ABSTRACT
Environmental tobacco smoke [ETS] is one of the most common indoor pollutants to which many children are exposed. The present work was carried out to investigate the his-ological changes of rat tracheal epithelium after postnatal exposure to cigarette smoke. Fifteen newborn albino rats were daily exposed to side-stream cigarette smoke [10 cigarettes a day, 6 days a week] for 12 weeks. From the trachea, paraffin sections were prepared and stained with Haematoxylin and eosin [H and E] stain and alcian blue-periodic acid-Schiff's stain [AB/PAS]. Toluidine blue stained semithin sections were also prepared and examined by light microscope. Ultrathin sections were processed for electron microscopic [EM] examination. In H and E stained sections the tracheal mucosa of the experimental animals showed erosion in the epithilium, oedema, and heavy mono-nuclear cellular infiltrate in the corium which resulted in polyp formation and decreased number of ciliated cells. Preneoplastic variants in the form of squamous metaplasia and dysplasia were also seen. AB/PAS stained sections revealed progressive increase in the number of goblet cells. Semithin sections showed increased number of globule leucocytes, basal cell hyperplasia and dysplasia. Electron microscope revealed swollen cilia, intracytoplasrmic cilia and loss of some basal bodies. Goblet cells were packed with numerous confluent mucus granules. Moreover, degenerated and apoptotic cells were also observed Therefore, it is strongly recommended to protect children from exposure to ETS and to warn parents about the hazards of continuous exposure of their children to cigarette smoke