Rhamnolipids: fermentation products of glucose with Pseudomonas putida, Pseudomonadaceae

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Data waiving:

other justification

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Description of key information

The purpose of the attached document is to provide a scientific weight of evidence (WoE) argument to waive the fish chronic testing for the material Di-Rhamnolipids (Di-RLs) under the European REACH (Regulation (EC) No 1907/2006 regulation. This WoE includes: 1) acute to chronic ratio (ACR), supported by Mode / Mechanism of Action (MoA/MechoA) identification and QSAR predictions; 2) modelled demonstration of low environmental exposure and low risk for use of Di-RLs in ChinEuropa. Evonik have completed all aquatic ecotoxicological studies, except for a fish chronic study. The ingredient is readily biodegradable, passing the 10-day window and 92% removal in sewage treatment plants (STPs) is estimated using the Chesar.  Measured physicochemical data demonstrates the material is soluble in water (353 g/L), will remain in the water phase (log Kow: -0.247) and will be fully ionized at environmental pH.

ACRs are used widely in environmental risk assessment as an approach to estimate the chronic toxicity of )chemicals in aquatic organisms where chronic toxicity are unavailable. Using in silico approaches, the weight of evidence (WoE) indicates that Di-RLs act with a membrane-based narcosis mode of action – either baseline (non-polar) narcosis or ester narcosis.  Both mechanisms were reviewed when predicting aquatic toxicity to support the ACR value derivation using experimental data. We reviewed general ACRs derived using experimental data for a broad spectrum of chemicals as well as those ACRs for relevant MOA and chemical class. Here we have evaluated a representative value based on the surfactant class. An ACR value of 7.7 representing a 90th percentile value was selected from experimental data and is considered appropriate for representing this scenario. These were further supported by ACRs derived from QSAR toxicity predictions using the ECOSAR and EU TGD approaches and also consistent with other reported surfactant ACRs used in ECOSAR.

Using the available fish acute toxicity value of 75mg/L, with the ACR of 7.7 provides us with an estimated representative fish chronic values of 9.7  mg/L.

Using the Chesar model an environmental risk assessment was subsequently completed using a proposed 100-1000 tonnes/year in Europa and two Predicted No Effect Concentration (PNEC) scenarios: 1) Daphnia chronic value (EC10 34.27 mg/L) and assessment factor of 100, 2) Representative ACR Fish Chronic Value (9.7 mg/L) and assessment factor of 10. On running the model, the two PNEC scenarios passed the risk assessment (RCR < 1). In addition, no in-river removal has been assumed as a conservative approach for the risk assessment. However, in reality and based on the ready biodegradation result as well as evidence from other surfactants, there would be expected to be significant in-river removal.

In conclusion, we are of the opinion that completing a chronic fish study would not provide value to the environmental risk assessment when there is confidence in the ACR approach to reliably predict the chronic fish toxicity and that the overall risk assessment approach is conservative and still favourable.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

EC10

Effect concentration:

9.7 mg/L