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FATTY ACIDS, C14 -18 AND C16 -18 -UNSATD., ZINC SALTS: 
Based on similar structural analogy, water solubility and zinc content of Fatty acids, C14-18 and C16-18-unsatd., zinc salts (CAS 67701-12-6) and Fatty acids, C16-18, zinc salts (CAS 91051-01-3), a 1:1 read-across of ecotoxicological data of Fatty acids, C16-18, zinc salts is applied to Fatty acids, C14-18 and C16-18-unsatd., zinc salts.
The toxicity of Fatty acids, C16-18, zinc salts to bacteria is far above the water solubility limit of around 1 mg/L. Thus, as the structural analogue is nontoxic to aquatic micro-organisms up to and including its water solubility, a similar lack of toxicity is assumed for Fatty acids, C14-18 and C16-18-unsatd., zinc salt. Thus, Fatty acids, C14-18 and C16-18-unsatd., zinc salts does also not pose a hazard to aquatic micro-organisms.
However, as for all other PNECs, a read-across to insoluble/slightly soluble zinc substances is made, the PNEC sewage treatment plant as derived in the Chemical Safety Assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 (see Appendix 1 of the CSR) is read-across to Fatty acids, C14-18 and C16-18-unsatd., zinc salts.
ZINC:
An activated sludge respiration test is giving an EC50 (3d) of 5,2mg Zn/l (Dutka et al 1983).

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

Based on similar structural analogy, water solubility and zinc content of Fatty acids, C14-18 and C16-18-unsatd., zinc salts (CAS 67701-12-6) and Fatty acids, C16-18, zinc salts (CAS 91051-01-3), a 1:1 read-across of ecotoxicological data of Fatty acids, C16-18, zinc salts is applied to Fatty acids, C14-18 and C16-18-unsatd., zinc salts.

The toxicity of Fatty acids, C16-18, zinc salts to microorganisms is far above the water solubility limit (TÜV, 1992; Berger, 1995). Similar conclusions from were drawn in the EU RAR Zinc distearate (CAS-No.: 557-05-1 & 91051-01-3 EINECS-No.: 209-151-9 & 293-049-4) Part 1 - Environment (Final report R074_0805_env, May 2008: "The two available tests with bacteria resulted in NOEC values of 1000 mg zinc distearate/L (Berger, 1995b:Pseudomonas putida) and 1560 mg zinc distearate/L (TÜV, 1992: Microtoxtest according to DIN 38412, part 34). In the latter study an EC20 of 6250 mg zinc distearate /L was calculated, with the remark that an EC50 could not be derived because of the low effect response. These nominal concentrations are at least 3 orders of magnitude higher than the water solubility limit for zinc distearate (around 1 mg/L)."

A similar lack of toxicity to microorganisms (toxicity to microorganisms is far above the water solubility) is considered for Fatty acids, C14-18 and C16-18-unsatd., zinc salts. For a comprehensive overview of the toxicity of zinc to microorganisms, 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:

Several data available for this endpoint. The EC50 reported from the study by Dutka et al (1983), is giving the lowest reliable value. This study was also used in the EU risk assessment to assess the PNEC for STP.

[Dutka BJ, Nyholm N and Petersen J. (1983). Comparison of several microbiological toxicity screening tests.Water research volume 17, nr10, 1363-1368]