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Sediment toxicity

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Description of key information

No long-term toxicity test with sediment organisms is available, but no effects can be expected.

Key value for chemical safety assessment

Additional information

No long-term toxicity test with sediment organisms is available for Fatty acids, C16-18 and C18-unsaturated, branched and linear (CAS No. 68955-98-6), nevertheless no effects are to be expected, if exposure occurs. Fatty acids, C16-18 and C18-unsaturated, branched and linear (CAS No. 68955-98-6) has been shown to be readily biodegradable, hence it can be assumed that they will be completely biologically degraded within the sediment transport process. Although the log Kow (>4) suggests that adsorption to sediment is likely, fatty acids are used by sediment organisms as an energy source and for anabolic processes. Therefore, fatty acids are generally not considered to be toxic to sediment organisms. If used as an energy source microorganisms degrade the substance to carbon dioxide. In anabolic processes fatty acid carbon is incorporated into the biological matrix of the organism. The suitability as an energy source was demonstrated by ready biodegradability (OECD 301B) (Sewell, 1994). Hence, in case of exposure to sediment, the substance is expected to rapidly dissipate either by degradation or by integration into the organisms’ matrix. In addition due to the poor water solubility of the test substance it is expected to be within low concentrations in waste water, which will subsequently be eliminated in the sewage treatment plant (STP) as adsorption is mostly likely to occur to the sludge and hence any discharged effluent from the STP to the rivers, should, if at all, have insignificant or negligible quantities of the test substance.

 

This conclusion is also supported with data from sub-category 2 (predominantly oligomers) of the dimerised fatty acids and their derivatives, where one short-term study investing the toxicity with marine sediment organisms (Corophium sp.) to Fatty acids, C18-unsaturated, trimers (CAS No. 68937-90-6) (Staniland, 2005), is available. In this study, conducted according to OSPAR, Protocols on Methods for the Testing of Chemicals Used in the Offshore Oil Industry, over 10 days in natural sediment no effects were observed at 6095 mg/kg dry sediment and a LC50 of > 12187 mg/kg dry sediment is stated.

Thus one can conclude that in accordance with Regulation (EC) No 1907/2006, Annex X 9.5.1 column 2, a long-term toxicity to sediment organisms does not need to be conducted as the chemical safety assessment of this substance revealed no further need to investigate effects of the substance on sediment organisms as no toxicological effects on aquatic organisms were observed up to the limit of water solubility, secondly there is a the lack of chronic exposure and finally fatty acids are known to be easily metabolised and readily biodegradable.

 

 

References:

Staniland J. (2005). The toxicity to Corophium sp. of Radiacid 0980. Chemex Environmental. Report No. ENV7156/110416. Testing Laboratory: Chemex Environmental International Ltd, Bar Hill, Cambridge, CB3 8EL, England. Owner Company: Oleon nv.