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Environmental fate & pathways

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The environmental fate of ethylbenzene will be determined by biotic and abiotic degradation processes.

 

Abiotic degradation

Hydrolysis: Evaluation of structure of ethylbenzene shows that it is not expected to hydrolyze appreciably in the environment on the basis of a lack of hydrolysable functional groups.

 

Phototransformation in air: half life of 1.8 days is estimated for reaction of ethylbenzene with hydroxyl radicals in the atmosphere at 25oC [AOPWIN Program, v.1.92]. Overall QSARs estimated half-life for degradation of ethylbenzene in air based upon AOPWIN Model is 36.14 hours.

 

Biodegradation:

Ethylbenzene is a volatile substance which is difficult to test for biodegradation in the experimental systems. The QSAR models predict timeframe within days-weeks for primary biodegradation of ethylbenzene and weeks for its ultimate degradation.

 

QSARs estimated half-lives for biodegradation of ethylbenzene in water and sediment based upon BIOWIN Ultimate Biodegradation are 360 hours (15 days) and 3240 hours (135 days), respectively. Whereas the half-lives of ethylbenzene for volatilization from water are estimated as 0.05 days (for a river) to 4.11days (for a lake) using EPI Suite software.

 

Environmental distribution:

There are no experimental data on environmental distribution of ethylbenzene. QSAR modeling predicts that ethylbenzene will volatize rapidly from surface water with TD50 = 0.05 days (river) and 4.11 days (lake).

 

The low value for soil organic carbon-water partition coefficient (logKoc <3) suggests that ethylbenzene will not adsorb onto soil and sediment and, therefore, together with its high volatility, will not persist in these environmental media.

 

The data on environmental distribution of ethylbenzene obtained from the level III fugacity model suggest that ethylbenzene will not persist in the environment and depending on various emission scenarios, approx. 70% of ethylbenzene will be degraded by both biotic and abiotic mechanisms and approx. 30% will be physically removed (advected) from the environment.

 

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). Moreover, in the GHS classification system the cut-off value of log Kow for bioaccumulation is 4. The estimated log Kow for ethylbenzene is 3.

 

Generally, a BCF in fish of ≥ 500 is indicative of the potential to bioconcentrate for classification purposes in accordance with CLP/GHS criteria. The estimated BCF/BAF values of ethylbenzene in fish (55 -73 L/ kg wet-wt) are well below the cut-off value of 500 for bioconcentration/ bioaccumulation potential in aquatic organisms. Therefore, ethylbenzene is not likely to bioaccumulate in aquatic organisms.

 

Terrestrial bioaccumulation:

By applying the Tier 1 assessment and, in particular, taken into account the structure of ethylbenzene (i. e. a non-ionised organic substance), its physico-chemical properties (i. e. log Kow <4) and environmental fate data suggesting that this chemical will not adsorb to soil particles (logKoc <3) and will likely to volatize from soil, it is considered that the substance is unlikely to be significantly bioaccumulative.