Triisotridecyl benzene-1,2,4-tricarboxylate

Sediment toxicity

Description of key information

Taking all available information into account the PFAE aromatic category members are unlikely to pose a risk for sediment organisms and testing is thus omitted

Additional information

No experimental data evaluating the toxicity to sediment organisms is available for the category PFAE aromatic. Since the members of the category are considered as enhanced ultimately biodegradable, chronic exposure of sediment organisms is unlikely. In addition, available data indicate, that the members of the PFAE aromatic categroy are not bioaccumulative and not toxic to aquatic organisms up to the limit of water solubility. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Intrinsic properties and fate/ exposure

The members of the PFAE aromatics category are considered to be enhanced ultimately biodegradable, and therefore, they can be expected to undergo ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs). Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment, where further biodegradation is expected.

Furthermore, the PFAE aromatic category members exhibit a log Koc value > 5 and are poorly water soluble (< 0.05 mg/L). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, (ECHA, 2012)) and the rest will be extensively biodegraded. Thus, discharged concentrations of these substances into the aqueous/sediment compartment are likely to be negligible.

Considering this one can assume that the availability of the PFAE aromatic category members in the sediment environment is very low, which reduces the probability of chronic exposure of sediment organisms in general.

Aquatic ecotoxicity data

The available short-term and long-term data of the PFAE aromatic category show no toxicity up to the limit of water solubility (WS < 0.05 mg/L) in all trophic levels. The results obtained indicate that the PFAE aromatic category members are likely to show no toxicity to sediment organisms as well.

Metabolism/Bioaccumulation

Bioaccumulation is not expected for members of the PFAE aromatic category. Based on the molecular weight (546-757 g/mol), size and structural complexity of the substances the uptake from medium into sediment organisms is considered to be low (e.g. Dimitrov et al., 2002). Absorbed molecules of the category members will be metabolized and the metabolites will be excreted (for details see IUCLID section 5.3). Additionally, for substances with a log Kow value > 10, which have been calculated for the members of the PFAE aromatic category, it is unlikely that they reach the pass level of being bioaccumulative according to OECD criteria for the PBT assessment (BCF > 2000 L/kg; ECHA, 2012).

Furthermore the BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation (BCF/BAF values of 0.89 L/kg and 0.89-10.92 L/kg, respectively), also indicate that this substance will not be bioaccumulative (all well below 2000 L/kg).

Conclusion

Due to their low water solubility, high adsorption potential and enhanced ultimate biodegradability, for all members of the PFAE aromatic category biodegradation in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Absorption of the PFAE aromatic category members is not expected due to the molecular weight (546-757 g/mol), size and structural complexity of the molecules. Absorbed molecules will be metabolized and the metabolites will be excreted. Therefore, the potential for bioaccumulation is low. Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, the PFAE aromatic category members are unlikely to pose a risk for sediment organisms in general and testing is thus omitted.