The effect of exposure to SO2 on the respiratory system of power-station workers

Sulfur dioxide (SO2) is generally recognized as a respiratory irritant, but its effects if any at low levels of exposure are uncertain. We studied 38 power station technicians exposed to 0.8 ppm (parts per million) 8-h weighted levels of sulfur dioxide, and compared them to workers performing similar tasks without such exposure. Those exposed complained 5.8 times more frequently of cough (95% CI =1.8-20.6, P < 0.001), and also had significantly more sputum production. There was also a trend for increasing prevalence of dyspnea. On the other hand there was no decrease in pulmonary function test values. In the eight exposed subjects who complained of dyspnea, there was a significant decrease in pulmonary flow values. We conclude that power station workers exposed to low levels of SO2 have increased respiratory symptoms, and deserve compensation if their symptoms become chronic. The pulmonary function tests were not different from the control subjects, but there may be a small group who are prone to long-term morbidity. Additional studies are warranted to confirm our findings, and to define immediate and long-term morbidity due to low exposure to SO2.