Hydrocarbons, C5-C7, n-alkanes, isoalkanes, < 5% n-hexane

Short-term toxicity to aquatic invertebrates

Description of key information

EC50 (48h) = 2.7 mg/L (measured, Daphnia magna, read-accross from pentane)

Additional information

There are no data available on the acute toxicity to invertebrates of hydrocarbons, C5-C6, n-alkanes, isoalkanes, <5% n-hexane. However, there are reliable data available considered suitable for read-across using the analogue approach.

The target substance is a hydrocarbon solvent with carbon numbers in the range of C5 to C6. The main constituents of the mixed solvent consist of about 43% of C6 species and about 57% of C5 species. n-Hexane is only present in concentrations < 5% of the total volume.

Taking into account all available data, animal and human toxicity data as well as environmental fate and effects data show that source substances have a similar (eco-)toxicological and environmental fate properties as the target substance.

Therefore, read-across is performed based on an analogue approach (for details please refer to the analogue justification which is attached in section 13 of the technical dossier).

For a number of analogue substances the aquatic toxicity was estimated by a QSAR, using the Petrotox computer model (v 3.04), which combines a partitioning model used to calculate the aqueous concentration of hydrocarbon components as a function of substance loading with the Target Lipid Model used to calculate acute and chronic toxicity of non-polar narcotic chemicals. Petrotox computes toxicity based on the summation of the aqueous-phase concentrations of hydrocarbon block(s) that represent a hydrocarbon substance and membrane-water partition coefficients K(MW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated freshwater 48 hour EL50 values based on immobility are as follows:

Hydrocarbons, C6, isoalkanes, < 5% n-hexane: 31.9 mg/L (Concawe 2009)

Hexane: 21.85 mg/L (Concawe 2009)

Hydrocarbons, C5-C7, n-alkanes, isoalkanes, n-hexane rich: 23.22 mg/L (Concawe 2009)

Hydrocarbons, C6, n-alkanes, isoalkanes, cyclics, n-hexane rich: 23.35 mg/L (Concawe 2009)

Pentane: 48.11 mg/L (Concawe 2009)

A further QSAR for pentane is available by Bol et al. (1993), reporting an EC50(48h) of 2.8 mg/L.

Experimental data are also available for hexane and pentane. In a study with Daphnia magna exposed to hexane under static conditions an nominal LC50 of 3.9 mg/L was determined (Bobra et al., 1983). The study with pentane was also conducted under static conditions by Adema & van den Bos Bakker (1987). These authors report EC50 values of 2.7 mg/L (measured) and 9.1 mg/L (nominal).

Although both of the latter studies are non-GLP non-guideline studies, the study by Adema & van den Bos Bakker (1987) was chosen as key study, since the study resulted in the most critical value with 2.7 mg/L and thus reflects a worst case.