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Environmental fate & pathways

Endpoint summary

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Description of key information

Hydrolysis:

Further testing is not required. Based on the data presented in this dossier, substances in the category Hydrocarbons, C14 -C20, aliphatics, 2% aromatics have been shown to be readily biodegradable. According to column 2 of Annex VII on the standard information requirements, hydrolysis studies do not need to be conducted if the substance is readily biodegradable. Moreover, hydrolysis is not expected to be a signifcant mechanism of degradation in the environment because the substances within the category lack hydrolitically reactive functionnal groups. Therefore, it is not subject to hydrolysis and this process will not contribute to the degradative loss from the environment.

Phototransformation in air:

Standard tests for atmospheric oxidation half-lives are intended for single substances and are not appropriate for these complex substances. However, this endpoint is characterized using quantitative structure property relationships for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of these substances with the PETRORISK model (see library tab in PETRORISK spreadsheet attached to IUCLID section 13).

Phototransformation in water and soil:

The direct photolysis of an organic molecule occurs when it absorbs sufficient light energy to result in a structural transformation. The absorption of light in the ultra violet (UV) -visible range, 110-750 nm, can result in the electronic excitation of an organic molecule. The stratospheric ozone layer prevents UV light of less than 290 nm from reaching the earth's surface. Therefore, only light at wavelengths between 290 and 750 nm can result in photochemical transformations in the environment.

 

A conservative approach to estimating a photochemical degradation rate is to assume that degradation will occur in proportion to the amount of light wavelengths >290 nm absorbed by the molecule. Hydrocarbons, C14-C20, aliphatics, ≤2% aromatics contain hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, Hydrocarbons, C14-C20, aliphatics, ≤2% aromatics do not have the potential to undergo photolysis in water and soil, and this fate process will not contribute to a measurable degradative loss of these substances from the environment.

Biodegradation:

Based on the biodegradation results from relevant substances within the category, Hydrocarbons, C14-C20, aliphatics (≤2% aromatics) were found to be readily biodegradable (biodegradation > 60% ThOD) in OECD 306 ready biodegradability tests. Taking into account that all those substances have been found biodegradable in the seawater 306 test, lead to the conclusion that all the substances belonging to this category have the same properties and are therefore considered readily biodegradable.

Bioaccumulation:

C14-20 Aliphatics (≤2% aromatic) are hydrocarbon UVCBs. Standard tests for this endpoint are intended for single substances and are not appropriate for these complex substances. However, this endpoint has been calculated for representative hydrocarbon structures using the BCFWIN v2.16 model within EPISuite 3.12 as input to the hydrocarbon block method incorporated into the PETRORISK model. The predicted BCFs for hydrocarbons are generally overly conservative since biotransformation is not quantitatively taken into account. Therefore, indirect exposure and resulting risk estimates predicted by PETRORISK are likely to be overestimated. For the purposes of PBT assessment, measured bioaccumulation data for representative hydrocarbon constituents have been used as detailed in section 8 of the CSR.

Adsorption / desorption:

C14-20 Aliphatics (≤2% aromatic) are hydrocarbon UVCBs. Standard tests for this endpoint are intended for single substances and are not appropriate for these complex substances. However, this endpoint is characterized using quantitative structure property relationships for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of this substance with the PETRORISK model (see Product Library in PETRORISK spreadsheet attached to IUCLID Section 13).

 

Henry's Law Constant (Volatility):

Volatilisation is dependent on Henry's Constant (HC) which is not applicable to complex substances. Standard tests for atmospheric oxidation half-lives are intended for single substances and are not appropriate for these complex substances. However, this endpoint is characterized using quantitative structure property relationships for representative hydrocarbon structures that comprise the hydrocarbon blocks used to assess the environmental risk of these substances with the PETRORISK model (see library tab in PETRORISK spreadsheet attached to IUCLID section 13).

 

Distribution modelling:

The distribution of C14-20 Aliphatics (≤2% aromatic) in the environmental compartments, air, water, soil, and sediment, has been calculated using the PETRORISK Model, version 5.2. Computer modeling is an accepted method for estimating the environmental distribution of chemicals. Distribution modeling results are included in the 'Multimedia distribution modeling results' tab in the PETRORISK spreadsheet attached to IUCLID section 13.

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