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The aquatic toxicity of the alcohol ethoxylates (AE) has been extensively evaluated in numerous studies on fish, daphnids and algae as well as microorganisms.

Studies for acute toxicity of alcohol ethoxylates on fish, daphnids and algae are available for CAS 68439-50-9, 66455-14-9, 68131-39-5 and partly CAS 68213-23-0 (fish) and CAS 68920-66-1 (daphnids and algae).

The majority of the studies were conform to OECD and/or EC-guidelines and were partly GLP compliant.

In addition chronic studies are available for CAS 68131-39-5 (daphnids) and for an alcohol ethoxylate mixture of C12 -13 (fish; literature data - no CAS defined). Both studies are used to describe chronic toxicity of alcohol ethoxylates for the whole category.

Regarding acute toxicity of alcohol ethoxylates the values are within the same range for all studies available and ranged from 0.1 - 1.0 mg/L for the three trophic levels (fish, invertebrates and algae), with some exception regarding CAS 68920-66-1 were lower toxicity is observed in the two available studies on daphnids and algae. Nevertheless the mixture given in CAS 68439-50-9 is regarded as worst-case and thus is used for read-across for several CAS were no studies are available for certain endpoints.

For the C12 -15 alcohol ethoxylate mixture short-term studies on freshwater species of three trophic levels (fish, invertebrates and algae) are available. In addition a chronic toxicity test on fish is available for the C12 -15 alcohol ethxoylate mixture with a degree of ethoxylation of 7 moles EO. To cover the chronic daphnid endpoint a publication of a test with a C12-13 mixture is used. As described for the chronic fish test, the chronic daphnid test also is conducted with an alcohol ethoxylation mixture containing a mean of 6.5 moles EO.

To determine the differences in toxicity depending on the degree of ethoxylation, acute daphnid endpoints available for the category member, the alcohol ethoxylate mixture C12 - 14 (1EO - 7EO) were considered. The available EC50-values for that mixture containing different ethoxy-chain lengths vary by a factor of 2.6 at maximum (EC50 for EO7 / EC50 for EO2). The mixture containing a mean of 2EO represents the worst-case. By taking into account the factor of 2.6 and the available NOEC given in the chronic daphnid study (NOEC = 0.77 mg/L), a comparable mixture with 2 ethoxy-groups would, for example, result in a NOEC-value of approximately 0.30 mg/L. For fish no correlation between increasing degree of ethoxylation and decreasing toxicity could be determined regarding available data.

To further consider the chronic risk of alcohol ethoxylates (AE) to aquatic organisms, endpoints available for long chain alcohols (LCA), representing the parent substances of AE, were reviewed on the basis of OECD SIDS for long chain alcohols (2006). A consideration of the LCA is valid as normally 15-50% of the alcohol ethoxylate mixtures are represented by free unethoxylated alcohols. Chronic endpoints listed in the OECD SIDS (2006) were generally within the same range as the NOEC-values reported for members of the alcohol ethoxylate category. By taking into account all available information for long chain alcohols and alcohol ethoxylates it can generally be concluded that chronic risk will be in the range of 0.01 - 1.0 mg/L (NOEC-values), depending on the chain length distribution of a mixture.

Comparing acute and chronic data available for algae, daphnids and fish for the category members of alcohol ethoxylates, normally algae are determined to be the most sensitive species, in case of the C12 -15 mixture the lowest EC50 -value could be determined for daphnids (EC50 = 0,.14 mg/L). Thus in case of CAS 68131 -39 -5, for classification, the daphnid endpoint needs to be considered. Nevertheless the risk assessment (PNEC-calculation) is not based on the worst-case assumption as a wide dataset of chronic endpoints is available for aquatic organisms. These values were summarized by Belanger et al. (2006) and the HERA-report (2009) on ethoxylated alcohols. Belanger et al. (2006) listed the chronic ecotoxicity of alcohol ethoxylates for 17 aquatic species conducted in 60 tests. Chronic tests used for HC5-calculation of Belanger et al (2006) were conduced with invertebrates of different taxa, like crustaceans (Daphnia magna and Ceriodaphnia dubia), insects (Chironomus tentans), molluscs (the bivalvia species Corbicula fluminea and the gastropod species Elimia livescens), rotifers (Brachionus calyciflorus) and planarians (Dugesia gonocephala). In case of algae, tests on three different green algae species, one diatom species and one blue-algae species are available and were used for HC5-calcluation. Fish tests taken into account for HC5-calculation were conducted with rainbow trout, fathead minnow and bluegill (most species tested in several tests). As one representative of higher plants, a study of the aquatic macrophyte Lemna minor is used.

By using these data the authors first determined EC10-values from the initial test data (i. e. NOEC-values) per endpoint and species. In a second step specific QSAR-models were used to predict toxicity of tested distributions and then toxicity of all pure homologues of alcohol ethoxylates. After construction of a matrix of normalized EC10-values per species, HC5-values were calculated by using the method of Aldenberg and Jaworska (2000). The resulting matrix contains HC5-values for pure homologues of chain lengths C9 to C18 ethoxylated with 0 - 18 ethoxy-groups. These HC5-values were used for the refined calculation of PNEC-values for the alcohol ethoxylate mixtures to be registered. To consider the toxicity of CAS 68131-39-5, representing a mixture of C12-C15 with 1 - 2.5EO, chain length distribution (9 - 32% C12, 14 - 43% C13, 13 - 49% C14 and 12 - 33% C15) and a degree of ethoxylation of 1 were taken into account. Mixture toxicity is then calculated according to the formula of Finney (1942). Therefore, respectively, minimal and maximal content of a certain pure alcohol ethoxylate available in the mixture is used. In a second step an arithmetic mean of all values is prepared which is used as HC5-value for the mixture. For CAS 68131 -39 -5 a HC5 of 0.0446 mg/L could be determined. According to the guidance document chapter R.10 an HC5-value normally can be used for PNEC-calculation by taking into account assessment factors of 5 - 1. For a further reduction of the assessment factor several criteria need to be fulfilled. According to Belanger et al. (2006) and HERA-report (2009) these criteria, which correspond with the requirements given in the EU TGD (2003) are fulfilled for the data used for the HC5-calculation. HERA-report (2009) listed a detailed justification of an assessment factor of 1 concluding that the confidence of the data used by Belanger et al. (2006) is so high that no further assessment factor is necessary to determine the PNEC freshwater.

Concerning the marine environment, the guidance document chapter R.10 (ECHA, 2008) states that "no marked differences in sensitivity between freshwater and saltwater biota appears that systematically applies across all three trophic levels considered. Differences between trophic levels within each medium were generally as significant or even more marked than between media" (ECHA, 2008, chapter R.10). The fact that no marked difference in sensitivity between freshwater and saltwater biota occur, could be proved for alcohol ethoxylates. For CAS 68131 -39 -5, only freshwater data are available for fish, invertebrates and algae. According to the guideline R.10 in such case PNEC-values should be derived from the most sensitive endpoint regardless of the medium. In case of the alcohol ethoxylates it seems thus valid to use the HC5-value calculated for the wide set of different freshwater species also for the marine compartment with an assessment factor of 5.

References: Aldenberg, T., Jaworska, J. (2000).Uncertainty of the hazardous concentration and fraction affected for normal species sensitivity distributions. Ecotoxicol. Environm. Saf. 46, 1 -18.

Belanger, S. E., Dorn, P. B., Toy, R., Boeije, G., Marshall, S. J., Wind, T., van Compernolle, R. and Zeller, D. (2006). Aquatic risk assessment of alcohol ethoxylates in North America and Europe. Ecotoxicology and Environmental Safety 64, 85-99.

ECHA - European Chemical Agency (2008). Guidance on information requirements and chemical safety assessment. Chapter R.10: Characterisation of dose[concentration]-response for environment. May, 2008.

Finney, D. F. (1942). The analysis of toxicity tests on mixtures of poisons. Ann. Appl. Biol. 29, 82–94.

HERA - Human & Environmental Risk Assessment on ingredients of European household cleaning products (2009). Alcohol Ethoxylates. Version 2.0, September, 2009.

OECD SIDS (SIDS Initial Assessment Report for22). Category Long Chain Alcohols. April, 2006.