Fatty acids, C18-24, zinc salts

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that key and supporting source substance(s) and target substance have similar acute toxicity based on their structural similarity.

2. SOURCE AND TARGET CHEMICALS COMPOSITION
Source(s) and target are all fatty acid(s) zinc salts. They have a very close structural similarity only varying in their fatty acids chain length distribution and consequential minor variations in their relative zinc content.

2.1. Composition of key source substance zinc didodecanoate / 35674-68-1 / 219-518-5:
- zinc dilaurate / zinc didodecanoate / 2452-01-9 / 219-518-5: >=95.0 - <=100.0% (w/w)
- fatty acids, - fatty acids, >C12, zinc salts / fatty acids, >C12, zinc salts: <=5.0% (w/w)
- lauric acid / lauric acid / 143-07-7 / 205-582-1: <=2.0% (w/w)
- water / dihydrogen oxide / 7732-18-5 / 231-791-2: <=1.0% (w/w)
Only components which do not affect the classification may be present in the target substance.

2.2. Composition of supporting source substance Fatty Acids, C16-18, zinc salts / 2452-01-9 / 293-049-4:
- Fatty Acids, - zinc dipalmitate / zinc dihexadecanoate / 4991-47-3 / 225-652-5: >=20.0 - <=65.0% (w/w)
- zinc distearate / zinc dioctadecanoate / 557-05-1 / 209-151-9: >=35.0 - <=80.0% (w/w)
- Fatty Acids, >C18, zinc salts: <= 6.0% (w/w)
- Fatty acids, C16-18 / Fatty acids, C16-18 / 67701-03-5 / 266-928-5: <= 3.0% (w/w)
- water / dihydrogen oxide / 7732-18-5 / 231-791-2: <= 2.0% (w/w)
Only components which do not affect the classification may be present in the source substance.

2.3. Composition of target substance Fatty acids, C18-24, zinc salts / 84776-57-8 / 283-985-1:
- zinc distearate / zinc dioctadecanoate / 557-05-1 / 209-151-9: >=30.0 - <=45.0% (w/w)
- zinc diicosanoate / zinc diicosanoate / 7278-04-8 / 230-693-7: >=5.0 - <=15.0% (w/w)
- zinc didocosanoate / zinc didocosanoate / 16529-65-0 / 240-597-7: >=40.0 - <=55.0% (w/w)
- Zinc salts of fatty acids C24: <= 10.0% (w/w)
- Fatty acids, C18-24 / 98106-57-1 / 308-578-9: <= 5.0% (w/w)
- water / dihydrogen oxide / 7732-18-5 / 231-791-2: <= 2.0% (w/w)
Only components which do not affect the classification may be present in the target substance.

3. ANALOGUE APPROACH JUSTIFICATION
Source(s) and target have a very close structural similarity only varying in their fatty acids chain length distribution and consequential minor variations in their relative zinc content. They are produced by the oleochemistry sector, starting from natural fatty materials and consist of natural fatty acids and zinc. In the aquatic environment and the body, fatty acids zinc salts will partly dissociate into the zinc cation and the fatty acids anions. As zinc is an essential trace element and fatty acids are major nutrients, both moieties are effectively processed and regulated in the body. A minor variation in the fatty acid composition and the zinc amount of source(s) and target is not expected to substantially impact the systemic activity. The EC50 values for the acute toxicity of the analogue substances zinc dilaurate (zinc salt of a C12-fatty acid) and Fatty acids, C16-18, zinc salts to Danio rerio are > 10 mg/L and > 10,000 mg/L, respectively, and thus above the water solubility limit of substance Fatty acids, C18-24, zinc salts of 0.63 mg/L. Thus, zinc salts of shorter- and similar-chained fatty acids appear to have a low potential for acute toxicity to freshwater fish. A similar low potential is assumed for substance Fatty acids, C18-24, zinc salts, a zinc salt of similar- and longer-chained fatty acids (C18-24) with a lower zinc content and solubility.
Read-across of data available for zinc salts of shorter-chained (C12) and similar chained (C16-18) fatty acids based on structural similarity, water solubility and zinc content in a conservative, worst-case approach is assumed to adequately describe the toxicological potential of Fatty acids, C18-24, zinc salts.
Therefore, read-across from the existing short-term toxicity studies to fish on the source substance(s) is considered as an appropriate adaptation to the standard information requirements of Annex VII, 8.5.1 of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of the REACH Regulation.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across: supporting information

Reason / purpose for cross-reference:

read-across: supporting information

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mortality (fish)

Remarks on result:

other: read-across data on structural analogue Fatty acid, C12, zinc salt

Key result

Duration:

96 h

Dose descriptor:

LC100

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mortality (fish)

Remarks on result:

other:

Remarks:

read-across data on structural analogue Fatty acid, C12, zinc salt

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

mortality (fish)

Remarks on result:

other:

Remarks:

read-across data on structural analogue Fatty acid, C12, zinc salt

Conclusions:

The NOEC (96h) of the tested substance Zinc dilaurate is 10 mg/L. At all tested concentrations, including the highest nominal test concentration, neither behavioural abnormalities nor mortality occurred. It is concluded, that the acute toxicity of the zinc dilaurate to fish is above the water solubility limit of around 5 mg/l. Based on this data, also for the longer-chained substance Fatty acids, C18-24, zinc salts with a lower zinc content and solubility (0.63 mg/L as conservative value), missing short-term toxicity to fish up to and including the water solubility limit is expected.

Description of key information

Aquatic toxicity studies with substance Fatty acids, C18-24, zinc salts are not available. In the assessment of substance Fatty acids, C18-24, zinc salts, read-across to analogue substances and/or the assessment entities soluble zinc substances and fatty acids, C18-24 is conservatively applied since the ions of substance Fatty acids, C18-24, zinc salts determine its fate and toxicity in the environment.

The EC50 values for the acute toxicity of the analogue substances zinc dilaurate (zinc salt of a C12-fatty acid) and Fatty acids, C16-18, zinc salts to Danio rerio are > 10 mg/L and > 10,000 mg/L, respectively, and thus above the water solubility limit of substance Fatty acids, C18-24, zinc salts of 0.63 mg/L. Thus, zinc salts of shorter- and similar-chained fatty acids appear to have a low potential for acute toxicity to freshwater fish. A similar low potential is assumed for substance Fatty acids, C18-24, zinc salts, a zinc salt of similar- and longer-chained fatty acids (C18-24) with a lower zinc content and solubility. This is in agreement with the conclusion on short-term toxicity to fish of the EU risk assessment on the structural analogue zinc distearate (Fatty acids, C16-18, zinc salts, CAS-No.: 557-05-1 & 91051-01-3 EINECS-No.: 209-151-9 & 293-049-4) carried out within the framework of EU Existing Chemicals Regulation (EEC) No 793/93 (Final report R074_0805_env, May 2008) in which it is concluded, "that the toxicity of the substance Fatty acids, C16-18, zinc salts to fish is (far) above the water solubility limit of around 1 mg/L".

Considering the dissolved moieties upon dissolution, reliable data indicate that the moiety of ecotoxicological concern are zinc cations. The acute toxicity data further indicate that zinc salts of shorter- and similar-chained (C12-C18) fatty acids have a significantly lower aquatic toxicity than soluble zinc salts. It is therefore assumed that a high fraction of zinc from zinc salts of medium- and longer chained (>C12) fatty acids is not bioavailable. The ecotoxic potential of the fatty acid chain, i.e. fatty acids, C18-24, 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)).

The aquatic hazard assessment is based on the most toxic moiety, i.e. the zinc cation.

Key data (lowest LC50 values) for zinc are:

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

-for Pimephales promelas (single values): 0.780 mg Zn/l at low pH (high hardness) and 0.330 mg Zn/l at neutral/high pH, high hardness

-for Pimephales promelas: LC50 0.780 mg Zn/l (at low pH); 0.33mg Zn/l at neutral/high pH

Additional information

ANALOGUE SUBSTANCES FATTY ACID(S), C12 and C16-18, ZINC SALT(S):

- Fatty acid, C12, zinc salt (zinc dilaurate):

Information on acute fish toxicity is available from a study performed according to OECD Guideline 203. Fish (Danio rerio) were exposed for 96 hours to nominal concentrations of 0 (control), 0.1, 1, 10 mg/L under static conditions. At all tested concentrations, including the highest nominal test concentration, neither behavioural abnormalities nor mortality occurred. The acute toxicity of zinc dilaurate to fish is above the water solubility limit ranging from 5.2 to 6.4 mg/L.

- Fatty acids, C16-18, zinc salts:

Aquatic fish toxicity data on 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 old publication (Dowden, BF, Bennett, HJ 1965). None of the studies do fully comply with the requirements of the recent guidelines regarding performance and/or documentation. However, in accordance to the judgement given on the same set of data in the EU risk assessment of zinc distearate carried out within the framework of EU Existing Chemicals Regulation (EEC) No 793/93 (Final report R074_0805_env, May 2008), the total set of data is regarded as sufficient to come to a conclusion on the intrinsic aquatic fish toxicity of the substance. In accordance to Annex XI of Regulation (EC) No 1907/2006, the total set of data is used in a weight of evidence approach to fulfil REACH data requirements on aquatic fish toxicity. In the most reliable study (Henkel KGaA, 1995), the acute toxicity of Fatty acids, C16-18, zinc salts to fish was investigated according to EU Method C.1 (Acute Toxicity for Fish) in the former version of 1992. Fish (Danio rerio) were exposed for 96 hours to nominal concentrations of 0 (control), 1000, 3000 and 10000 mg/L under semi-static conditions. Up to and including the highest nominal test concentration neither behavioural abnormalities nor mortality occurred. Test was conducted at nominal concentrations far exceeding the water solubility by 3 to 4 orders of magnitude. Measures to disperse the test substance in the test water were used. The actual test concentrations were below the detection limit (1 mg/L) of the analytical method used. Therefore, a numeric value for the actually test concentrations cannot be given. However, due to the very high level of nominal test concentrations and the measures used to disperse the test substance in the test medium, it is very likely that the actual test concentrations included the water solubility limit which is in the range of 1 mg/L (c. f. EU risk assessment zinc distearate carried out within the framework of EU Existing Chemicals Regulation (EEC) No 793/93 (Final report R074_0805_env, May 2008)). No effects were observed at nominal Fatty acids, C16-18, zinc salts concentrations up to the water solubility limit in the two further studies either. In accordance to the evaluation given in the EU Risk assessment, from the results of these tests it is concluded, that the toxicity of the substance Fatty acids, C16-18, zinc salts to fish is (far) above the water solubility limit of around 1 mg/L.

Conclusions from 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):

"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 1 mg/L."

Please refer to the section for the respective assessment entity for data on the moieties. In brief:

ZINC:

Good quality and relevant data for 5 species. Tests were done according to standard protocol or equivalent.

Data are grouped per species according to

-pH: low (6 -<7) - neutral/high (7 -8.5)

-and hardness: low/medium (<100mg CaCO3/L) and medium/high (>100 mg CaCO3/L).

Key data (lowest LC₅₀values) are:

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

- for Pimephales promelas (single values): 0.780 mg Zn/L at low pH (high hardness) and 0.330 mg Zn/L at neutral/high pH, high hardness

- for Pimephales promelas: 0.780 mg Zn/L (at low pH); 0.33mg Zn/L at neutral/high pH

Fish are generally less sensitive to zinc than invertebrates and algae.

FATTY ACIDS, C18-24:

The ecotoxic potential of the fatty acid chain, i.e. fatty acids, C18-24, 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)).