Biochemical and Histopathological Effects of Acute Exposure to Vinyl Acetate Monomer Vapour in Wistar Rats

Background: Vinyl acetate monomer is a commodity chemical widely used in the manufacturing of various products. The chemical is hazardous and exposure to it may occur in both occupational and non-occupational settings. The aim of this study was to characterize the effects of short-term exposure to Vinyl Acetate Monomer (VAM) vapour on the liver and lungs of Wistar rats. Methods: Mice weighing 25-30g were used to determine the acute lethal dose, while Wistar rats weighing 120-140g were randomly assigned to a control group and two experimental groups, which were exposed daily to VAM vapour for 2 or 4 hours. On the 5th day, rats were sacrificed, the blood was collected for biochemical analysis while liver and lungs were examined for histological alterations. Results: The acute lethal dose of VAM vapour was estimated to be 173.21 mg/kg body weight. A significant decline in total protein (6.725±0.10 g/dl; p<0.05) and increases in alanine aminotransferase (ALT; 33±1.47 u/l), aspartate aminotransferase (AST; 44±1.08 u/l), alkaline phosphatase (ALP u/l; 76.42±1.43), urea (22.89±0.93 mg/l), bilirubin (0.84±0.03 mg/dl) and creatinine (1.04±0.07 mg/dl) occurred in the experimental rats compared to the controls. Portal inflammation, fibrosis, and hepatitis were observed in the liver, while collapsed air spaces, thickened alveolar walls and haemorrhage were demonstrated in the lungs of the experimental rats. The extent of these lesions increased with rising exposure time to VAM vapour. Conclusion: This study demonstrated that VAM liquid was moderately toxic, while short-term exposure to VAM vapour was injurious to the lungs and liver of Wistar rats.