Differences in Nasopharyngeal and Lung Histopathology in Wistar Rats (Rattus norvegicus) Given Inhaled Formaldehyde Exposure with Doses of 20, 30, and 40 ppm

Background: Formaldehyde is known as a chemical substance that may induce structural cell changes in several organs, especially the respiratory system. Different concentrations of exposure may result in different degrees of severity in histopathology. Method: Twenty male Wistar rats were divided into 4 groups. Inhalation of 10% formaldehyde exposure in 6 hours per day over 16 weeks was done. Nasopharyngeal and lung tissues were taken with hematoxylin-eosin (H&E) staining to see histopathology structural changes and degree of severity. Bivariate analysis was conducted to find the correlation coefficient. Results: This experimental study found that severe dysplasia is correlated with long exposure. A strong correlation is found between concentrations and dysplasia (r=0.682), and a moderate correlation between duration of exposure and dysplasia (r=0.488).Discussion: Dysplasia of nasopharyngeal and lung tissue are in line with exposure of formaldehyde in rats. Formaldehyde exposure with 10 ppm and 15 ppm may lead to structural cell changes such as vacuolar degeneration, cell necrosis, epithelial exfoliation, and erosion in nasal passage. Also, longer exposure increases the severity of dysplasia. Squamous metaplasia was found in 20 ppm of formaldehyde over 2 weeks of exposure, in the epithelial respiratory system. Conclusion: The severity of dysplasia in rats is in line with the duration and concentrations of formaldehyde exposure. Long exposure will increase the severity of dysplasia and, similarly, high concentration of formaldehyde exposure increases the severity of dysplasia.