Ecotoxicity
Following the Read-Across Assessment Framework (RAAF), the read-across approach for ecotoxicity endpoints is described in scenario 6 (different compounds have quantitatively similar properties) and governed by AE 6.3 (common underlying mechanism, quantitative aspects).
Considering the structural and physico-chemical properties of the substances, acrylic acid has a different profile compared to the six acrylate esters included in the read-across approach for aquatic toxicity. Similarly, existing aquatic toxicity data demonstrates differences between the aquatic hazard profile of acrylic acid and the acrylate esters. While the available data indicates aquatic toxicity at the same order of magnitude across all three trophic levels for all acrylate esters within the category, acrylic acid is an outlier to this trend as it displays a somewhat different level of toxicity. It can be concluded that read-across among the acrylate esters is applied with a high level of certainty. An overview of the ecotoxicity information on acrylate esters is provided below. For comparison the acrylic acid ecotoxicity data is also included.
Data for algae are available for all substances in the category. The available data are derived from studies of appropriate duration and quality to warrant a high degree of reliability and accordingly have Klimisch reliability ratings of 1 and 2, respectively.
Short-Term Toxicity to fish - The results of all studies on short-term toxicity to fish conducted on the esters yielded similar results across all substances within the category for both freshwater (LC50s 1.8 – 5.2 mg/L) and marine (LC50s 1.1 – 2.1 mg/L) species, supporting the broader use of the category approach. Short-term toxicity studies for freshwater fish are available for all substances. For marine fish, read-across from data on the short-term toxicity testing of MA, EA and n-BA is considered a valid approach to address the endpoint for the other substances (i-BA, t-BA, 2EHA).
Long-Term Toxicity to Fish - Acute effect levels were determined to be in the same concentration range for all three trophic levels, with algae, invertebrates and fish presenting similar sensitivity. It is considered that a similar trend would be observed for long-term effects, which is supported by the available long-term toxicity data for testing on invertebrates and algae. As such, the available information on long-term toxicity to algae and aquatic invertebrates was considered to be conservative to assess long-term toxicity towards aquatic organisms. Further testing on fish (as vertebrate animals) is, therefore, not necessary or justified. Similarly, the need to demonstrate the suitability of read-across within the category for this endpoint is not considered necessary at this time.
Short-Term Toxicity to Aquatic Invertebrates - The results of all studies conducted on the esters yielded similar results across all substances within the category for both freshwater (EC50s 1.3 – 8.8 mg/L) and marine (1.6 mg/L) species, supporting the broader use of the category approach. Read-across to data on the toxicity of the substances to marine species is not technically required but the use of data on MA to address the endpoints for other substances is considered valid.
Long-term Toxicity to Invertebrates - Given that the results of all studies across all three trophic levels are broadly in the same range, and that there is no marked difference in aquatic toxicity among any of the acrylate esters within the category, it is concluded that this trend would occur also for long-term toxicity to aquatic invertebrates. The available long-term Daphnia studies conducted on the acrylate esters yielded very similar results (NOECs 0.16 – 0.85 mg/L), supporting the use of the category approach. Thus, it is considered justified to read-across from the data on testing of EA, n-BA and 2EHA to address this endpoint for the other category substances. Read-across is applied with a high level of confidence.