Occupational exposure to hydrochloric acid in pickling of steel for remove rust or iron oxide scale from iron processing occurs at low concentration. This study aimed to investigate the respiratory symptoms and pulmonary dysfunction caused by exposure to low concentration of hydrochloric acid in acid washing unit in one of the steel industries. A case control study was carried out in the acid washing unit of the cold rolling of the steel industry in 2017. The exposed group included 45 male workers, and another 41 unexposed employees from official employees were enrolled as control group. A questionnaire was used to collect personal and occupational data and pulmonary function tests, including forced vital capacity (FVC), forced expiratory volume in the first second and peak expiratory flow rate followed guidelines given by the American Thoracic Society and measured with a portable calibrated vitalograph spirometer. For determination of acid concentration, 21 breathing zone air samples were collected in accordance with Method 7903 NIOSH. The findings showed that nose sensitivity, throat irritation and shortness of breath were the highest prevalence symptoms among exposed persons (30.4% to 32.6%). Also, the results showed that FVC and forced expiratory volume in the first second had highest and direct or positive correlation with height (0.965 and 0.927, respectively). Age and weight put in the next priorities (P < 0.01). On the other hand, based on the results of multivariate linear regression, exposing to the acid and job history are two main predictor factors for FVC. So that, the exposing to acid, by itself can reduce FVC as 4.386 units. This value is equal to 1.117 for the job history. Exposure to low concentrations of hydrochloric acid alone could increase the risk of respiratory tract damage and pulmonary function disorders. But the extent to which it can cause respiratory complications for occupational exposure is still unknown and requires further study. This study was approved by Ethical Committee of Qom University of Medical Sciences (approval No. IR.MUQ.REC.1397.118) on November 6, 2018.
Keywords: chemical industry; expiratory reserve volume; hydrochloric acid; respiratory gas; vital capacity.