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Environmental fate & pathways

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Diisotridecyl adipate: The log BCF of diisotridecyl adipate (log Pow = 13.03) was estimated to be 1.17 (BCF 14.8) using the program US EPA EPI Suite v4.00. In addition, a log BAF (upper trophic) of -0.008 (BAF = 0.982) was calculated using the method of Arnot-Gobas.

Diisotridecyl sebacate: The BCF was calculated 3.162 L/kg ww (log BCF = 0.5). In addition, a BAF was estimated to 0.935 (log BAF -0.029 - upper trophic).The low BCF/BAF values indicate a low potential of diisotridecyl adipate and diisotridecyl sebacate for bioaccumulation in aquatic organisms and therefore for the test substance Reaction product of adipic acid and sebacic acid and isotridecan-1-ol. The BCF of 14.83 is something like worst case for the components.

The BCF base-line model estimates the log BCF for the diisotridecyl adipate at 0.85 (BCF = 7.08) indicating low potential for bioaccumulation.The maximum log BCF value was calculated to be 1.39 (BCF = 24.55) . Mitigating factors like metabolism, molecule size and the water solubility were considered by the model.

 

Besides the low water solubility also metabolism and the molecular size reduce the log BCF as estimated by the model. Water solubility and molecular size are also discussed within the literature whether certain threshold values are suitable as cut-off criteria for indication of limited bioaccumulation. Regarding molecular size, the PBT working group on hazardous substances discussed a maximum diameter of > 17.4 Å (Comber et al., 2006). The mean maximum diameter of the test item is determined to be 25.75 Å with the lowest maximum diameter calculated for the 30 energetically preferred 3D structures of the test item being > 17.4 Å (= 18.16 Å).

The potential for accumulation of the read-across substance Bis(2 -ethylhexyl)adipate (DEHA) in aquatic organisms was examined (Felder et al., 1986) in a bioconcentration test using bluegill sunfish (Lepomis macrochirus).The test used a flow through system that maintained the concentration of DEHA at about 250 μg/L using 14C-labeled DEHA.

A steady state concentration of DEHA in the whole fish was attained by day 7. A whole fish bioconcentration factor (BCF) of 27 was reported at day 35. Daily BCFs of 3.2 to 46, 1.3 to 19, and 4.1 to 66 were reported for whole fish, fillet, and viscera samples, respectively. Following exposure to clean water, a depuration rate for DEHA of 0.26/day (t1/2 = 2.7 days) was determined.

DEHA is apparently rapidly and extensively excreted from the fish.

Takahashi (Takahashi et al., 1981) fed radio-labeled Bis(2 -ethylhexyl)adipate (DEHA) to rats and found no evidence of accumulation in any organs or tissues. After 96 hours, less than 0.14% of the administered radioactivity was found in any organ or tissue. From the results, it can be concluded that the elimination of radioactivity from tissues and organs is very rapid and there is no specific organ affinity under the experimental conditions. There was no evidence of the accumulation of radioactivity in any organs or tissues.

Reaction product of adipic acid and sebacic acid and isotridecan-1 -ol is not expected to exhibit a significant bioaccumulation potential. The low water solubility, its molecular size and metabolism further decrease the bioaccumulation potential, which is already considered to be low based on its high log Pow value. Additionally the results on the bioconcentration studies in fish (water) and rats (feeding-study) on the read-across substance DEHA support this assumption.