, 2011).

Since bioaccumulation is also influenced by other factors than the log KOW, the CATALOGIC v5.11.2 BCF model takes several mitigating factors into consideration when deriving the BCF. According to the output, the most important mitigating factor of the two Tinuvin 123 compounds is the low water solubility. In total – and taking mitigating factors into account – the BCF was estimated to be 7.43 for both compounds.

According to the BCFBAF v3.01 model of EPI Suite v4.10, the BCF for compound 1 is 3.651 and 3.162 for compound 2, respectively.

The VEGA BCF models (CAESAR; v2.1.11, Meylan v1.0.0, Read-Across v1.0.0) predict BCFs for the two compounds in the range of 0.75 to 121. However the reliability of the calculation is low as the two molecules are not clearly within the model's applicability domain.

The US EPA TEST package calculates the BCF on different sets of molecular descriptors. According to this strategy, the compounds yielded BCF values of 2.68 and 1.43 using the consensus method.

Molecular dimensions as indicators for limited bioconcentration, i. e. average maximum diameter were assessed as well. According to ECHA's Guidance on Information Requirements and Chemical Safety Assessment, R.11: PBT Assessment, the capability of crossing biological membranes is hindered if the average maximum diameter is > 1.7 nm. The compounds of Tinuvin 123 have a minimum DiamMax of 18.6 and 28.5 nm, respectively.

In conclusion, using all available data in a weight-of-evidence approach, significant accumulation of Tinuvin 123 in organisms is not to be expected.