Welding fumes as a cause of impaired lung function in shipyard workers
Welders and caulker/burners are usually exposed to heavy clouds of fumes. These fumes contain some gases and particulates which are potentially harmful. There have been several surveys of the health of welders since 1936. These studies demonstrated an association between exposure to fumes and respiratory symptoms. However, no long term effect of fumes on respiratory function has been established. The gases and particulates in the fumes from welding and caulking/burning are very small in size and on this account are capable of reaching the small airways in the periphery of the lung. If welding fumes are harmful to the lung small airway dysfunction should be present in the younger workers. In view of this, in the present study relatively young men were examined and tests specific to small airway function were used. The subjects for this study were male Caucasian workers aged 18 - 47 years, mean age 31.5 years. The target sample comprised 181 welders and 151 caulker/burners and the control sample comprised 181 other tradesmen. The two samples were selected from the same yard. Anthropometry, respiratory symptom and occupational questionnaires, cough frequency questions, forced spirometry, single breath nitrogen test, transfer factor, and an exercise test were performed. The results were submitted to multiple regression analysis. The target workers were compared with the control subjects. Comparisons were also made within the groups of welders and caulker/burners separately. A subsample of the whole selected subjects (age 20 - 25 years) was examined separately to investigate the early effects of fumes on the lung of exposed young workers. In the whole population, compared with the controls, the welders and caulker/burners were found to have significantly higher prevalence of wheeze symptom, and fume exposure interacted with age to increase breathlessness on exertion in the older subjects. In the very young workers (age 20- 25 years) chronic cough and phlegm (chronic bronchitis, MRC) was significantly higher among the target workers compared with the controls. In the group of welders smoking interacted with fumes to increase wheeze in the workers who smoked while increased fume exposure in the older subjects was associated with increased breathlessness on exertion. In the whole population the mean values of closing volume (CV%) and closing capacity (CC%) were significantly higher in the target workers compared with the controls. This effect was independent of age and smoking which were also important. In the subsample of the very young workers similar effects were found, and in addition the mean value of the residual volume (RV%) in the target group was significantly higher than that in the control group. In the whole population fume exposure enhanced the deterioration with age in forced expiratory volume (FEV1) and forced vital capacity (FVC) significantly more in the target workers than in the control subjects. These indices were not affected by exposure in the very young workers. Amongst the group of welders, increased levels of exposure to fumes (duration and intensity) enhanced the deterioration with age in CV%, CC%, breathlessness on exertion and Tlco. High exposure was also associated with decreased Kco in the workers who smoked. Amongst the caulker/burners, increased levels of exposure to fumes enhanced the deterioration with age in CV%, CC%, slope of phase III (SLIII), nitrogen difference index (N2 Diff) and RV%. The findings of the present study are evidence that high levels of fumes from welding and burning or other factors related to these trades, cause long term impairment of lung function of shipyard welders and caulker/burners.