Formaldehyde Exposure Induces Bronchial, Haematological, and Biochemical Alterations in Wistar Rats

Abstract

Background: Formaldehyde fumes are hazardous environmental pollutants with established respiratory toxicity; however, their effects on bronchial histoarchitecture alongside systemic haematological and biochemical changes remain incompletely characterized.

Methods: This randomized controlled experimental study involved twenty-four adult Wistar rats of both sexes (248–260 g), assigned into four groups (n = 6). Group A served as control, while Groups B, C, and D were exposed to increasing concentrations of formaldehyde fumes generated from 10ml, 20ml, and 40ml of 40% formaldehyde, respectively, for 28 days. Bronchial histology, haematological indices, and biochemical parameters, including serum bicarbonate, urea, and creatinine, were assessed. Data were analyzed using one-way ANOVA at p < 0.05.

Results: Formaldehyde exposure produced concentration-dependent alterations across all evaluated parameters. Serum bicarbonate levels showed a significant, dose-dependent decline in formaldehyde-exposed groups compared with the control group (A) (P < 0.05), indicating disturbance in acid–base balance. In contrast, serum urea and creatinine levels increased significantly in exposed groups relative to controls (P < 0.05), reflecting progressive impairment of renal function with increasing formaldehyde exposure.

Haematological analysis revealed significant reductions in lymphocytes, basophils, red blood cell indices, haemoglobin, and haematocrit, alongside elevated reticulocyte counts (p<0.05 each), suggesting anaemia and immune suppression. Histological examination of bronchial tissues demonstrated dose-dependent pathological changes, including mucosal ulceration, inflammatory cell infiltration, activated lymphoid follicles, and luminal haemorrhage, consistent with bronchitis.

Conclusion: Sub-chronic inhalation of formaldehyde fumes induces dose-dependent bronchial histopathology, haematological dysregulation, electrolyte imbalance, and renal dysfunction in Wistar rats. These findings underscore significant occupational health risks and highlight the need for stringent exposure control measures.