[ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

March, 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRF and QPRF documents.

Qualifier:

equivalent or similar to guideline

Guideline:

other: QSAR predicts growth inhibition consistent with OECD guideline 201

Version / remarks:

Use of QSAR model is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Principles of method if other than guideline:

Use of QSAR model is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

10.3 mg/L

Nominal / measured:

estimated

Conc. based on:

other: UVCB constituent with lowest predicted effective concentration

Basis for effect:

growth rate

Remarks on result:

other: Predicted using QSAR

Reported statistics and error estimates:

See attached QSAR documents

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour EC50 for aquatic algae is predicted to be 10.3mg/L by the Danish QSAR Database model battery.

Executive summary:

Acute toxicity to aquatic algae (Pseudokirchneriella s.) was predicted using a QSAR model battery developed by the Danish National Food Institute at the Technical University of Denmark. Aquatic toxicity was predicted for seven individual constituents which, along with water, comprise more than ca. 98% of the quantified UVCB constituents and ca. 77% of the total composition. The most conservative predicted EC50 is 10.3 mg/L associated with the octadecanoic acid constituent. However, all of the constituents within the applicability domain of the model have predicted water solubility limit below the predicted EC50 endpoint. Although the predicted effective concentration for acute aquatic toxicity may not be observable at concentrations relevant to the solubility of each constituent, using the lowest predicted value provides the most conservative application of the predictive modelling results. Therefore, the 72-hour EC50 for aquatic algae is predicted to be 10.3mg/L by the Danish QSAR Database model battery.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

March, 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRF and QPRF documents.

Qualifier:

equivalent or similar to guideline

Guideline:

other: QSAR predicts growth inhibition consistent with OECD guideline 201

Version / remarks:

Use of QSAR model is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Principles of method if other than guideline:

Use of QSAR model is consistent with ECHA "Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals".

Test organisms (species):

other:

Key result

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

ca. 3.6 mg/L

Nominal / measured:

estimated

Conc. based on:

other: UVCB constituent with the lowest predicted endpoint value

Basis for effect:

not specified

Remarks on result:

other: Predicted using QSAR

Reported statistics and error estimates:

See attached QSAR documentation

Validity criteria fulfilled:

yes

Conclusions:

The 96-hour EC50 for aquatic algae is predicted to be 3.6mg/L by the ECOSAR model.

Executive summary:

Acute toxicity to aquatic algae was predicted for eight individual constituents of the UVCB substance using the U.S. EPA ECOSAR (Ecological Structure-Activity Relationship) Class Program version 2.0. These components, along with water, comprise more than ca. 98% of the quantified constituents and ca. 78% of the total UVCB composition. Although all constituents were within the applicability domain of the model, four of the constituents are predicted to not be sufficiently soluble to exert acute toxicity effects on aquatic invertebrates after 96 hours. The most conservative EC value of the remaining constituents is determined to be the predicted EC50 for the UVCB substance. The 96-hour EC50 for aquatic algae is predicted to be 3.6mg/L by the ECOSAR model.

Description of key information

Acute toxicity of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids to aquatic algae was predicted for eight (8) individual constituents of the UVCB substance using ECOSAR version 2.0.  The 96-hour EC50 value is predicted to be 3.6mg/L for green algae by the ECOSAR model.

Acute toxicity of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids to aquatic algae (Pseudokirchneriella s.) was predicted using a battery of (Q)SAR models developed by the Danish National Food Institute at the Technical University of Denmark.  The 72-hour EC50 value for algae is predicted to be 10.3mg/L by the Danish (Q)SAR Database battery aquatic toxicity models.

Key value for chemical safety assessment

EC50 for freshwater algae:

3.6 mg/L

Additional information

[ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids is a UVCB substance of biological origin.  The substance is a complex mixture of long-chain fatty acids produced and excreted by an engineered Escherichia coli K-12 organism through an aqueous microbial fermentation process.  The fatty acids are extracted from the fermentation broth using a solvent and separated from the cellular biomass by centrifugation.  The solvent is then evaporated, leaving the purified UVCB product.

The substance is predominantly comprised of linear unbranched long-chain organic fatty acids differentiated only by saturation and number of terminal carboxyl or hydroxyl groups.  All of the quantified constituents are comprised of only carbon, hydrogen, and oxygen.  The UVCB constituents are extracted from an aqueous broth into the solvent phase and separated by centrifugation.  Thus, the production process selects for constituents with similar physical properties and solubility characteristics.

Many of these components are naturally occurring within aquatic biological systems.  The major constituents of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids have been positively identified in numerous wild-type algae species [1,2,7].  These long-chain fatty acids, which include palmitic acid, palmitoleic acid, stearic acid, and oleic acid, are naturally produced by algae and are the subject of ongoing efforts to harvest and convert algal oils into biofuels [3,4,5].   Saturated and unsaturated long-chain fatty acids have also been identified in the tissues of numerous fish species [6].

The weight of evidence provided by the body of literature demonstrating the ubiquity of naturally occurring long-chain fatty acids in aquatic organisms and the results of two predictive QSAR models is sufficient to estimate the short-term toxicity to aquatic invertebrates of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids.  The most conservative endpoint prediction is determined to be the 96 -hour EC50 value 3.6mg/L.  This endpoint value is above the classification threshold according to the Regulation (EC) No 1272/2008 on classification, labelling and packaging of items and mixtures.  The substance is classified as a Category 2 short-term aquatic hazard according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations (2015) (including all amendments).

References:

1.       Cardoso C, Ripol A, Afonso C, et al. Fatty acid profiles of the main lipid classes of green seaweeds from fish pond aquaculture. Food Sci Nutr. (2017) 5:1186–1194

2.       El-Kassas, H. Growth and fatty acid profile of the marine microalga Picochlorum Sp grown under nutrient stress conditions. Egyptian Journal of Aquatic Research (2013) 39: 233-239

3.       Hassain, J, et al. Effects of Different Biomass Drying and Lipid Extraction Methods on Algal Lipid Yield, Fatty Acid Profile, and Biodiesel Quality. Appl Biochem Biotechnol (2015) 175: 3048

4.       Jeong, GT., Park, DH. Optimization of lipid extraction from marine green macro-algae as biofuel resources. Korean J. Chem. Eng. (2015) 32: 2463-2467

5.       Mostafa, S, El-Gendy, N. Evaluation of fuel properties for microalgae Spirulina platensis bio-diesel and its blends with Egyptian petro-diesel. Arabian Journal of Chemistry (2017) 10: S2040-S2050

6.       Ozogul Y, Ozogul F, Cicek E, Polat A, Kuley E: Fat content and fatty acid compositions of 34 marine water fish species from the Mediterranean Sea. International Journal of Food Science Nutrition 2008, 29:1-12

7.       Silva, G, et al. Distinct fatty acid profile of ten brown macroalgae. Brazilian Journal of Pharmacognosy (2013) 23(4): 608-613