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

Short-term toxicity to fish

Description of key information

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

Data are not available for the toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts to fish. 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; C12 zinc dilaurate) is applied.

The acute toxicity of the structural analogue fatty acids, C16-18, zinc salts to fish is above its water solubility limit of around 1 mg/L. Based on toxicity data of the structural analogue, it is expected that the toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts is above the water solubility limit as the substance is less soluble (water solubility of Fatty acids, C14-18 and C16-18-unsatd. = < 2 mg/L). A similar conclusion was made on a structural analogue (i.e. similar fatty acid zinc salt) 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) as follows: "In the three available acute toxicity tests with fish (TÜV, 1992: fish species not reported; Berger, 1995a, b: zebrafish Brachydanio rerio; Dowden & Bennett, 1965: bluegill Lepomis macrochirus), no effects were observed at nominal zinc distearate concentrations up to the water solubility limit or at nominal concentrations that were 3 to 4 orders of magnitude higher than the water solubility limit. 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 2 mg/L." Furthermore, the acute toxicity of zinc dilaurate (C12) to Danio rerio is with a nominal 96-h NOEC of 10 mg/L above its water solubility limit of around 5 mg/L (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 (C12-C18) are not acutely toxic to fish.

Nevertheless, conservative read across to the assessment entities soluble zinc substances and C14-18 fatty acids is applied, since zinc cations and fatty acid anions determine the fate and toxicity in the environment. Since C14-18 fatty acids have a low potential for ecotoxicity, the hazard assessment of Fatty acids, C14-18 and C16-18-unsatd, zinc salt is based on zinc ions.

 

Fatty acid anions (C14-18-satd. and C16-18-unsatd.):

Fatty acids as contained in plant and animal tissue are a natural component of aquatic systems, represent a significant part of the nutritional demands of living organisms, are rapidly degraded and non-bioaccumulative and therefore of low toxic potential towards microorganisms.

 

Zinc:

The key data (lowest LC50 values) are summarised as follows:

- for Oncorrhynchus mykiss: 0.169 mg Zn/L (single value) at neutral/high pH and low hardness

- for Pimephales promelas (single values) at high hardness: 0.78 mg Zn/l and 0.33 mg Zn/l at low and neutral/high pH, respectively

Additional information

Information on fish toxicity of the structural analogue fatty acids, C16-18, zinc salts 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 and 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, behavioural abnormalities or mortality were not observed. Effects were also not observed at nominal concentrations of fatty acids, C16-18, zinc salts up to the water solubility limit in two further studies. These findings are further supported by acute aquatic toxicity data of a zinc salt of fatty acids with a shorter alkyl chain length and arelatively higher zinc content, i.e. zinc dilaurate, 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 EU Risk assessment on zinc distearate (Final report R074_0805_env, May 2008) and taken into account results of tests with the structural analogues fatty acids, C16-18, zinc salts and zinc dilaurate (C12), it is assumed that the toxicity of Fatty acids, C14-18 and C16-18-unsatd., zinc salts to fish is (far) above the water solubility limit of around 2 mg/L.