Recovery from Welding-Fume-Exposure-Induced Lung Fibrosis and Pulmonary Function Changes in Sprague Dawley Rats

Abstract

Welder's pneumoconiosis has generally been determined as benign based on the absence of pulmonary function abnormalities in welders with marked radiographic abnormalities. Yet, there have also been several reports on welders with respiratory symptoms, indicating lung function impairment, X-ray abnormalities, and extensive fibrosis. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during a 60-day welding-fume-inhalation exposure period to elucidate the process of fibrosis. The rats were exposed to manual metal-arc stainless-steel welding fumes (MMA-SS) with total suspended particulate concentrations of 64.8 +/- 0.9 (low dose) and 107.8 +/- 2.6 mg/m3 (high dose) for 2 h per day in an inhalation chamber for 60 days. Animals were sacrificed after the initial 2-h exposure and after 15, 30, and 60 days, and the pulmonary function was also measured every week after the daily exposure. Elevated cellular differential counts were also measured in the acellular bronchoalveolar lavage fluid of the rats exposed to the MMA-SS fumes for 60 days. Among the pulmonary function test parameters, only the tidal volume showed a statistically significant and dose-dependent decrease after 35 to 60 days of MMA-SS welding-fume exposure. When the rats exposed to the welding fumes were left for 60 days to recover their lung function and cellular differentiation, recovery was observed in both the high and low-dose rats exposed up to 30 days, resulting in the disappearance of inflammatory cells and restoration of the tidal volume. The rats exposed for 60 days at the low dose also recovered from the inflammation and tidal volume loss, yet the rats exposed for 60 days at the high dose did not fully recover even after a 60-day recovery period. Therefore, when taken together, the results of the current study suggest that a decrease in the tidal volume could be used as an early indicator of pulmonary fibrosis induced by welding-fume exposure in Sprague Dawley rats, and fibrosis would seem to be preventable if the exposure is short-term and moderate.

Immunotoxicology of arc welding fume: Worker and experimental animal studies

“…Numerous animal studies have examined the toxic effects of welding fumes generated from MMA and GMA welding using different pulmonary exposure routes, such as pharyngeal aspiration, intratracheal instillation (ITI), and inhalation (Taylor et al, 2003;Sung et al, 2004;Yu et al, 2004;. Overall, analysis of the bronchoalveolar lavage fluid (BALF) has shown significant cytotoxicity, air-blood barrier damage, and an inflammatory cytokine response after welding fume exposure via these routes.…”

Recovery from Welding-Fume-Exposure-Induced MRI T1 Signal Intensities after Cessation of Welding-Fume Exposure in Brains of Cynomolgus Monkeys

“…The target concentrations were achieved by varying the flow rates based on adjusting the dampers and measuring TSP concentrations from the sampled filters. The doses were selected based on previous studies conducted with Sprague-Dawley rats, where no distinguishable lung fibrosis was detected after 90 days of welding-fume exposure (Yu et al, 2001(Yu et al, , 2003bSung et al, 2004). More than 90% of the fume particles had aerodynamic diameters of less than 1 µm, and 50% of the diameters were between 0.65 and 0.43 µm .…”

Look closer to welders’ lung

“…Welders may have less noticeable radiological findings than other pneumoconiosis (4,5). In pulmonary radiology, there may be radiographical findings ranging from small indistinct millimetric nodules to groundglass opacites (5,6).…”

“…Siderosis develops by deposition of iron oxide in alveolar macrophages and interstitium which result in prolonged exposure to welding fumes (2,4). Respiratory complaints such as chronic cough, dyspnoea, secretions increase in welders (3).…”