The South Karelia air pollution study: Changes in respiratory health in relation to emission reduction of malodorous sulfur compounds from pulp mills

The authors assessed the health effects of emission reduction of malodorous sulfur compounds in a prospective cohort study with a controlled natural e xperiment. A total of 810 subjects (83%) participated in the follow up: 316 from the severely polluted, 306 from the moderately polluted, and 188 from the nonpolluted communities. in the severely polluted community, the annua l ambient air concentration of total reduced sulfur compounds decreased fro m 11 mu g/m(3) to 6 mu g/m(3). Compared with the nonpolluted community, the relative decrease in acute respiratory infections, adjusted for a change i n smoking habits, was 0.53 episodes/person-year (95% confidence interval = 0.22, 0.83) in the severely polluted community and 0.36 episodes/person-yea r (95% confidence interval = 0.06, 0.66) in the moderately polluted communi ty. In addition, the frequency of nasal symptoms (p = .004) and cough (p = .037) decreased significantly. The results are consistent with the hypothes is that exposure to malodorous sulfur compounds increases the risk of acute respiratory infections and symptoms of the respiratory tract.