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It is generally assumed that non-ionised organic substances with a log Kow below 3 are not significantly bioaccumulative (refer Section R7c of the ECHA Guidance on information requirements).Penta-1,3-dienehas an estimated log Kow of 2.44 (EPI Suite (v.4.00) software).

The Bioconcentration Factor (BCF), Bioaccumulation factor (BAF) as well as Biotransformation Rate in fish were estimated by the BCFBAF software using the Arnot-Gobas method. This method model estimates steady-state BCF (L/kg) and BAF (L/kg) values for non-ionic organic chemicals in three general trophic levels of fish (i. e. lower, middle and upper) in temperate environments (default temperature is 10oC).

The estimated log Kow forpenta-1,3-dieneis 2.44 which is below the cut-off value of 3 for bioaccumulation. Moreover, in the GHS classification system the cut-off value of log Kow for bioaccumulation is 4.

Biotransformation Half-Life (normalized to 10 g fish at 15oC) of 0.65 days was estimated forpenta-1,3-dienein fish.

In addition, estimated BCF/BAF values ofpenta-1,3-dienein fish (about 21 L/ kg wet-wt) are well below the cut-off value of 500 for bioconcentration potential in aquatic organisms.

Generally, a BCF in fish of ≥ 500 is indicative of the potential to bioconcentrate for classification purposes in accordance with CLP/GHS criteria. The BCF/BAF values estimated forpenta-1,3-dieneare well below the cut-off values for bioaccumulation. Therefore,penta-1,3-dieneis not likely to bioaccumulate in aquatic organisms.

The following information is taken into account for the hazard / risk / bioaccumulation assessment:

Log BCF (regression-based estimate)= 1.28 ; BCF = 18.9 L/kg wet-wt;

Biotransformation Half-Life (normalized to 10 g fish at 15 deg C) =0.648 days;

Log BAF (Arnot-Gobas, upper trophic)=1.42; BAF =26.6 L/kg wet-wt;

Log BAF(Arnot-Gobas, mid trophic) =1.27; BAF =18.6 L/kg wet-wt;

Log BAF (Arnot-Gobas, lower trophic)=1.22; BAF=16.58 L/kg wet-wt