Fatty acids, C18-24, zinc salts

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

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 source substances

2.1.1 Composition of 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.

2.1.2. Composition of 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 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)

2.3. 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. In a reliable study with the analogue substance zinc dilaurate (zinc salt of a C12-fatty acid), the EL10 and EL50 amount to 3.73 mg/L and 12.87 mg/L WAF for the acute toxicity to freshwater algae (Pseudokirchneriella subcapitata), respectively. The toxicity of a similar-chained (C16-18) fatty acids zinc salt to Pseudokirchneriella subcapitata is also low (EL10= 3.31 mg/L WAF, EL50 > 100 mg/L WAF fatty acids, C16-18, zinc salts). Thus, zinc salts of shorter- and similar-chained fatty acids appear to have a low potential for toxicity to freshwater algae. 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 algae 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 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

Reason / purpose for cross-reference:

read-across: supporting information

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

12.87 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat. (dissolved fraction)

Remarks:

recalculated from measured zinc

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

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

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat. (dissolved fraction)

Remarks:

recalculated from measured zinc

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

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

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

3.73 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat. (dissolved fraction)

Remarks:

recalculated from measured zinc

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

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

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

3.31 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat. (dissolved fraction)

Remarks:

recalculated from measured zinc

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

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

Conclusions:

In a reliable study with the analogue substance zinc dilaurate (zinc salt of a C12-fatty acid), the EL10 and EL50 amount to 3.73 mg/L and 12.87 mg/L WAF for the acute toxicity to freshwater algae (Pseudokirchneriella subcapitata), respectively. The toxicity of a similar-chained (C16-18) fatty acids zinc salt to Pseudokirchneriella subcapitata is also low (EL10= 3.31 mg/L WAF, EL50 > 100 mg/L WAF fatty acids, C16-18, zinc salts). Thus, zinc salts of shorter- and similar-chained fatty acids appear to have a low potential for toxicity to freshwater algae. 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.

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.

In a reliable study with the analogue substance zinc dilaurate (zinc salt of a C12-fatty acid), the EL10 and EL50 amount to 3.73 mg/L and 12.87 mg/L WAF for the acute toxicity to freshwater algae (Pseudokirchneriella subcapitata), respectively. The toxicity of a similar-chained (C16-18) fatty acids zinc salt to Pseudokirchneriella subcapitata is also low (EL10= 3.31 mg/L WAF, EL50 > 100 mg/L WAF fatty acids, C16-18, zinc salts). Thus, zinc salts of shorter- and similar-chained fatty acids appear to have a low potential for toxicity to freshwater algae. 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.

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:

acute toxicity to freshwater algae: lowest IC50 0.136 mg Zn/L (Selenastrum capricornutum; single value) (neutral/high pH)

chronic toxictiy to freshwater algae: lowest NOEC 0.019 mg Zn/L (Pseudokircherniella subcapitata =Selenastrum capricornutum; geomean of 27 data)

chronic toxicity to marine algae: 12 species available which NOECs range between 0.0078 and 0.67 mg/l (dissolved concentrations).

Additional information

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

- FATTY ACID, C12, ZINC SALT (zinc dilaurate):

In a growth inhibition test with P. subcapitata exposed to water accommodated fractions (WAF) of 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, the calculated EL50 value for growth rate was 12.87 mg/L (extrapolated) while the EL10 was 3.73 mg/L, based on WAF loadings.

- FATTY ACIDS, C16-18, ZINC SALTS:

In a growth inhibition test with P. subcapitata exposed to water accommodated fractions (WAF) of Fatty acid, C16-18, zinc salts at loadings of 0.01, 0.1, 1, 10 and 100 mg/L in standard test medium over a test period of 72 hours (Wenzel, 2013a), the calculated EL10 value for growth rate was 3.31 mg/L (extrapolated) based on WAF loadings while the EL50 is expected to be > 100 mg/L based on WAF loadings.

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

ZINC:

Acute freshwater toxicity tests of high quality and relevancy performed according to standard protocol. Information is on 1 species which is in both the acute and chronic aquatic database on zinc the most sensitive. The lowest IC50 value is taken as reference value for classification for acute effect at neutral/high pH.

Chronic freshwater toxicity tests of high quality and relevancy according to standard protocol or equivalent. Data on 2 species, one of which the most sensitive of all freshwater organisms, second species is less sensitive.

Chronic seawater tests of high quality and relevancy according to standard protocol or equivalent. Data on 12 species, for which 3 species are in the low part of the species sensitivity distribution. One species of macro-algae is the second most sensitive of all seawater organisms.

- acute toxicity to freshwater algae: lowest IC50 0.136 mg Zn/L (Selenastrum capricornutum; single value) (neutral/high pH)

- chronic toxictiy to freshwater algae: lowest NOEC 0.019 mg Zn/L (Pseudokircherniella subcapitata =Selenastrum capricornutum; geomean of 27 data)

- chronic toxicity to marine algae: 12 species available which NOECs range between 0.0078 and 0.67 mg/l (dissolved concentrations)

Algae are considered the most sensitive aquatic species to zinc.

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)).