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Sediment toxicity

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Description of key information

10d-LC50 = 3367.41 mg/kg dw sediment for Corophium volutator (OSPARCOM)

Key value for chemical safety assessment

Additional information

No data investigating the toxicity of Fatty acids C16-18, methyl esters (CAS No. 85586-21-6) to sediment organisms are available. Therefore, toxicity data from a structurally related analogue substance, Fatty acids C16-18 and C18 unsaturated, methyl esters (CAS No. 67762-38-3) is used as read-across in accordance with Regulation (EC) No.1907/2006, Annex XI, 1.5. Both substances are fatty acids esterified with methanol, containing fatty acid C-chain lengths of C16-18 (saturated and unsaturated in the case of CAS No. 67762-38-3). Furthermore, their log Pow (> 5) and water solubility values (< 0.05 and < 1 mg/L for Fatty acids C16-18 and C18 unsaturated, methyl esters and Fatty acids C16-18, methyl esters, respectively) indicate that once released into the water phase, both substances will tend to bind to sediment and other organic particles. Considering the structural similarity and comparable behavior in the water/sediment phase, using sediment toxicity data from Fatty acids, C16-18 and C18 unsaturated as read-across for Fatty acids, C16-18, methyl esters is justified in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5.

One study evaluating the toxicity of Fatty acids, C16-18 and C18 unsaturated (CAS No. 67762-38-3) to a marine sediment organism is available (Hudson, 1999). This test was conducted according to the OSPARCOM Guideline, Sediment bioassay using an amphipodCorophiumsp., under GLP conditions.Corophium volutator(20 organisms per replicate) was exposed to the test substance in natural sediment for a period of 10 days. Nearly complete mortality was reported at the highest concentration tested (16,011.13 mg/kg dw, nominal) after the exposure period, whereas no significant effects were observed in any of the other treatment groups (17.38-1707.82 mg/kg dw, nominal). The resulting 10d-LC50 was 3367.41 mg/kg sediment dw.

Fatty acids, C16-C18, methyl esters (CAS No. 85586-21-6) is a readily biodegradable and poorly soluble substance (< 1 mg/L). Due to these characteristics, extensive biodegradation and adsorption to activated sludge within conventional STPs can be expected and therefore, only low concentrations are likely to be released into the water phase and directly bioavailable to sediment organisms. Considering the expected low concentrations of the substance in the water/sediment phase and the results of the 10-day test performed on the analogue substance (showing only low toxicity), long-term toxicity testing is not deemed necessary.

Based on the above information, Fatty acids C16-18, methyl esters (CAS No. 85586-21-6) can be expected to exert only low toxicity to sediment organisms.