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Toxicity to soil microorganisms

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FATTY ACIDS, C14-18 AND C16-18-UNSATD., ZINC SALTS: 
As toxicity data are not available for Fatty acids, C14-C18 and C16-18-unsatd., zinc salts, read-across to insoluble/ slightly soluble zinc substances is made.
ZINC:
For microbial assays, in total 108 individual high quality NOEC/EC10s represent 4 nitrogen transformation processes, 5 carbon transformation processes and 8 enzymatic processes and range from 17 mg Zn/kg dw for respiration to 2623 mg Zn/kg dw for phosphatase.

Key value for chemical safety assessment

Additional information

FATTY ACIDS, C14-18 AND C16-18-UNSATD., ZINC SALTS:

As terrestrial toxicity data are not available for Fatty acids, C14-C18 and C16-18-unsatd., zinc salts, read-across to insoluble/ slightly soluble zinc substances is made. It is assumed that upon dissolution Fatty acids, C14-18 and C16-18-unsatd., zinc salts is changed in part to ionic zinc and that only ionic zinc is determining biological activities. The ecotoxic potential of the fatty acid chain is assumed to be negligible. Fatty acids are generally not considered to represent a risk to the environment, which is reflected in their exclusion from REACH registration requirements (c.f. REACH Annex V (Regulation (EC) No 987/2008)).For a comprehensive overview of the toxicity of zinc, see the hazard assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 in Appendix 1 of the CSR and cited in excerpts below.

ZINC:

For microbial assays, in total 108 individual high quality NOEC/EC10s are selected for the PNEC derivation. These values represent 4 nitrogen transformation processes, 5 carbon transformation processes and 8 enzymatic processes and range from 17 mg Zn/kg dw for respiration (Chang and Broadbent, 1981 and Lighthart et al., 1983) to 2623 mg Zn/kg dw for phosphatase (Doelman and Haanstra, 1989).

Information on the background Zn concentration, allowing correction for differences in bioavailability among soils, is only available for 76 NOEC or EC10 values, representing 13 microbial processes (4 for N cycle, 5 for C cycle and 4 enzymatic processes). The total range in NOEC/EC10 values for the dataset with results for background Zn concentration is the same as for the total dataset for micro-organisms.

All toxicity data are expressed as added Zn concentration in soil, based on either the nominal dose added or on measured, background corrected soil Zn concentrations.