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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The estimated freshwater algae 72-h EL50 (Effective Loading Rate) value is 4.34 mg/L based on biomass.
The estimated freshwater algae 72-h NOELR (No Observed Effective Loading Rate) value is 0.97 mg/L based on biomass.

Key value for chemical safety assessment

Additional information

There are measured toxicity data available for heptane on a mixture of ocean phytoplankton (Brooks et al. 1977). However, the test procedure was flawed and the reported data do not reliably characterize the aquatic toxicity of the test substance. Thus, an EL50 (72 h) and a NOELR (72 h) were calculated.

The aquatic toxicity was estimated 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 partitioning coefficients (KMW) that describe the partitioning of the hydrocarbons between the water and organism. The estimated freshwater algae 72-h EL50 (Effect Loading Rate) and NOELR (No Observed Effect Loading Rate) values are 4.338 and 0.97 mg/L, respectively, based on biomass.