Effects of low concentrations of chlorine on pulmonary function in humans.

Eight healthy unacclimated volunteers were exposed to chlorine gas in concentrations of 0.5 or 1 ppm, and several pulmonary function measurements were made. Comparisons were made by paired t test between the percent change from base-line values obtained at various times after chlorine exposure and the percent change from base line at analogous times after a sham exposure. With the sham vs. 0.5-ppm exposure, there were trivial changes observed. Total lung capacity (TLC) was lower before 0.5-ppm exposure than before sham exposure, and the percent decrease in carbon dioxide pulmonary diffusing capacity was smaller 24 h after 0.5-ppm exposure than 24 h after sham exposure. With the sham vs. 1-ppm exposure, there were many differences in percent change from base line that were significant at the P less than 0.05 level or better. These were in forced vital capacity (FVC), forced expiratory volume at 1 s (FEV1), peak expiratory flow rate (PEFR), forced expiratory flow rate at 50 and 25% vital capacity (FEF50 and FEF25, respectively), and airway resistance (Raw). There were, in addition, significant changes after only 4 h of exposure. These were in FEV1, PEFR, FEF50, FEF25, TLC, Raw, and the difference in nitrogen concentration. Most of the test results had returned to normal by the next day. We conclude that even though chlorine at low concentrations does not produce any serious subjective symptoms, it adversely affects pulmonary function transiently.