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

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The registered substance , i.e., “the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated”, is not persistent (P) or very persistent (vP) based on standard test guidelines.

Justificaton for not PPT / vPvB is discussed below:

The screening criteria for P and vP require a biodegradation half-life of >40 and >60 days, respectively, in freshwater. A study carried out in freshwater with the registered substance under OECD ready biodegradability test guidelines (Mobil Business Resources Corp., 1997) demonstrated that it was biodegraded to >60% in 28 days, based on CO₂evolution. These findings clearly indicate that the registered substance is “readily biodegradable” for complex substances under REACH; see discussion under CSR Section 4.1.2.1.2 (ECHA 2008a).

 

In summary, these findings indicate that the registered substance is not persistent (P) or very persistent (vP) based on initial screening using standardized ready biodegradation test data. Two primary components of the registered substance, namely, 1-decene dimer, hydrogenated CAS No. 68649-11-6 and 1-decene dimer with dodecene, hydrogenated (CAS No. 151006-58-5)] also meet the not P and not vP criteria based on their greater than 60% biodegradation in 28 days.

 

The registered substance is not bioaccumulative (B) or very bioaccumulative (vB) based on calculated bioconcentration factor (BCF) or log BCF values. The very low water solubility and high partition coefficient of the test material makes it impossible to conduct a reliable aqueous BCF study for the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated. Therefore, the Arnot-Gobas BCF model (US EPA EPI-Suite, BCFBAF v3.0) was usedto calculate log BCF values in order to assess the bioaccumulative potential of the registered substance. The calculated log BCF values for the main C20-C22 components ranged from 0.412 to 1.038. The minor C18 and C24 components gave calculated log BCF values of 1.74 and 0.068, respectively.

 

This data support the fact that the BCF for the registration substance is well below the2000 L/kg (or below log BCF 3.30) which is the criterion for not being considered bioaccumulative (B) and is well below the 5000 L/kg (or below log BCF 3.699) which is the criterion for not being considered very bioaccumulative (vB).

 

These findings are consistent with the fact that the registered substance is readily biodegradable and is expected to undergo rapid metabolism in the aquatic and terrestrial environment and organisms, thus limiting bioaccumulation. In addition,a very high log Kow (>10) may be a mitigating factor that limits uptake of the substance across membranes due to bioavailability/membrane permeation. As pointed out in the ECHA PBT Assessment guidance document, Chapter R11.1.3.2 (bioaccumulation assessment, pg 28), “the aquatic BCF of a substance is probably lower than 2000 L/kg if the calculated log Kow is higher than 10” (ECHA 2008b). The registered substance has a calculated log Kow >10 based on its main components and under the above ECHA guidance document would not be considered bioaccumulative or very bioaccumulative.

 

Limitations of BAF Arnot-Gobas model(Registrant’s comments): 

While the BAF Arnot-Gobas model v3.0 is also available in US EPA EPI-Suite BCFBAF program, based on our knowledge and experience, it is not applicable to the registered substance because the BAF model does not accurately predict the bioaccumulative potential of petroleum hydrocarbon compounds such as branched alkanes and aliphatics hydrocarbons that can be metabolized in the gut and thus overestimates bioaccumulation predictions involving dietary exposures. Petroleum substances are not included in the model domain because this model was calibrated on non-metabolizable compounds such as PCBs and other recalcitrant compounds. As a result, petroleum hydrocarbon susceptible to gut biotransformation are not reliably predicted by the BAF model and bioaccumulation is overestimated since the contribution from dietary exposure is exaggerated. Therefore, it is not valid to consider predictions obtained from the current BAF Arnot-Gobas model for assessing the bioaccumulation potential of the registered substancegiven its limited domain of applicability. In contrast, the Arnot-Gobas BCF model does reliably address tissue biotransformation rates for petroleum hydrocarbons and is acceptable for use in estimating the log BCF value for the registered substance as discussed above. The BCF model does not suffer the same limitations as the BAF model because it was trained on a much broader set of chemicals including petroleum hydrocarbons.

 

The reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated are not toxic (T) based on results from chronic aquatic toxicity studies that show no effects at levels equal to or exceeding the maximum water solubility and mammalian toxicity studies that support not classifying the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated as carcinogenic, mutagenic, toxic for reproduction, or assigning classifications of T, R48 or Xn, R48.

Read-across analogue data from 21-day survival and reproduction studies withDaphnia magna(water flea) for structurally similar PAO substances support the assessmentthatthe registered substance would not be expected tocause chronic aquatic toxicity at the maximum concentrations reached under the conditions of the tests. The chronic toxicity of these PAO substances as measured by reproductive success toDaphnia magnawas evaluated using OECD guideline 211. No significant effect was observed at the maximum water solubility limit (as WAF solution) under the conditions of the test for the hydrogenated PAO surrogate materials [Springborn Laboratories (1998); Covance Laboratories (2001)]. These read-across findings indicate that the reaction products of 1-decene, 1-dodecene, and 1-octene, hydrogenated would not be expected to produce chronic toxicity toDaphnia magna. See section 7.1.1 for additional information from aquatic toxicity studies showing no acute or chronic toxicity. Therefore, the registered substance is not classified or labelled for the environment and does not meet the criterion for T based on aquatic toxicity.