INHALED MANUAL METAL ARC AND SHIELDGAS STAINLESS AND MILD STEEL WELDING FUMES IN RAT LUNG

Abstract Rats were exposed to shieldgas stainless steel (MIG/SS), manual metal arc stainless steel (MMA/SS) or mild steel (MMA/MS) welding fumes (50 mg/m 3 ) for four weeks. Inhaled fume particles were studied in lung tissue of animals by light and transmission electron microscopy, and analysed in situ using energy dispersive X-ray microanalysis. The relative X-ray intensities of elements in particles were converted to weight fractions by the Cliff-Lorimer method. Air samples of the same welding fumes were studied by the same methods. Fume particles were seen in alveolar macrophages and epithelial cells mostly in groups or conglomerates which were formed of particles of about 5 to 250 nm in diameter. The composition of the MIG/SS fume and the minor particle type of MMA/SS fume were identical and these particles showed no signs of solubility in tissue. The predominant particle type of MMA/SS fume had, however, lost its most soluble components. In the lungs exposed to MMA/MS welding very few particles were found.