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Fatty acids, C14-18 and C16-18-unsatd., zinc salts:

Aquatic toxicity data of Fatty acids, C14-18 and C16-18-unsatd., zinc salts are not available. Thus, read-across to structural analogue substances, i.e. zinc salts of fatty acids with equal or shorter alkyl chain length [fatty acids, C16-18, zinc salts, zinc dilaurate (C12)] is applied.

 

Freshwater, short-term toxicity:

Invertebrates: The acute toxicity of the structural analogue Fatty acids, C16-18, zinc salts to Daphnia magna was determined according to OECD 202 in M7 medium at pH 6 and 8 (Bouwman et al., 2003). The EC50 was not reached up to a loading rate of 100 mg fatty acids, C16-18, zinc salts/L. At this loading, the zinc concentration at the beginning of the test was 1170 μg Zn/L at pH 8 and 800 μg Zn/L at pH 6. The test report concludes: “No daphnids became immobilised during the test period... Although all daphnids exposed to the undiluted water fraction had test substance on their bodies at the end of the test, this did not hinder them”. Based on toxicity data of Fatty acids, C16-18, zinc salts, it is expected that the toxicity of the substance Fatty acids, C14-18 and C16-18-unsatd., zinc salts to daphnia is (far) above the water solubility limit of < 2 mg/L.The low potential for toxicity is further supported by the results of a screening study on a fatty acid zinc salt of similar chain length, i.e. zinc bis[12-hydroxyoctadecanoate], in which an EC50 was not reached at a nominal loading of 1000 mg/L (Rudolf 2002). Furthermore, the acute aquatic toxicity of zinc dilaurate (C12) to Daphnia magna is above the water solubility limit of ca. 5 mg/L; an EC50 was also not reached up to 10 mg zinc dilaurate/L at pH 7.8 (Muckle 2009). Thus, acute toxicity data of another structural analogue, i.e. zinc dilaurate - a zinc salt of a shorter-chained fatty acid (C12) with a relatively higher zinc content, support the conclusion that zinc salts of fatty acids are not acutely toxic to invertebrates.

 

Fish: Information on the structural analogue Fatty acids, C16-18, zinc salts on fish toxicity are available from a study performed according to EU Method C.1 (Acute Toxicity for Fish) in the former version of 1992 (Henkel KGaA, 1995), from a study performed according to OECD Guideline 203 (Fish, Acute Toxicity Test) but reported only in a short study report (TÜV Bayern Sachsen E.V. (1992)) and from an older publication (Dowden & Bennett, 1965). In the most reliable study (Henkel KGaA, 1995), fish (Danio rerio) were exposed for 96 hours to nominal concentrations of 0 (control), 1000, 3000 and 10000 mg/L under semi-static conditions. The nominal concentrations far exceed the water solubility of fatty acids, C16-18, zinc salts by 3 to 4 orders of magnitude. Measures to disperse the test substance in the test water were used. At all tested concentrations, including the highest nominal test concentration, neither behavioural abnormalities nor mortality occurred. In addition, no effects were observed at nominal fatty acids, C16-18, zinc salts concentrations up to the water solubility limit in two further studies. These findings are further supported by acute aquatic toxicity data of a similar zinc salt of shorter alkyl chain length (C12), i.e. zinc dilaurate (CAS No.: 2452-01-9), with a 96-h NOEC of 10 mg/L for fish that is above the respective water solubility limit of 5 mg/L (Muckle, 2009). In accordance with the evaluation of the EU Risk assessment on the structural analogue zinc distearate (Final report R074_0805_env, May 2008) and toxicity data on structural analogue substances, it is assumed that the acute toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts to fish is above the water solubility limit of < 2 mg/L.

Algae: The toxic effects of the dissolved fractions of the structural analogue Fatty acids, C16-18, zinc salts on the growth rate of algae (Pseudokirchneriella subcapitata) were studied in three tests according to OECD Guideline 201 (Wenzel, 2010a,b and 2013a). Whereas in the first test, the dissolved fraction of a loading of 100 mg/L in a non-standard test medium was diluted in series to allow the calculation of toxicity parameters (EL10, EL50) (Wenzel, 2010a), the dissolved fractions of several loadings (1, 10, and 100 mg/L) in non-standard test medium were tested in the second test according to OECD Series No. 23 (Wenzel, 2010b). In the third test by Wenzel (2013a), lower concentrations were applied (i.e. 0.01, 0.1, 1.0, 10 and 100 mg/L) in the standard test medium to enable the classification for a potential aquatic hazard based on respective loading of the applied dissolved fractions. The EL50 value for the 72-h inhibition of growth rate of P. subcapitata in the standard test medium is estimated with > 100 mg/L. Based on toxicity data of Fatty acids, C16-18, zinc salts, it is expected that the toxicity of the substance Fatty acids, C14-18 and C16-18-unsatd., zinc salts to algae is (far) above the water solubility limit of < 2 mg/L.

In addition, a growth inhibition test with P. subcapitata exposed to the dissolved fractions of the shorter-chained fatty acid (C12) zinc salt zinc dilaurate at loadings of 0.01, 0.1, 1 and 10 mg/L in standard test medium over a test period of 72 hours revealed calculated EL50 values for growth rate of 12.87 mg/L (extrapolated) while the EL10 was 3.73 mg/L, based on loadings of the applied dissolved fraction (Wenzel, 2013b). In growth inhibition tests of the alga Desmodesmus subspicatus performed with the structural analogue zinc bis[12-hydroxyoctadecanoate] and the shorter-chained zinc dilaurate (C12), 72h-EC50 as well as the 72h-NOEC values far above the maximum water solubility were observed (Rudolph 2002 and Muckle 2009, respectively). In sum, zinc salts of fatty acids with a similar structural analogy, water solubility and zinc content are not toxic to algae at concentrations ≤ relevant acute and chronic aquatic classification criteria; and the potential of Fatty acids, C14-18 and C16-18-unsatd., zinc salts for toxicity to freshwater algae and cyanobacteria is considered similarly low.

 

In sum, it is assumed that the acute toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts to fish, invertebrates and algae is above the water solubility limit of < 2 mg/L.

Freshwater, long-term toxicity:

Based on the comprehensive data set on aquatic long-term toxicity of zinc and mean values for standard species (i.e. Pseudokircherniella subcapitata, Daphnia magna, Oncorhynchus mykiss), algae appear to be the most sensitive taxa; respective NOEL/EL10 estimates for the long-term toxicity of zinc to invertebrates and fish are substantially higher (more than factor of 4) than the NOEL/EL10 value for algae. Thus, chronic toxicity data for algae determine the worst-case hazard and testing of further species is scientifically not justified. Chronic toxicity data of the structure analogue Fatty acids, C16-18, zinc salts are available for algae. The long-term toxic effects of dissolved fractions of this structural analogue on the growth rate of algae (Pseudokirchnerella subcapitata) were studied in a state-of-the-art test according to OECD Guideline 201 (Wenzel, 2013a). The dissolved fractions were prepared according to OECD Series No. 23 in the standard test medium to enable the classification for a potential chronic aquatic hazard based on dissolved fractions. Thus, dissolved fractions of the loadings 0.01, 0.1, 1.0, 10 and 100 mg/L were tested; the EL10 value for the 72-h inhibition of growth rate of P. subcapitata in standard test medium amounts to 3.31 mg/L.

Only limited long-term data are available for the aquatic toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts and its structural analogues. Thus, read-across to the assessment entities soluble zinc substances and C14-18 fatty acids is applied since zinc cations and fatty acid anions (C14-18) determine fate and toxicity in the environment. Since C14-18 fatty acids have a low potential for ecotoxicity, the freshwater hazard assessment of Fatty acids, C14-18 and C16-18-unsatd., zinc salts is based on zinc ions. Please refer to the endpoint summary of the respective assessment entity for further details.

Marine toxicity:

Marine toxicity data are not available for Fatty acids, C14-18 and C16-18-unsatd., zinc salts. Thus, read-across to the assessment entities soluble zinc substances and C14-18 fatty acids is applied since zinc cations and fatty acid anions (C14-18) determine fate and toxicity in the environment. Since C14 -18 fatty acids have a low potential for ecotoxicity, the marine hazard assessment of fatty acids, C14-18, zinc salt is based on zinc ions. Please refer to the endpoint summary of the respective assessment entity for further details.

 

Conclusions:

The toxicity of structural analogue fatty acids, C16-18, zinc salts to bacteria and the acute toxicity of these structural analogues to algae, daphnia and fish is above the water solubility limit of Fatty acids, C14-18 and C16-18-unsatd., zinc salts of < 2 mg/L. The chronic effect concentration of the most sensitive trophic level, i.e. the estimated EL10 value for the 72-h inhibition of algal growth rate by the structural analogue fatty acids, C16-18, zinc salts in a standard test amounts to 3.31 mg/L (based on testing the dissolved fractions of individual loadings). These conclusions are consistent with conclusions from the EU RAR for the structural analogue 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: "From these data, although very limited, it is concluded that the toxicity of zinc distearate to bacteria and the acute toxicity of zinc distearate to Daphnia magna and fish is (far) above the water solubility limit of around 1 mg/L)."

Even though aquatic toxicity data on structural analogues are available, a conservative read-across to the assessment entities soluble zinc substances and fatty acids is applied for the aquatic hazard assessment, since zinc cations and fatty acid anions determine fate and toxicity in the environment. Since C14-18-satd. and C16-18-unsatd. fatty acids have a low potential for ecotoxicity, the aquatic hazard assessment of Fatty acids, C14-18 and C16-18-unsatd., zinc salts is based on zinc ions.

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