Long-term vibration exposure of humans leads to development of manifest atrophy and structural mosaicism of the bronchial epithelium in the mucosa of the large bronchi (diffuse degeneration of multilamellar cylindrical epithelium, focal hyperplasia, and squamous cell metaplasia). The mucosal subepithelial stroma is characterized by sclerosis, hypoelastosis, and reduction of microvessels. Radioautography confirms the reduction of protein-producing activity of bronchial epitheliocytes and endotheliocytes.