Nasal Mucosal Heavy Metal Accumulation, Olfactory Dysfunction, and Histopathological Changes: A Prospective Clinical...

Background/Objectives: Heavy metals are environmental hazards that are recognized as neurotoxic agents that may impair olfactory pathways in susceptible individuals. This study aimed to determine the concentrations of cadmium (Cd), arsenic (As), lead (Pb), chromium (Cr), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn), iron (Fe), and mercury (Hg) in the nasal mucosa and secretions of patients diagnosed with nasal septal deviation, nasal polyposis, or chronic rhinosinusitis, and to investigate their associations with olfactory function, nasal airflow, and pathohistological changes in the nasal mucosa. Methods: This prospective study included 97 adult patients who underwent nasal surgery. We used the Smell Diskettes Olfaction Test to assess olfactory function and rhinomanometry to evaluate nasal airflow resistance. Nasal mucosal tissue samples were collected intraoperatively. Heavy metal concentrations were analyzed using inductively coupled plasma mass spectrometry and atomic absorption spectrometry. Results: Preoperative olfactometry scores in patients with olfactory dysfunction differed to those in patients without olfactory dysfunction (3.4 ± 1.3 vs. 4.1 ± 1.2). Inferential analysis of heavy metals and olfactometry revealed that Cr, Fe, and Pb concentrations were negatively associated with olfactory performance before exposure (Cr: β = -0.12, p = 0.018; Fe: β = -0.08, p = 0.009; Pb: β = -0.10, p = 0.048). Rhinomanometry parameters showed positive associations with olfactory function, independently of age, sex, and groups of patients with or without olfactory dysfunction (R1: β = 0.45, p < 0.001; R2: β = 0.30, p = 0.003). Stepwise regression identified Fe, Pb, and Cr as the strongest predictors of olfactory dysfunction. The adverse effects of Fe and Pb exposure were significantly amplified with age. MANOVA revealed significant differences in heavy metal concentrations across pathohistological categories (Wilks' Lambda = 0.038, p < 0.001). Carcinoma tissue exhibited significantly higher Cr concentrations, whereas precancerous lesions exhibited increased Cd concentrations. Conclusions: Cr, Fe, and Pb accumulation in nasal mucosa secretion is significantly associated with impaired olfactory function and pathohistological changes. Prolonged exposure to environmental heavy metals may affect olfactory function in the elderly population.