Degeneration and regeneration of respiratory mucosa of rats after exposure to styrene.

The recovery process of pathological changes in the respiratory mucosa following exposure to styrene were experimentally studied to improve the understanding of the respiratory toxicity of styrene. Thirty male SD rats were exposed to 150 ppm or 1000 ppm of styrene for 4 h a day over 3 weeks (5 days a week). They were killed for examination at 1 day or 12 weeks after completion of the exposure sequence. Bilateral mucosal samples from the nasal septum and the trachea of the animals were examined for ciliary activity and subjected to electron microscopy. Complete functional and morphological recovery of the nasal and tracheal mucosa was observed at the 12th week post-exposure to 150 ppm of styrene. After exposure to 1000 ppm of styrene, almost normal function and morphology of the tracheal mucosa was found at the 12th week post-exposure, but the nasal mucosa continued to show decreased ciliary activity and an affected morphology.