the effect of exposure to low levels of chlorine gas on the pulmonary function and symptoms in a chloralkali unit

background : the present study was undertaken to ascertain whether (or not) long term occupational exposure to low (sub-tlv levels) atmospheric concentrations of chlorine gas was associated with any significant decrements in the parameters of pulmonary function and/or  increased prevalence of respiratory symptoms. methods : in this retrospective cohort study that was performed in 2012, 54 workers of a local chloralkali unit and 38 non-exposed office staff were enrolled and compared. atmospheric concentrations of chlorine gas were measured by numerous sampling with gas detector tubes. data on respiratory symptoms were gathered using a standard questionnaire. furthermore, spirometry test was performed for subjects both prior to and at the end of shift. results : mean atmospheric concentration of chlorine gas was 0.27 ±0.05 ppm that was lower than the existing tlv value for this toxic irritant gas. symptoms of respiratory diseases were significantly more frequent among exposed subjects than in referent individuals. additionally, mean values of most parameters of pulmonary function including fev 1 ( p =0.031), fev 1 /fvc ratio ( p =0.003) and pef ( p =0.005) were significantly lower than their corresponding values for unexposed subjects. additional cross shift decrements were also noted in some lung functional capacities, although changes were not statistically significant. conclusions : exposure to sub-tlv levels of chlorine gas is associated with statistically significant decrements in the parameters of pulmonary function as well as increased prevalence of respiratory symptoms.