Respiratory tract responses in male rats following subchronic acrolein inhalation

The goal of this study was to characterize the respiratory tract toxicity of acrolein, including nasal and pulmonary effects, in adult male F344 rats. Animals underwent whole-body exposure to 0, 0.02, 0.06, 0.2, 0.6, or 1.8 ppm acrolein for 6 hr/day, five days/week for up to 65 exposure days (13 exposure weeks). Respiratory tract histopathology was evaluated after 4, 14, 30, and 65 exposure days, as well as 60 days after the end of the 13 week exposure. Acrolein exposure was associated with reduced body weight gain. Rats exposed to >= 0.06 ppm acrolein had depressed terminal body weights when compared with air-exposed controls. Histologic evaluation of the nasal cavity showed olfactory epithelial inflammation and olfactory neuronal loss (ONL) following exposure to 1.8 ppm acrolein. Moderately severe ONL in the dorsal meatus and ethmoid turbinates occurred within four days while septal involvement developed with ongoing exposure. A rostral-caudal gradient in lesion severity was noted, with the anterior portion of the nasal cavity being more severely affected. Acrolein exposure was associated with inflammation, hyperplasia, and squamous metaplasia of the respiratory epithelium. The lateral wall was amongst the most sensitive locations for these responses and increased respiratory epithelial cell proliferation occurred at this site following 4 to 30 days of exposure to >= 0.6 ppm acrolein. The NOAEL for nasal pathology seen in this study was 0.2 ppm acrolein.