Histopathological Effects of Soldering Fumes on Respiratory Tract Epithelium in Rat

Fumes generating during soldering process are a group of metal vapors and gases such as tin, lead and formaldehyde which are one of the main reasons for lung diseases in solders. Respiratory epithelium in trachea is the first biological barrier which responds to these fumes. The aim of this study was to identify the quantitative effects of these fumes in respiratory epithelium of rats. A total number of 48 adult male Sprague Dawley rats were randomly divided into experimental (n=30) and control (n=18) groups. Each group was subdivided into 2, 4 and 6-week subgroups based on the time of tissue sampling. After adaptation to standard situation in animal house, rats in experimental group were exposed to soldering fumes for 1 hour in exposure chamber (0.83m3). Air sampling from the exposure chamber was done daily with two different methods. According to the schedule, tissue specimens were taken from trachea in deep anesthesia. After processing, all samples were sectioned and stained and the thickness of the respiratory epithelium of trachea was measured under light microscopy. There was a significant difference between all of control and experimental subgroups (p<0.000). There was also a significant difference between experimental groups of 6-week subgroup with 2-week subgroup (p<0.001). The amount of the formaldehyde, tin (Sn) and lead (Pb) in gas exposure chamber was 0.193 mg/m3, 0.35 mg/m3 and 3 mg/m3 respectively. It seems that the respiratory epithelium of the trachea responds to the soldering fumes and the changes in epithelial thickness are time dependent.