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Description of key information

There are no toxicokinetic data on low benzene naphtha streams, however the marker substance toluene is absorbed rapidly via inhalation (approximately 50% uptake) and ingestion (100% of dose) but shows only limited uptake after skin contact (3.6%). Once absorbed, around 80% of absorbed toluene is metabolised in the liver by hydroxylation and conjugation and excreted in urine; around 20% is eliminated via expired air. A calculated BCF of 99-5790 indicates some potential for these streams to bioaccumulate.

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
100
Absorption rate - dermal (%):
3.6
Absorption rate - inhalation (%):
50

Additional information

No experimental information is available on the toxicokinetic behaviour of the streams comprising this category, however equivalent information is available for the component substances that are present. The marker substance toluene is absorbed rapidly via inhalation (approximately 50% uptake). Dermal absorption of liquid toluene, predicted using a two stage model, gave a dermal absorption value of approximately 3.6% of the applied dose. Oral uptake is estimated to be complete (100% of the dose). Once absorbed, toluene is distributed systemically with the amount present in body tissues reflecting the tissue/blood partition coefficient, the duration and level of exposure, and the rate of elimination. Around 80% of an absorbed dose of toluene is metabolised in the liver by the P450 system, mainly via benzyl alcohol and benzaldehyde to benzoic acid. Benzoic acid is conjugated with glycine and excreted in the urine as hippuric acid. Elimination of unchanged toluene is rapid, with around 20% of an absorbed dose eliminated via expired air. Within a few hours after termination of exposure, blood and alveolar air contain very little toluene, with most toluene eliminated from fat after 12 hours.