Effect of formaldehyde inhalation on rabbit nasal mucosa: a light microscopic study—an animal model for inhalational irritants on nasal mucosa

Background Formaldehyde is associated with many adverse health effects and is classified as a human carcinogen. Formaldehyde is highly water-soluble and readily absorbed and metabolized by the respiratory mucosa upon inhalation. The histopathological effects of formaldehyde on the nasal mucosa and olfactory nerves in adult New Zealand white rabbits were studied to validate this animal model of inhalational irritants. Results Compared to control group 1 (exposed to air), groups 2 and 3 (exposed to formaldehyde for 90 min and 210 min, respectively) exhibited disrupted nasal tissue, ulcerated epithelial coverings, markedly dilated blood vessels, and increased numbers of inflammatory cells in the lamina propria. The olfactory neuro-epithelium exhibited a reduction in the number of cilia. Many sustentacular cells lost their microvilli. Olfactory nerves exhibited nerve bundle shrinkage within the perineural sheath, leaving an empty space with evidence of edema within the nerve fibers. Conclusion Formaldehyde inhalation has destructive effects on the nasal mucosa and olfactory nerves in adult New Zealand white rabbits. These results validate the use of this animal model to assess the effects of inhalational irritants on the nasal mucosa.