RESUMO
Background: Zinc oxide nanoparticles (ZnO-NPs) are frequently used in many fields, including food industry fortheir antimicrobial activity. Acute exposure to high doses of such particles was found to be toxic to many organs.However, the lung toxicity resulting from chronic exposure to oral doses of ZnO-NPs was not adequately assessedbefore.Aim of the work: to detect the anatomical and histopathological effects of chronic exposure to ingested ZnO-NPson the lung of normal adult male albino rat.Material and methods: It was carried out on 30 adult male Swiss albino rats with an average weight of 150-200gm. They were divided into two groups: Group I: 10 rats serving as control group; Group II: 20 rats serving asexperimental groups, divided into 2 subgroups (a&b) receiving oral ingestion by orogastric tube of a single dailydose (125mg/ kg) of average 20 nm sized ZnO-NPs for different durations: Group IIa (n=10): for 120 days; GroupIIb (n=10): for 180 days. Histopathology and immunohistochemistry of the lungs in the three groups was performedto detect the possible effect of such exposure.Results: Oral administration of ZnO-NPs induced lung damage manifested by congested blood vessels, interstitialinflammation, infiltration with macrophages& lymphocytes, supurative granuloma, thickened interalveolarsepta. These changes were more evident with longer exposure for 180 days (P < 0.5). This substantial damage tothe lungs is caused by oxidative stress and chronic inflammation.Conclusion: Caution should be considered when using these particles in food packaging and food additives, andfor those who are in close contact with these particles especially in factories.