1-Dodecene, mixed with 1-decene and 1-octene, dimers, hydrogenated

Short-term toxicity to aquatic invertebrates

Description of key information

Data directly assessing the short-term toxicity in aquatic invertebrates for the registered substance. are not available.  However, there are read-across acute toxicity data in invertebrates for two primary components, namely, 1-decene dimer hydrogenated and 1-decene dimer with dodecene, hydrogenated as well as a structurally related C24 PAO surrogate material to help assess the registered substance, reaction products of 1-decene, 1-dodecene and 1-octene, hydrogenated.  
Using the “analog” read-across approach as discussed above, the read-across results of the mysid or Daphnia magna toxicity studies for the hydrogenated PAO related constituent substances support the assessment that the registered substance is not be expected to cause acute toxicity in aquatic invertebrates at the maximum water solubility limit.  NOEL > 1000 mg/L (loading rates) were reported for the two read-across PAO read-across surrogates (C20-C24).  However, the use of NOEL values reported in the table below for risk assessment is inappropriate as these values are not true NOECs as discussed in CSR Section 7.1.1

Additional information

Read-across short-term toxicity studies in aquatic invertebrates (mysids and daphnids) are summarized in the accompanying table. 1-Decene dimer hydrogenated has been shown to cause no mortality inMysidopsis bahiain saltwater even at the highest WSF test concentrations of 5056 mg/L (Mobil Environmental and Health Sciences Laboratory, 1992c). In addition, 1-decene dimer with dodecene, hydrogenated (CAS 151006-58-5) has been evaluated for immobilization in the water flea,Daphnia magna, in freshwater (ABC Laboratories, 1989b). Water soluble fractions (WSF) of this 1-decene dimer with dodecene, hydrogenated material did not produce any toxicity at 9.6 and 19 mg/L nominal loadings. Minimal toxicity (<10% immobilization) was observed at 37, 75 and 150 mg/L WSF. An extrapolated 48-hr EL50 of 230 mg/L WSF (nominal loading) was reported for this material. Hence, 1-decene dimer with dodecene hydrogenated would be considered "not harmful". This hydrogenated C10-C12 PAO material would not be expected to cause significant acute toxicity up to the limit of its water solubility. At higher WSF concentrations, there was the confounding effect of an oily film being formed in the test solutions which led to the potential physical entrapment of the daphnids. However, in relatedDaphnia magnastudies for a similar viscosity and structurally-related PAO surrogate material (i.e., 2.5 cst, 1-dodecene dimer hydrogenated, C24 substance, CAS #151006-61-0) where oil film or droplet formation did not occur and physical entrapment was avoided, no immobilization was observed at the highest WAF nominal loading of 1000 mg/L (presumably at the maximum water solubility limit) (SafePharm Laboratories, 1995 and see table).

The read-across results of the mysid orDaphnia magnatoxicity studies for the hydrogenated PAO related constituent substances support the assessment that the registered substance is not be expected to cause acute toxicity in aquatic invertebrates at the maximum water solubility limit. NOEL > 1000 mg/L (loading rates) were reported for the two read-across PAO read-across surrogates (C20-C24). However, the use of NOEL values reported in the table below for risk assessment is inappropriate as these values are not true NOECs as discussed in CSR Section 7.1.1.

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 and 1-dodecene dimer, hydrogenated. 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 variation 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 (C20-24) and 1-dodecene dimer hydrogenated (C24) 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% or more C20-C24 components).