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Sediment toxicity

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Description of key information

No experimental data evaluating the toxicity to sediment organisms is available for fatty acids, C16-18 (even numbered), aluminum salts. Since the substance is ready biodegradable, chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate that fatty acids, C16-18 (even numbered), aluminum salts are not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the toxicity to sediment organisms is available for fatty acids, C16-18 (even numbered), aluminum salts. Since the substance is ready biodegradable, chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate that fatty acids, C16-18 (even numbered), aluminum salts are not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

 

Intrinsic properties and fate

Fatty acids, C16-18 (even numbered), aluminum salts are readily biodegradable (81% CO2 evolution after 29 days; OECD 301D, Peter Greven 2013). 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, 2008). 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 is poorly water soluble (< 0.15 mg/L). The log Koc value for the read-across substances palmitic acid and stearic acid are 4.1 and 4.7 respectively (KOCWIN v2.00 calculation). The Guidance on information requirements and chemical safety assessment, Chapter R7.B (ECHA, 2008) 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, 2008)) 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. Futhermore, aluminum is the most commonly occurring metallic element and comprises of 8% of earth crust (Salminen, 2005; Press and Siever, 1974), therefore it can be found in great abundance in the sediment and terrestrial environments. Concentrations of 3 -8% are common. The relative contribution of anthropogenic Al to the existing natural pools is very small and not relevant in terms of added amounts or in terms of toxicity. It can be concluded that the availability of fatty acids, C16-18 (even numbered), aluminum salts in the sedimentary environment is generally very low, which reduces the probability of chronic exposure of sediment organisms in general.

 

Aquatic ecotoxicity data

Short-term fish and invertebrates toxicity tests with the test substance, and additionally read-across data of the long term toxicity to fish, invertebrates and algae showed no adverse effects occurred up to the limit of water solubility (< 0.15 mg/L). The obtained results indicate that fatty acids, C16-18 (even numbered), aluminum salts are likely to show no toxicity to sediment organisms as well.

 

Metabolisms/Bioaccumulation

The substance fatty acids, C16-18 (even numbered), aluminium salts, is produced from natural fatty materials which is a mixture of stearic (C18) and palmitic (C16) acid. The substance consists of up to 90% natural fatty acid and up to 10% of aluminum. Fatty acids, C16 -18 (even numbered), aluminum salts, are present in water in dissociated form as different Al species and ionic fatty acid component. Due to the poor water solubility, the amount of dissolved Al will be very low (max. 5 μg/L). The fatty acid moiety is readily biodegradable and therefore it will undergo rapid and ultimate degradation in most environments. Besides, fatty acids are natural constituents of environment and are essential for a balanced nutrition of animals. Such compounds are naturally stored in the form of triacylglycerols primarily within fat tissue until they are used for energy production (fat storage tactic; Tocher, 2003). It is therefore considered that there will be no risk to aquatic organisms from potential bioconcentration/biomagnification of fatty acids. Experimental data available for a read-across substance aluminium sulfate confirm no potential for aluminium bioaccumulation/biomagnification in animals (BCF = 215).

 

Conclusion

Due to its readily biodegradable nature, extensive degradation of this substance 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, fatty acids, C16-18 (even numbered), aluminum salts will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. The supporting BCF values for fish determined experimentally for a read-across substance aluminium sulfate indicate that this substance will not be bioaccumulative (worst case BCF = 215). Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, fatty acids, C16-18 (even numbered), aluminum salts is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.

 

References:

ECHA. 2008a. Guidance on information requirements and chemical safety assessment – Part C: PBT assessment. European Chemicals Agency, Helsinki

ECHA. 2008b. Guidance on information requirements and chemical safety assessment – Chapter 7c: Endpoint specific guidance. European Chemicals Agency, Helsinki

Press F. and Siever R., 1974. Earth. WH Freeman and Co.

Salminen (ed.), 2005. Goechemical Atlas of Europe, Part 1. Background information, metodology and maps.

Tocher D. R., 2003., Metabolism and functions of lipids and fatty acids in Teleost fish. Reviews in Fisheries Science, 11(2), pp. 107 -184.