Hydrocarbons, C3-6, C5-rich, steam-cracked naphtha

Endpoint summary

Description of key information

There are no experimental data available to assess the environmental fate and pathways of streams of this category. The different endpoint values have been predicted using QSAR data for measured constituents of this category (at equal or above 0.1% w/w).

The indirect OH photolysis half-life was predicted using AOPWIN and ranged between 0.056 and 5.88 days, considering 12-h daylight. The peer-reviewed data, BIOHCwin, BIOWIN and Catalogic Kinetic 301F models predict that the majority of the constituents are expected to be not persistent. The predicted BCF values range from 6.9 to 552 L/kg ww, so no constituent has a BCF value of greater than 2000 L/kg ww. The predicted log Koc of measured constituents of these streams using KOCWIN and the MCI method range from 1.5 to 2.65. Most of the parent constituents have a log Koc of < 3, which indicates that they will not preferentially adsorb to sediment or soil particles and are therefore not considered to be persistent in sediments or soils. No constituent or metabolite is considered to be PBT/vPvB.

It is not technically feasible to perform simulation testing on ultimate degradation in sediment, surface water or soil on UVCBs. Current test procedures are not suitable for the characterisation of the degradation potential and potential metabolite formation of these substances due to their complex compositions. For this reason, the persistence assessment for this category was conducted by evaluating the individual constituents reported by the registrants (co- and lead) at a concentration of = 0.1% (w/w). The degradation potential in surface water indicated that the constituents would not be persistent if released to water. The category constituents’ degradation evaluation indicated that when physico-chemical properties (e.g., volatilization), abiotic and biotic processes are addressed collectively none of the constituents would persist in surface water. Therefore, simulation testing on ultimate degradation in surface water does not appear to be scientifically necessary. The adsorption/desorption potential evaluated for the category constituents using the log Koc screening criterion value of 3 indicates that the constituents do not have significant adsorption potential. Therefore, sediment and soil biodegradation simulation tests do not appear to be scientifically necessary as the category constituents degrade rapidly in the environment and there is very low potential for them to adsorb to sediment and soil particles.

It is also not feasible to perform adsorption/desorption tests in UVCB streams. For this reason, these endpoints have been adapted by using QSAR predictions.

Additional information

According to REACH Annex VIII, a hydrolysis study does not need to be conducted if the substance is readily biodegradable, or the substance is highly insoluble in water. However, evaluation of the molecular structure of the constituents indicates that this endpoint is scientifically not necessary for this category as none of the constituents contain any hydrolysable groups such as hydroxyl, sulfhydryl, carbonyl, carboxyl, amino, or phosphate groups. Therefore, conducting this type of study would not yield any useful information about the possible decomposition of constituents in the environment. Therefore, according to REACH Annex XI Section 1.2, the study can be waived because testing does not appear to be scientifically necessary based on the structures of the constituents.