Pulmonary Function Effects of 1.0 and 2.0 ppm Sulfur Dioxide Exposure in Active Young Male Non-Smokers

Abstract

The threshold concentration of sulfur dioxide which will induce pulmonary function changes in the normal population has not been established. To investigate this question, nine young healthy adult non-smoking males were exposed for 2 h to filtered air (FA), 1.0 ppm SO₂, and 2.0 ppm SO₂. In a follow-up study an additional 14 subjects were exposed to FA and 1.0 ppm SO₂ conditions. Forced expiratory tests were performed prior to and following the 2-h exposure, and 5 min after each of three 30-min exercise periods. The work load during the exercise periods was set to elicit a minute ventilation of 40 liters BTPS. Thoracic gas volume (TGV), airway resistance (Raw), maximal voluntary ventilation (MW), and helium dilution functional residual capacity (FRC) were also measured before and after the exposure. In the Initial subject group (n = 9), none of the spirometric tests demonstrated any significant effects to the subject from exposure to 1.0 or 2.0 ppm SO₂ either after 30 min of continuous exercise or 2 h of intermittent exercise. The only significant change (p > 0.05) was an increase in specific airway resistance (SRaw) following exposure to 1.0 or 2.0 ppm SO₂. However, when this observation was further studied in the larger (n = 23) subject group exposed to 1.0 ppm SO₂, neither SRaw nor any of the other pulmonary function tests indicated a significant effect of exposure to 1.0 ppm SO₂.