Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Isoheptane has the potential to volatilize to air, based on a relatively high vapor pressure, where it is subject to atmospheric oxidation. In air, octane can react with photosensitized oxygen in the form of hydroxyl radicals (OH-).

Estimation with the APOWIN model (HSPA Consortium 2009) resulted in a test substance half-life, as mediated by hydroxyl radical (OH-) attack is calculated as1.56 days based on a 12-hour day (the 12-hour day half-life value normalizes degradation to a standard day light period during which hydroxyl radicals needed for degradation are generated). The half-life was calculated based on an OH- reaction rate constant of 6.8630 E-12 cm3/molecule-sec and an OH- concentration of 1.5E6 OH/cm3.

Isoheptane as well as other constituent chemicals of the C7-C9 aliphatic hydrocarbon solvents category are composed of carbon and hydrogen and are not amenable to hydrolysis because of their molecular structure and the chemical reaction required for this type of transformation to occur.

No data are available on the biodegradation of isoheptane. Based on a category approach data are read-across to hydrocarbons, C7-C9, isoalkanes. The data show that isoheptane is not readily biodegradable, but can demonstrate high extents of biodegradability when test durations are extended. Thus, isoheptane is not expected to persist in the environment under aerobic conditions.

Data on bioaccumulation are estimated. BCF values for the category members are in the range of 11.81 to 1216 (log BCF of 1.07 to 3.08), including Isoheptane with a BCF and Log BCF of 129 and 2.11, respectively.

Category members are not expected to sorb significantly to organic matter in soil, sediment, and wastewater solids based on calculated log Koc values, with Isoheptane having a log Koc of 2.30.

The distribution of the substance in the environmental compartments, air, water, soil, and sediment, has been calculated using the PETRORISK Model, version 5.2. Based on the regional scale exposure assessment, the multimedia distribution of the substance is 96% to air, 1.6% to water, 0.65% to soil and 2.1% to sediment. Distribution modeling results are included in the 'Multimedia distribution modeling results' tab in the PETRORISK spreadsheet attached to IUCLID Section 13.