Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

No ecological toxicity data is available for 2,2,3-trimethylbutane. However, data is available for isoheptane; hydrocarbons, C7-C9, isoalkanes; and hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics. This data is being read across from using the category approach explained in the category justification document attached to Section 13 of the dossier. Additionally, based on an analogue approach, data are also being read-across from another isoalkane substance, i.e. 2,2,4-trimethylpentane.


A study with hydrocarbons, C7-C9, isoalkanes was conducted according to OECD 203 (CEFIC, 1995). The acute toxicity, as measured by mortality to rainbow trout (Oncorhynchus mykiss), was evaluated in freshwater by using water accommodated fractions (WAFs). Under the conditions of this study, the test substance, hydrocarbons, C7-C9, isoalkanes produced acute lethal toxicity to Oncorhynchus mykiss at 18.4 mg/L, based on nominal loadings of the test substance in water.


The long-term toxicity of Isoheptane to fish was calculated 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 fish 28 -day NOELR value for Isoheptane is 2.426 mg/L.


Data on the acute toxicity on freshwater and marine aquatic invertebrate species are read-across to 2,3,4-trimethylpentane (Adema & van den Bos Bakker, 1986). The acute toxicity, as measured by immobilisation of Daphnia and mortality to Chaetogammarus and Mysidopsis, was evaluated in fresh- and saltwater by using water accommodated fractions (WAFs). 2,3,4-trimethylpentane produced acute toxicity to Daphnia and Mysidopsis at 2.4 mg/L, and to Chaetogammarus at 5.4 mg/L based on nominal loadings of the test substance in water.


Data on the chronic toxicity are read-across to hydrocarbons, C7-C9, n-alkanes, isoalkanes, cyclics based on a category approach. A study of the chronic toxicity, as measured by survival, sublethal effects, reproduction, and length of first generation adults, conducted with Daphnia using WAFs (Wilbury Laboratories 2004) resulted in a NOELR of 1 mg/L.


Toxicity of Isoheptane to algae and microorganisms was estimated using the Petrotox computer model (v. 3.04). The estimated freshwater algae 72-h EL50(Effect Loading Rate) and NOELR (No Observed Effect Loading Rate) values are 8.204 and 1.835 mg/L, respectively, based on biomass. The estimated protozoan,Tetrahymena pyriformis, 48-hr EL50value for Isoheptane is 42.756 mg/L, based on growth inhibition.

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