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Sediment toxicity

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Description of key information

LC50 (18hr, Hyallela sp.) = 8,200mg/l
LC50 (18hr, Palaemonetes sp.) = 10,100mg/l
LC50 (18hr, Lumbriculus sp) >100mg/l (limit test)

LC50 (48hr, C Elegans) = 36,900mg/L

EC50 (reprotoxicity, 96hr, C Elegans) ~ 6,300mg/L

Key value for chemical safety assessment

Additional information

A study for sediment toxicity is not required as the substance is readily biodegradable and the logKow is very low, therefore exposure of sediment is unlikely. The low toxicity of the substance to aquatic species means that the equilibrium partitioning method can be applied with confidence to assess the hazard to sediment dwelling organisms.

There is some however, some data on the toxicity of ethanol to sediment dwelling organisms from acute toxicity data screening studies.

In a reliable 18 hour acute toxicity study which looked at the toxicity of sediment dwelling organisms using a screening assay more typical of those used for water dwelling species (ie no sediment present), Hyalella azteca (scuds) and Palaemonetes kadiakensis (glass shrimp) were exposed to ethanol at aqueous concentrations in the range 0.8 to 2.5% (v/v). LC50's of 1.04% and 1.28% (v/v) respectively were obtained (equivalent to 8200 and 10100mg/l) based on an end point of mortality (measured as immobility). The results with the glass shrimp showed a very steep dose response curve once toxicity was observed. In a similar, sediment free screening limit test, Lumbriculus variegatus showed no mortality at a concentration of 100mg/l. In a study designed to generate data to prepare a QSAR model, the acute (48hr) and chronic (96hr) toxicity of ethanol to the soil/sediment dwelling species C. Elegans was assessed. Acute toxicity was measured in terms of mobility as a proxy for lethality with a derived LC50 values of 36900mg/L. Chronic toxicity was measured in terms of impact on reproduction and growth rate with EC50 values of 6660mg/L and 6200mg/L respectively for these two end points. The differences in the findings for the two end points was within statistical variation so they can be considered effectively the same.

The values from these studies cannot be used directly to derive a PNEC in terms of mg/kg sediment since sediment was not used. However, using the partitioning method and a partition coefficient of -0.32 plus the lowest LC50 value of 8,200mg/L would lead to a sediment LC50 of 30,500mg/kgdw and based on the chronic data from C Elegans, an EC50 of 23,100mg/kgbw