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

Endpoint summary

Description of key information

Experimental data from streams in the category are not available. The category is considered inherently biodegradable based on ready biodegradability tests, peer-reviewd data obtained from the Concawe Report (2019) and QSAR data (BIOWIN, BioHCwin).

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.

In accordance to REACH Annex XI, Section 1.2 the surface water, sediment and soil biodegradation simulation studies are not required because the weight of evidence indicates that the constituents in the category would degrade rapidly in the environment and because their potential for adsorption to sediment and soil particles is considered to be low based on the log Koc criteria of 3.

The metabolites water, sediment and soil half-lives have been determined using the Kinetic 301F model in the OASIS/LMC Catalogic software (v5.11.19) and range from less than 1 day to 88 days and only three metabolites had half-lives of over one year. All the metabolies have log Kow values well below the B threshold and as such are not expected to be PBT or vPvB.

Additional information

The Persistence Weight of Evidence Evaluation and the PBT Evaluation follow different approaches to assess persistence. Please see both approaches for justification of the approach. Documents are found in Section 13.2.