Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

This substance is a complex mixture of hydrocarbons with different fate and physical chemical properties. Therefore, most critical properties such as water solubility, octanol-water partition coefficient, adsorption coefficient and bioaccumulation are not technically feasible to determine for the substance.

The hydrolysis is not relevant fate process for this substance because it lacks functional groups associated with hydrolysis. The biodegradation in water and soil is the most important fate process of this substance. A good quality screening test OECD 301F was perfomed in accordance with GLP (American Petroleum Institute, 2008) on a read-across substance (High naphtenic, heavy, straight-run naphtha). The study result showed that the substance is readily biodegradable. Two screening tests (OECD 301F, GLP) conducted on the target UVCB substance produced unexpectedly low biodegradation results (0 and 8 % biodegradation). Due to a obvious problems with sampling and sample handling highly volatile components might have evaporated prior testing. Thus these studies were considered not reliable and are indicated as supporting studies only. In addition, to further support the conclusion that the target UVCB substance is readily biodegradable is derived from the EPISUITE tool. The estimation of the biodegradation for the ten most abundant individual structures in the target UVCB substance showed that it contains both biodegradable and non-biodegradable hydrocarbons.

The biodegradation in soil is affected with several parameters such as composition of the substance, aging and weathering of the substance, and soil characteristics (e.g. pH, nutrients, carbon content, soil texture). Testing of freshly prepared samples with simulation tests were considered technically unfeasible. However, based on the literature there are studies presenting the biodegradation potential of fossil fuels in soils with similar chemical composition as this substance. The natural attenuation is also one remediation method for oil contaminated soils. However, the main fate process of this substance is evaporation to atmosphere.

Based on the water solubility study this substance is only slightly soluble in water (18 mg/l at 25 deg. C.). The log Kow determined for the substance (log Kow 4.7) indicates the adsorption potential and bioaccumulation of the substance. Based on the vapour pressure (29.8 kPa at 37.8 deg. C) the evaporation to atmosphere is expected. The model used for exposure assessment and risk characterisation assumes that most of the substance is distributed to air as presented below.

As part of the environmental exposure assessment, the environmental fate properties of the substance were estimated with the PETRORISK tool. The estimated values were used in the quantitative risk assessment with the tool. The estimation is based on representative individual structures and their properties as included in the model database.

The following properties were used to describe the fate of the substance for CSA in the environmental ES&RC (CSR 9&10):

Half-life in air:

The estimated half-life values in air with the PETRORISK tool (CONCAWE Library) ranged from 1.5 h to 66 h.

Biodegradation:

Biodegradation potential was estimated with the BIOWIN v4.10 model, which is part of the EPISUITE tool. The probability of biodegradation was estimated for the ten most abundant individual structures (based on mass-%) of the substance according to the available analytical information.

BIOWIN estimates the probability biodegradation of an organic compound in the presence of mixed populations of environmental microorganisms. Of the ten most abundant individual structures, nine were estimated to be readily biodegradable, and the time required for ultimate degradation for these components were estimated to be days to weeks, or weeks.

Bioaccumulation:

Bioconcentration factors and bioaccumulation factors were estimated with the BCFBAF v3.01 model. The estimated log BCF value for the for the ten most abundant individual structures of the substance ranged from 2.02 to 3.08. The estimated log BAF value for the for the ten most abundant individual structures of the substance ranged from 2.03 to 3.88.

Transport and distribution:

Environmental fate information related to transport and distribution was estimated with the PETRORISK tool. The log Koc values and Henry's Law constant (HLC) values were estimated based on the database included in the model. In addition, distribution to different environmental compartments was modelled with the tool.

The estimation of log Koc values and HLC values is based on individual compound structures, which are included in the CONCAWE Library. The overall range (all components) for the estimated log Koc values was from 1.83 to 5.20. The log Koc values of the representative individual structures that form the major part of the substance based on mass fraction (sum 0.7) are in the range 2.70 - 4.30.

The overall range for the estimated Henry's Law constant (HLC) values was from 0.00036 atm m³/mol to 8.416 atm m³/mol. The HLC values of the representative individual structures that form the major part of the substance based on mass fraction (sum 0.7) were in the range 0.521 atm m³/mol - 3.823 atm m³/mol.

According to the PETRORISK modelling results, major part of the emissions of the substance are distributed to air (ca. 97.6 %). Fractions distributed to other environmental compartments is expected to be low; water (1.7 %), sediment (0.45 %), soil (0.25 %)