Pattern of deposition of stainless steel welding fume particles inhaled into the respiratory systems of Sprague-Dawley rats exposed to a novel welding fume generating system

In order to investigate occupational diseases related to welding fume expos ure, such as nasal septum perforation, pneumoconiosis and manganese intoxic ation, we built a welding fume exposure system that included a welding fume generator, exposure chamber and fume collector. The fume concentrations in the exposure chamber were monitored every 15 min during a 2-h exposure. Fu me (mg/m(3)) concentrations of major metals, including Fe, Mn, Cr, and Ni w ere found to be consistently maintained. An acute inhalation toxicity study was conducted by exposing male Sprague-Dawley rats to the welding fumes ge nerated in this apparatus by stainless steel are welding. The rats were exp osed in the inhalation chamber to a welding fume with a concentration of 62 mg/m(3) total suspended particulates for 4 h. Animals were sacrificed at 4 h and at 1, 3, 7, 10, and 14 days after exposure. Histopathological examin ations were conducted on the animals' upper respiratory tracts, including t he nasal pathway and the conducting airway, and on the gas exchange region including the alveolar ducts, alveolar sacs, and alveoli. Diameters of fume particles varied from 0.02 to 0.81 mu m and were distributed log normally, with a mean diameter of 0.1 mu m and geometric standard deviation of 1.42. Rats exposed to the welding fume for 4 h did not show any significant resp iratory system toxicity. The mean particle diameter of 0.1 pm resulted in l ittle adsorption of the welding fume particles in the upper respiratory tra ct. Particle adsorption took place principally in the lower respiratory tra cts, including bronchioles, alveolar ducts, alveolar sacs, and alveoli. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.