Hydrocarbons, C7-8

Endpoint summary

Additional information

Phototransformation in air

 

Standard tests for atmospheric oxidation half-lives are intended for single substances and are not appropriate for this complex substance. 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 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. 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, this substance does not have the potential to undergo photolysis in water and soil, and this fate process will not contribute to a measurable degradative loss of this substance from the environment.

 

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. Hydrocarbons, C7-C8, cyclics, 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. Therefore, this degradative process will not contribute to their removal from the environment.

 

Biodegradation

 

A study using a standardized OECD 301F ready test guideline is available (Shell 1997) on hydrocarbons, C6-C7, n-alkanes, isoalkanes, cyclics, < 5% n-hexane for the purpose of read across. Results from this manometric respirometry test procedure demonstrated 98% biodegradation after 28 days. The data demonstrate that hydrocarbons, C7, n-alkanes, isoalkanes, cyclics can biodegrade readily and to high extents. Therefore no further testing is conducted on biodegradation in water and sediment as well as on biodegradation in soil.

 

Bioaccumulation

 

As regards bioaccumulation, the substance is a hydrocarbon UVCB and standard tests on bioaccumulation are intended for single substances and are not appropriate for this complex substance. However, as regards aquatic bioaccumulation 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. With regard to terrestrial bioaccumulation, this endpoint has been calculated for representative hydrocarbon structures using default algorithms in the EUSES model as input to the hydrocarbon block method incorporated into the PETRORISK model. In both cases 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.

 

Adsorption / desorption

 

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 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).

 

Distribution modelling

 

The distribution of the substance in the environmental compartments, air, water, soil, and sediment, has been calculated using the PETRORISK Model, version 5.0. 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.