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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
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:
other: QSAR model predicts invertebrate immobilisation consitent with OECD 202
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".
Deviations:
not applicable
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:
48 h
Dose descriptor:
EC50
Effect conc.:
1.5 mg/L
Nominal / measured:
estimated
Conc. based on:
other: UCVB constituent with lowest predicted effective concentration
Basis for effect:
mobility
Remarks on result:
other: Predicted using QSAR
Reported statistics and error estimates:
See attached QSAR documents
Validity criteria fulfilled:
yes
Conclusions:
The 48-hour EC50 for aquatic invertebrates (Daphnia magna) is predicted to be 1.5mg/L by the Danish (Q)SAR Database battery of two aquatic toxicity models.
Executive summary:

Acute toxicity to aquatic invertebrates (Daphnia magna) was predicted using a battery of two (Q)SAR models developed by the Danish National Food Institute at the Technical University of Denmark. Five individual constituents of the UVCB substance were within the applicability domain of the model. These constituents, along with water, comprise ca. 96% of the quantified constituents and ca. 75% of the total UVCB composition. The model predicts the most conservative effective concentration to be 1.5 mg/L for the palmitoleic acid constituent of the substance. This constituent comprises up to 20% of the UVCB composition. 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 48-hour EC50 for aquatic invertebrates (Daphnia magna) is predicted to be 1.5mg/L by the Danish (Q)SAR Database model battery.

Endpoint:
short-term toxicity to aquatic invertebrates
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:
other: QSAR model predicts invertebrate immobilisation consitent with OECD 202
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:
48 h
Dose descriptor:
LC50
Effect conc.:
ca. 7.9 mg/L
Nominal / measured:
estimated
Conc. based on:
other: UVCB constituent with the lowest predicted enpoint value
Basis for effect:
not specified
Remarks on result:
other: Predicted using QSAR
Reported statistics and error estimates:
See attached QMRF document.
Validity criteria fulfilled:
yes
Conclusions:
The 48-hour LC50 for aquatic invertebrates (Daphnia) is predicted to be 7.9mg/L by the ECOSAR model.
Executive summary:

The 48-hour acute toxicity LC50 for aquatic invertebrates (Daphnia) was estimated using the U.S. EPA ECOSAR predictive model. The model was queried for eight constituents of the UVCB substance which, 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, seven of the constituents are predicted to not be sufficiently soluble to exert acute toxicity effects on aquatic invertebrates after 48 hours. The value of the remaining constituent is determined to be the predicted LC50 for the UVCB substance. Therefore, the 48-hour LC50 for aquatic invertebrates (Daphnia) is predicted to be 7.9mg/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 invertebrates (Daphnia) was predicted for eight (8) individual constituents of the UVCB substance using the ECOSAR version 2.0.  The 48-hour LC50 for aquatic invertebrates is predicted to be 7.9mg/L based on the lowest individual constituent value predicted.

Acute toxicity of [ω-hydroxy-C16 (saturated and unsaturated) and C16 (unsaturated)] fatty acids to aquatic invertebrates (Daphnia magna) was predicted using a battery of (Q)SAR models developed by the Danish National Food Institute at the Technical University of Denmark.  The 48-hour EC50 for aquatic invertebrates is predicted to be 1.5mg/L based on the lowest individual constituent value predicted.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
1.5 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 48-hour EC50 value 1.5mg/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