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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Acute fish toxicity studies have not been carried out directly with registered substance, the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated.  However, read-across “analogue” data for two of the main constituents, namely, 1-decene dimer, hydrogenated (CAS No. 68649-11-6)(C20) and 1-decene dimer with dodecene, hydrogenated (CAS No. 151006-58-5)(C22) have been reported.
Using an analogue approach, read-across results from the short-term toxicity studies in rainbow trout and sheepshead minnow with C20-C22 substances indicate that the registered substance (the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated) would not be expected to cause toxicity in fish at the maximum loading in the WSF solutions or OWD solutions investigated in these tests (i.e., assumed to be at the maximum water solubility limit). The use of NOEL values reported in the table above in risk assessment is inappropriate as these values are not true NOECs as discussed in CSR Section 7.1.1. The low water solubility of the registered substance and the detection limitations of the analytical method preclude the determination of measurable levels in the water samples.

Key value for chemical safety assessment

Additional information

The read-across substance, 1-decene dimer hydrogenated (C20) has been evaluated for acute toxicity in sheepshead minnow in saltwater (MobilEnvironmental and Health Science Laboratory, 1992b). At loadings up to 5003 mg/L, no mortality was observed. The 96-hr LL50 was determined to be greater 5003 mg/L and the 96-hr NOEL was greater than 5003 mg/L. In addition, the read-across substance, 1-decene dimer with dodecene, hydrogenated (C22) has been evaluated for toxicity in rainbow trout (Salmo gairdneri) in freshwater. The water soluble fraction (WSF) solutions of the 1-decene dimer with dodecene hydrogenated did not cause any acute toxicity (i.e., mortality) rainbow trout. No adverse or behavioral effects were observed in this freshwater fish (96hr NOEL > 1000 mg/L WSF loadings) (ABC Laboratories, 1989a). Overall, based on read-across “analogue” data for the C20-C22 components, the reaction products of 1-decene, 1-dodecene and 1-octene, hydrogenated would not be acutely toxic to fish at the maximal water solubility.

 

Read-across Justification (analogue approach):

 

Several criteria justify the use of the read-across approach to fill data gaps for the registered substance using 1-decene dimer, hydrogenated and 1-decene dimer with dodecene, hydrogenated substances. These substances are all hydrogenated poly alpha olefins, i.e., branched saturated paraffins or alkanes produced by oligomerization of 1-octene, 1-decene, and/or 1-dodecene. As described in the read-across justification appended to the CSR, these substances (being branched saturated alkanes) are similar in molecular structure, physicochemical properties, use, and manufacturing processes. Especially relevant to aquatic toxicity are the comparable water solubilities (i.e., very poorly water soluble, < 0.001 mg/L or < 1 ppb) and partition coefficients (log Kow >10). Based on these unifying considerations, the slight difference in carbon number among these analogues is not expected to impact aquatic toxicity. Therefore, it is scientifically reasonable to predict the ecotoxicological properties for the registered substance from the properties determined for the read-across analogues. These substances are related branched alkanes having analogous or homologous molecular structure and very similar inherent physico-chemical properties and are thus expected to exhibit similar toxicological effects.

 

The nature of the read-across approach utilized here is aligned with the “analogue approach” as described in section R.6.2.3 of the ECHA document ‘Guidance on Information requirements and chemical safety assessment Chapter R.6: QSARS and grouping of chemicals’ (ECHA, 2008e). The “analog” similarity among molecular structure and molecular weight which provides the basis for the read-across justification is scientifically founded and therefore adequately clarifies why the properties of the registered substance may be predicted from the properties of the read-across substance(s) and more specifically, why the data submitted for 1-decene, hydrogenated (C20) and 1-decene dimer with dodecene, hydrogenated (C22) are appropriate for the purposes of read-across assessment of the registered substance which contains similar molecules with carbon numbers in the ranges of 18-24 carbon atoms (with at least 85% C20 and C22 components). In addition, these two substances are main C20-C22 constituents in the registered substance.