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Environmental fate & pathways

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Aquatic bioaccumulation

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). Styrene has an estimated log Kow of 2.89 (a very close default value used in EPI Suite (v.4.00) software for styrene is log Kow=2.95).

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 for styrene is 2.89 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 0.501 days was estimated for styrene in fish.

In addition, estimated BCF/BAF values of styrene in fish (about 41 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 for styrene are well below the cut-off values for bioaccumulation. Therefore, styrene is not likely to bioaccumulate in aquatic organisms.

Terrestrial bioaccumulation

Tests on terrestrial bioaccumulation are not required to be performed under Annexes VII to X of REACH.

No experimental data on terrestrial bioaccumulation of styrene were located or performed by the registrant. In addition, no QSAR model estimation was performed for terrestrial bioaccumulation.

By applying the Tier 1 assessment and, in particular, taken into account the structure of styrene (i. e. a non-ionised organic substance), its physico-chemical properties (i. e. log Kow <3) and environmental fate data suggesting that this chemical will not adsorb to soil particles (logKoc = 2.56 -2.65) and will likely to volatize from soil, it is considered that the substance is unlikely to be significantly bioaccumulative.