Physiological modeling of the relative contributions of styrene-7,8-oxide derived from direct inhalation and from styrene metabolism to the systemic dose in humans

Workers in the reinforced plastics industry are exposed to large quantities of styrene and to small amounts of the carcinogen, styrene-7,8-oxide (SO), in air. Since SO is also the primary metabolite of styrene, we modified a published physiologically based pharmacokinetic (PBPK) model to investigate...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Toxicological sciences 2001-12, Vol.64 (2), p.151-161
Hauptverfasser: TORNERO-VELEZ, Rogelio, RAPPAPORT, Stephen M
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:Workers in the reinforced plastics industry are exposed to large quantities of styrene and to small amounts of the carcinogen, styrene-7,8-oxide (SO), in air. Since SO is also the primary metabolite of styrene, we modified a published physiologically based pharmacokinetic (PBPK) model to investigate the relative contributions of inhaled SO and metabolically derived SO to the systemic levels of SO in humans. The model was tested against air and blood measurements of styrene and SO from 252 reinforced plastics workers. Results suggest that the highly efficient first-pass hydrolysis of SO via epoxide hydrolase in the liver greatly reduces the systemic availability of SO formed in situ from styrene. In contrast, airborne SO, absorbed via inhalation, is distributed to the systemic circulation, thereby avoiding such privileged-access metabolism. The best fit to the model was obtained when the relative systemic availability (the ratio of metabolic SO to absorbed SO per unit exposure) equaled 2.75 x 10(-4), indicating that absorbed SO contributed 3640 times more SO to the blood than an equivalent amount of inhaled styrene. Since the ratio of airborne styrene to SO rarely exceeds 1500 in the reinforced plastics industry, this indicates that inhalation of SO presents a greater hazard of cytogenetic damage than inhalation of styrene. We conclude that future studies should assess exposures to airborne SO as well as styrene.
ISSN:1096-6080
1096-0929
1096-0929
DOI:10.1093/toxsci/64.2.151