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Toxicity to microorganisms

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Description of key information

ZINC DILAURATE:
The toxicity of zinc dilaurate to microorganisms is above the water solubility limit ranging from 5.2 to 6.4 mg/L.
However, as for all other environmental 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 also carried over to zinc dilaurate.
ZINC:
An activated sludge respiration test giving an EC50 (3d) of 5,2mg Zn/l (Dutka et al 1983).

Key value for chemical safety assessment

Additional information

ZINC DILAURATE:

Zinc dilaurate is produced by the oleochemistry sector, starting from natural fatty materials and consists of approximately 86% natural fatty acids and 14% zinc. Zinc dilaurate is a zinc salt of a medium-chained fatty acid containing 12 C-atoms. Thus, read-across of data available for zinc salts of shorter-chained (C8) and longer-chained (C16-18) fatty acids based on structural similarity, water solubility and zinc content and applying bridging principles in a conservative, worst-case approach is assumed to adequately describe the ecotoxic potential of zinc dilaurate (C12).Regarding the microbial toxicity of zinc salts of shorter-chained (C8) fatty acids, the substance octanoic acid, zinc salt, basic (CAS 90480-58-3) is readily biodegradable according to results of an OECD 301F- test (Simon, 2012); furthermore, inhibitory effects of octanoic acid, zinc salt, basic were not observed in the toxicity control (more than 25 % degradation within 14 days). According to ECHA Guidance on information requirements and CSA Chapter R.7b (November, 2102), „if a compound degrades well in a ready biodegradability test, or does not inhibit the degradation of a positive control at a certain concentration, this concentration can be used as a NOEC value.“ Thus, octanoic acid, zinc salt, basic (CAS 90480-58-3) is non-toxic at 100 mg/L.

Regarding zinc salts of longer-chained (C16-18) fatty acids, the toxicity of Fatty acids, C16-18, zinc salts to microorganisms is far above the water solubility limit (TÜV Bayern Sachsen .V., 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 (http://echa.europa.eu/documents/10162/08799aec-42c5-44e0-9969-baa022c66db1): "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 (the toxicity to microorganisms is far above the water solubility limit ranging from 5.2 to 6.4 mg/L) is considered for zinc dilaurate. 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]