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Sediment toxicity

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Description of key information

The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the effects on sediment organisms.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the toxicity to sediment organisms is available. Since the substance is readily biodegradable, chronic exposure of sediment organisms is unlikely. Furthermore, Propyleneglycole dioleate (CAS 105-62-4) is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that the substance is not bioaccumlative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

 

Intrinsic properties and fate

The substance is readily biodegradable based on data from accepted OECD guidance. According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b, readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs) (ECHA, 2012). Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment.

 

Furthermore, the substance exhibits a log Koc of > 5 (MCI) and is 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 (due to ready biodegradability). 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 Propyleneglycole dioleate (CAS 105-62-4) in the sediment environment is very low, which reduces the probability of chronic exposure of sediment organisms in general.

 

Aquatic ecotoxicity data

Acute aquatic toxicity tests of the substance to fish, invertebrates, algae and microorganisms showed no adverse effects occurred up to the limit of water solubility. The obtained results indicate that it is likely that there is no toxicity to sediment organisms as well.

 

Metabolisms/Bioaccumulation

After absorption glycol esters are expected to be enzymatically hydrolyzed by carboxylesterases yielding the corresponding alcohol and fatty acid. The substance is characterized by a high log Kow indicating a potential for bioaccumulation. But due to the low water solubility, rapid environmental biodegradation and metabolisation via enzymatic hydrolysis, a relevant uptake and bioaccumulation in aquatic organisms is not expected. Enzymatic breakdown will initially lead to the free fatty acid and the free glycol alcohol (e. g. propylene glycol). From literature it is well known, that these hydrolysis products will be metabolized and excreted in fish effectively (Heymann, 1980; Lech & Bend, 1980; Lech & Melancon, 1980; Murphy & Lutenske, 1990). This is supported by a low calculated BCF value of 0.893 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic). Thus, taking all information into account, the bioaccumulation of Propyleneglycole dioleate (CAS 105-62-4) is assumed to be low.

 

Conclusion

Due to its readily biodegradable nature, extensive degradation of Propyleneglycole dioleate (CAS 105-62-4) in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment, further biodegradation will occur and, due to the high log Kow, low water solubility and high adsorption potential, the substance will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. After uptake by sediment species, extensive and fast biotransformation by carboxylesterases into the free fatty acid and the corresponding alcohol is expected. The supporting BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, also indicate that Propyleneglycole dioleate (CAS 105-62-4) will not be bioaccumulative. Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, Propyleneglycole dioleate (CAS 105-62-4) is unlikely to pose a risk for sediment organisms.