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Long-term toxicity to aquatic invertebrates

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Description of key information

No toxicological effects on aquatic invertebrates were observed up to the limit of water solubility of Fatty acids, C16-18 and C18-unsatd., branched and linear regarding mortality and reproduction (NOELR  >= 5 mg/L Daphnia magna).

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Additional information

One study is available on the long-term toxicity of Fatty acids, C16-18 and C18-unsaturated, branched and linear, “Monomer acid” (CAS No. 68955-98-6) to aquatic invertebrates. The study was conducted according to the OECD guideline 211 under GLP conditions. As the test substance is a UVCB and poorly soluble in water, the test solutions were prepared as water accommodated fractions (WAF) with differential loadings. The test organism Daphnia magna was exposed to the test substance at loadings of 0.1, 0.5, 1.25 and 5.0 mg/L for 21 days. The analytical monitoring of the test concentrations showed that the test substance was present in the test solutions and that the WAFs were stable. Based on preliminary media preparation trials, 5.0 mg/L was the highest concentration at which a stable WAF could be obtained. However, as the test substance is a poorly soluble UVCB substance, the fatty acid cluster of the original test item differs from the soluble part in the WAF fraction, due to the different solubilities of the constituents. Therefore, as the analytical concentrations do not reflect the concentration of the original test substance, they cannot be used to derive effect values.

No significant effect on reproduction was observed in any of the treatment groups. The NOELR for both cumulative number of offspring and age at first brood was determined to be ≥ 5.0 mg/L.

The effect of the test substance on the length of the daphnids was significant at the three highest test concentrations. However, the observed reduction in growth was very small and obviously only turned out to be significant due to the very consistent length of the animals (low standard deviation) from the lowest treatment and the control groups. Additionally, as stated in the ECHA guidance, the purpose of the test is to determine the effect of the test substance on the reproductive output and the ecologically most relevant response variable is the total number of living offspring produced per parent animal. The hazard assessment is therefore based on the NOELR for reproduction. Moreover, the EC10 for length is also > 1 mg/L and thus does not influence classification.