Tar acids, xylenol fraction

Toxicity to soil microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to soil microorganisms

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

Waiving according to outcome of risk assessment and the Integrated Testing Strategy for toxicity to sediment (ECHA, 2017; Endpoint specific guidance, Chapter R.7c, Section 7.11.6).

Additional information

In accordance with Regulation (EC) No 1907/2006, Column 2 of Annex IX, section 9.4, toxicity tests on soil organisms do not need to be conducted if the outcome of the chemical safety assessment shows no indication of risk on soil organisms from exposure to the substance in question. The PNEC soil is derived to be 0.096 mg/kg dw from a test with terrestrial plants using an assessment factor of 1000, since no further data on other trophic levels are available. Additionally a PNEC soil was derived using the equilibrium partitioning method on the basis of available data for xylenol-isomers as they are the main constituents of Tar acids, Xylenol fraction (CAS 84989-06-0). This PNEC soil based on EPM resulted in 0.3093 mg/kg dw. Since the latter calculated value is less sensitive than the one based on measured data, derivation of the RCRs is based on the PNEC soil of 0.096 mg/kg soil dw. The risk assessment performed showed no indications of risks as all RCRs are below 1. Taking all the available information mentioned above into account no further testing with terrestrial organisms is required.

Although only data on plants are available the above approach is further corroborated by the “Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance”, Section 7.11.6, Integrated testing strategy (ITS) for Effects on Terrestrial Organisms (ECHA, 2017). This guidance provides information how to address risk assessment in case no data on soil organisms at all would be available. According to this guidance existing information on aquatic toxicity data (PNEC aqua) and adsorption potential in soil shall be considered to assign substance to a “soil hazard category” and to perform a screening assessment. Aquatic toxicity data are available for all trophic levels and a PNEC freshwater is derived to be 0.1 mg/L. The risk assessment performed showed no indications of risks as all RCRs are below 1. Further there is no indication for high adsorption of the substance in soil. All available data for the main components of Tar acids, xylenol fraction (CAS 84989-06-0) demonstrate the log Kow to be below 3, i.e. xylenol-isomers: 2.09 to 2.42 (DEZA, 2010; EPA, 2010; Sangster, 1989); cresol-isomers: 1.94 to 1.98 (OECD SIDS, 2003; Sangster, 1989); ethyl-phenols: 2.09 to 2.58 (DEZA, 2010; Umeyama et al., 1971; Sangster, 1989), or trimethyl-phenols: 2.67 to 2.73 (Sangster, 1989). Thus, Tar acids, xylenol fraction (CAS 84989-06-0) exhibits low potential for adsorption to soil (trigger log Kow < 5). Following the ITS also resuts in no need for further testing with terrestrial organisms.