Hydrocarbons, C12-C18, isoalkanes, cyclics, 2-30% aromatics

Endpoint summary

Description of key information

Hydrolysis

Hydrolysis is a reaction in which a water molecule or hydroxide ion substitutes for another atom or group of atoms present in a chemical resulting in a structural change of that chemical. Potentially hydrolyzable groups include alkyl halides, amides, carbamates, carboxylic acid esters and lactones, epoxides, phosphate esters, and sulfonic acid esters (Neely, 1985). The lack of a suitable leaving group renders compounds resistant to hydrolysis.

 

The chemical constituents that comprise this substance consist entirely of carbon and hydrogen and do not contain hydrolysable groups. As such, they have a very low potential to hydrolyze. Therefore, this degradative process will not contribute to their removal 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 Section 13 of the dossier).

 

The phototransformation rate for representative constituents of this substance is in the range 4.50 x 10^-12 and 1.19 x 10 ^-10 cm3/molecule/sec. The half-lives of representative constituents of this substance were in the range 0.09 and 2.38 d.

 

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. This substance contains hydrocarbon molecules that absorb UV light below 290 nm, a range of UV light that does not reach the earth's surface. Therefore, these substances 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 

There is no data available for Hydrocarbons, C12-C18, isoalkanes, cyclics, 2-30% aromatics. However, key data is available for structural analogues, Hydrocarbons, C14-C18, n-alkanes, isoalkanes, cyclics, aromatics (2-30%) and presented in the dossier. This data is read across to Hydrocarbons, C12-C18, isoalkanes, cyclics, 2-30% aromatics based on analogue read across and a discussion and report on the read across strategy is provided as an attachment in IUCLID Section 13.

 

Data read-across from the source substance showed that it biodegraded to an extent of 61% after 28 days in an OECD 301F study. The data support characterizing the source substance substance (Hydrocarbons, C14 -C18, n-alkanes, isoalkanes, cyclics, aromatics (2-30%)) as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10 -day window requirement, it is characterized as readily biodegradable because the criteria is not applied to multi-component substances when assessing their ready biodegradability.

 

This substance is therefore also expected to be readily biodegradable.

 

Biodegradation in water: simulation tests 

This substance is readily biodegradable. Therefore, simulation tests in water are not required.

 

 Biodegradation in sediment: simulation tests 

This substance is readily biodegradable. Therefore, simulation tests in sediment are not required. 

 

Biodegradation in soil

This substance is readily biodegradable. Therefore, simulation tests in soil are not required.

 

Bioaccumulation: aquatic/sediment

The substance is a hydrocarbon UVCB. Standard bioaccumulation studies for this endpoint are intended for monoconstituent substances and are not applicable for this complex substance. However, this endpoint is characterised using 2 separate 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 in IUCLID section 13).

 

The bioconcentration factor (BCF) was calculated using the Arnot-Gobas upper trophic model and normalised to a 5% lipid concentration. The calculated BCF for constituents potentially present in this substance ranged from 2.81 to 2626 L/kg (OECD, 2021).

 

The bioconcentration factor (BCF) was calculated using the log Kow regression model. The calculated BCF for constituents potentially present in this substance ranged from 39.81 to 19055 L/kg (OECD, 2021).

 

Bioaccumulation: terrestrial 

This substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. 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 

The substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint is characterised 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 report attached in IUCLID section 13).

 

Log Koc has been calculated using Petrorisk. The Log Koc for this substance ranges from 2.55 to 8.55 (CONCAWE, 2021).

 

Henry’s law constant:

Volatilisation is dependent on Henry's Constant (HC) which is not applicable to complex substances.

The substance is a hydrocarbon UVCB. Standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, this endpoint is characterised 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 report attached in IUCLID section 13).

Henry's Law Constant has been calculated using Petrorisk. The Henry's Law Constant for this substance ranges from -451910 to 175292 Pa.m^3/mol (CONCAWE, 2021).