Registration Dossier

Administrative data

Link to relevant study record(s)

Description of key information

There are no toxicokinetic studies of gasoline or naphthas, per se.  However, assessments of gasoline constituents can be used as the basis for understanding the toxicokinetics of gasoline or naphthas as complex substances.

Key value for chemical safety assessment

Additional information

There are no experimental studies of the toxicokinetics of gasoline per se, but there have been numerous toxicokinetic studies of the major gasoline constituents. The principal route of exposure for most individuals is inhalation. It has been shown that absorption of inhaled constituents increases with increasing molecular weight, with n-paraffins being more highly absorbed than iso-paraffins and aromatics being more highly absorbed than the corresponding paraffins. The low molecular weight constituents (butanes and pentanes) are poorly absorbed and predominantly exhaled unchanged. The higher molecular weight constituents are more efficiently absorbed, with metabolism, normally to the corresponding alcohols, and excretion in the urine becoming increasingly important. About 15% of the butanes and pentanes are absorbed with biological half-times measured in minutes. About 25% of the hexanes and 50% of the higher molecular weight constituents are absorbed with biological half-times ranging from approximately 3-12 hours depending on whether the assessment is based on blood or urinary levels.

Dermal contact normally contributes little to overall dose as gasoline constituents in the vapor phase are poorly absorbed percutaneously. Studies with toluene indicate that dermal absorption from vapor is approximately 1% of the amount absorbed by inhalation. When contacted as liquid, gasoline constituents are also poorly absorbed if allowed to evaporate. However, if evaporation is impeded then the fraction absorbed can be substantial. Other toxicokinetic properties of percutaneously absorbed gasoline constituents are similar to material absorbed by inhalation.

Oral ingestion also normally contributes little to overall dose as gasoline is not intended for consumption. However, most of the constituents are well absorbed from the gastrointestinal tract. An assumption of 100% bioavailability of ingested material is reasonable.