Chronic effects of welding exposure on pulmonary function tests and respiratory symptoms Objectives: The respiratory effects of exposure to welding fumes have been investigated in numerous studies; but results of these studies have not been consistent. The aim of the present study was to investigate the respiratory effects of welding exposure in a large group of manual arc welders exposed primarily to mild steel welding processes in confined spaces without respiratory protection.

Methods: Respiratory symptoms and lung functions were studied in 110 welders and 55 controls. The welder group comprised all the welders in the workshops of two companies in a single municipality. Welders exposed to any other chemicals known to be injurious to the lung were excluded. Clerks from the same companies were selected as controls. These were 55 men of similar ages and socioeconomic situation, but who had no occupational dust or gas exposure.
The welders and controls were of similar average age and height; smoking habits of the groups were similar. Chest x ray films were taken to exclude people with radiological abnormalities that may influence pulmonary function tests. Welders were grouped according to smoking habits and duration of employment ( 20 years).

Results: Respiratory symptoms and chronic bronchitis were more prevalent in welders (P < 0.05). Welders who were smokers showed a higher frequency of chronic bronchitis than controls who smoked (P < 0.05). The difference in occurrence of chronic bronchitis between welders who smoked and welders who were non-smokers or ex-smokers was not statistically significant.
In addition to chronic bronchitis, several measurements of lung health were recorded for each person in the samples. Compared with the controls, forced vital capacity (FVC), forced expiratory (FEV1), peak expiratory flow (PEF), and maximum midexpiratory flow (MMEF) were significantly lower in welders (mean (standard deviations) values of FVC for welders and controls were 86.06 (25.74) and 96.40 (13.03); and values for FEV1 were 87.54 (13.70) and 95.36 (12.40) respectively; P < 0.01).
There was no significant difference in pulmonary function tests between welders who were non-smokers and controls who were non-smokers; whereas FVC, FEV1, PEF, and MMEF were significantly lower in welders who smoked than controls who smoked (P < 0.01). There were no statistically significant differences in pulmonary function tests and occurrence of chronic bronchitis between welders with More or Less than 20 years at work.

5) Hypothesis tests from the results section say that there are associations between welding with bronchitis and welding with forced vital capacity. Which variable (bronchitis or FVC) do we have stronger evidence of an association?

6) What type of test did the researchers conduct to test if there was a difference in FVC between welders and controls who were non-smokers? What is the correct null hypothesis?

7) A graphical representation of the results accompanied the comparison of lung health between welders and non-welders was included in the research paper. What type of graph did they make?

8) Does there appear to be an association between time at the job and pulmonary function for welders? How did you reach your conclusion?