Fatty acids, C18-24, zinc salts

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

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 Fatty Acids, C16-18, zinc salts / 91051-01-3 / 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.

2.2. Composition of supporting source substances

2.2.1. Composition of supporting source substance zinc bis[12-hydroxyoctadecanoate] / 35674-68-1 / 252-669-5:
- zinc bis[12-hydroxyoctadecanoate] / 35674-68-1 / 252-669-5: >=80.0 - <=100.0% (w/w)
- zinc distearate / zinc dioctadecanoate / 557-05-1 / 209-151-9: <=15.0% (w/w)
- zinc dipalmitate / zinc dihexadecanoate / 4991-47-3 / 225-652-5: <=4.0% (w/w)
- zinc dioleate / zinc dioctadec-9-enoate / 557-07-3 / 209-154-5: <=3.0% (w/w)
- zinc diricinoleate / zinc bis(12-hydroxyoctadec-9-enoate) / 13040-19-2 / 235-911-4: <=3.0% (w/w)
- zinc didocosanoate / zinc didocosanoate / 16529-65-0 / 240-597-7: <=1.0% (w/w)
- 12-hydroxystearic acid / 12-hydroxyoctadecanoic acid / 106-14-9 / 203-366-1: <=4.0% (w/w)
- stearic acid / stearic acid / 57-11-4 / 200-313-4: <=1.0% (w/w)
- water / dihydrogen oxide / 7732-18-5 / 231-791-2: <=1.0% (w/w)

2.2.2. Composition of supporting 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.

2.3. 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), zinc bis(12-hydroxyoctadecanoate) (zinc salt of a C18-fatty acid with an additional OH-group) and Fatty acids, C16-18, zinc salts to Daphnia magna are > 10 mg/L, > 1000 mg/L and > 100 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 invertebrates. 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 aquatic invertebrates 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:

data waiving: supporting information

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: at pH 6

Remarks:

read-across data on structural analogue substance Fatty acid, C16-18, zinc salts

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: at pH 8.1

Remarks:

read-across data on structural analogue substance Fatty acid, C16-18, zinc salts

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 1.1 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element (dissolved fraction)

Remarks:

zinc

Basis for effect:

mortality

Remarks on result:

other: at pH 6

Remarks:

read-across data on structural analogue substance Fatty acid, C16-18, zinc salts

Key result

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

> 0.95 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

element (dissolved fraction)

Remarks:

zinc

Basis for effect:

mortality

Remarks on result:

other: at pH 8.1

Remarks:

read-across data on structural analogue substance Fatty acid, C16-18, zinc salts

Conclusions:

The toxicity of the test substance Fatty acids, C16-18, zinc salts to daphnia is (far) above the water solubility limit of around 1 mg/L at pH 6 and pH 8.1. An EC50 could not be calculated because the test substance proved to be non-toxic (EC50 > maximum water solubility). The NOEC values are the highest concentrations tested showing no effect throughout the exposure time, being a nominal loading of 100mg/L and dissolved zinc concentrations of 1.1 and 0.95 at pH 6 and pH 8, respectively. 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 aquatic invertebrates 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), zinc bis(12-hydroxyoctadecanoate) (zinc salt of a C18-fatty acid with an additional OH-group) and Fatty acids, C16-18, zinc salts to Daphnia magna are > 10 mg/L, > 1000 mg/L and > 100 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 invertebrates. 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 toaquatic invertebrates 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, "The acute toxicity of zinc distearate to the waterflea Daphnia magna was determined according to OECD 202 in M7 medium at pH 6 and 8 (see also Chapter 1). Up to a loading rate of 100 mg zinc distearate/L the EC₅₀was not reached. The zinc concentration (detected using ICP-MS) at the beginning of the test was 1.2 mg Zn/L at pH 8 and 0.8 mg Zn/L at pH 6, at a loading rate of 100 mg zinc distearate/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 Ceriodapnia dubia: 0.413 mg Zn/L (single value) at low pH and low hardness

-for Ceriodapnia dubia: >0.53 mg Zn/L (single value) at low pH and high hardness

-for Ceriodapnia dubia: 0.147 mg Zn/L (geomean value) at neutral/high pH and low hardness

-for Ceriodapnia dubia: 0.228 mg Zn/L (geomean value) at neutral/high pH and high hardness

Additional information

ANALOGUE SUBSTANCES FATTY ACID(S), C12, C18OH and C16-18, ZINC SALT(S):

- Fatty acids, C16-18, zinc salts:

The acute toxicity of Fatty acids, C16-18, zinc salts to the waterflea Daphnia magna at pH 6 and 8 was not reached up to and including a loading rate of 100 mg Fatty acids, C16-18; zinc salts/L; the EC50 is > 100 mg/L. Thus, the toxicity to Daphnia magna is (far) above the water solubility limit of around 1 mg/L and Fatty acids, C16-18, zinc salts is not expected to be an acute hazard to aquatic invertebrates.

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):"

The acute toxicity of zinc distearate to the waterflea Daphnia magna was determined according to OECD 202 in M7 medium at pH 6 and 8 (see also Chapter 1). Up to a loading rate of 100 mg zinc distearate/L the EC₅₀ was not reached. The zinc concentration (detected using ICP-MS) at the beginning of the test was 1.2 mg Zn/L at pH 8 and 0.8 mg Zn/L at pH 6, at a loading rate of 100 mg zinc distearate/L."

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

The toxicity of zinc dilaurate to Daphnia magna is above the water solubility limit ranging from 5.2 to 6.4 mg/L; an EC50 was not reached up to 10 mg zinc dilaurate/L.

- Fatty acid, C18OH (Zinc bis[12 -hydroxyoctadecanoate]):

In a screening study on zinc bis[12-hydroxystearate] an EC50 was not reached at a nominal loading of 1000 mg/L.

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

ZINC:

Many good quality and relevant data for 5 standard 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).

Ceriodaphnia dubia is for all test conditions the most sensitive species.

Key data (lowest EC50 values) are:

-for Ceriodapnia dubia: 0.413 mg Zn/L (single value) at low pH and low hardness

-for Ceriodapnia dubia: >0.53 mg Zn/L (single value) at low pH and high hardness

-for Ceriodapnia dubia: 0.147 mg Zn/L (geomean value) at neutral/high pH and low hardness

-for Ceriodapnia dubia: 0.228 mg Zn/L (geomean value) at neutral/high pH and high hardness

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)).