Reaction mass of ethanol and propan-2-ol

Sediment toxicity

Description of key information

FROM ETOH
LC50 (18hr, Hyallela sp.) = 8200mg/l
LC50 (18hr, Palaemonetes sp.) = 10100mg/l
LC50 (18hr, Lumbriculus sp) >100mg/l (limit test)

Additional information

There are no data available for the reaction mass. Data on one of the constituents (ethanol) shows low toxicity towards sediment organisms. Further testing on sediment organisms is not warranted for the reaction mass as the substance is readily biodegradable and has a low adsorption potential. The sediment compartment is not the main target compartment when the reaction mass will be released to the environment.

Ethanol:

A study for sediment toxicity is not required as the substance is readily biodegradable and therefore exposure of sediment is unlikely. Indeed fugacity calcuations predict that sediment concentrations are likely to be less than 0.1% of those found in water. 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 was seen once toxicity was observed. Level 3 fugacity modelling with a realistic split of mass flow inputs per compartment indicate that sediment concentrations would significantly lower than those of water (~30%) which would permit the extrapolation of toxicity data from the aquatic compartment to reasonably predict toxicity in sediment. In reality, concentrations would be less in sediment as the substance is readily biodegradable. In a similar, sediment free screening limit test, Lumbriculus variegatus showed no mortality at a concentration of 100mg/l. The values from these studies cannot be used to derive a PNEC in terms of mg/kg sediment since sediment was not used in the study. On the basis that the substance is readility biodegradable and good aquatic toxicity information is available, no further testing for sedimentary organism toxicity is therefore required.