SURVEY OF CONSTRUCTION WORKERS REPEATEDLY EXPOSED TO CHLORINE OVER A 3 TO 6 MONTH PERIOD IN A PULPMILL .2. FOLLOW-UP OF AFFECTED WORKERS BYQUESTIONNAIRE, SPIROMETRY, AND ASSESSMENT OF BRONCHIAL RESPONSIVENESS18 TO 24 MONTHS AFTER EXPOSURE ENDED

Objective-The aim was to determine the prevalence of persistent respir atory symptoms and bronchial hyper-responsiveness due to reactive airw ays dysfunction syndrome in a population of construction workers at mo derate to high Ask of developing the syndrome, at an interval of 18 to 24 months after multiple exposures to chlorine gas during renovations to a pulp and paper mill. Design and participants-71 of 289 exposed w orkers (25%) were identified on the basis of an exposure and the onset of respiratory symptoms shortly after this event (moderate to high ri sk). A standardised respiratory questionnaire was first presented, fol lowed by spirometry and a methacholine inhalation test on those whose questionnaire suggested the persistence of respiratory symptoms. Resul ts-64 of 71 (90%) subjects completed the respiratory questionnaire at the time of the follow up. The questionnaire suggested a persistence o f respiratory symptoms in 58 of the 64 workers (91%). Of the 58 subjec ts, 51 underwent spirometry and assessment of bronchial responsiveness . All of them used bronchodilators as required (not regularly) and fou r required inhaled antiinflammatory preparations. Sixteen had bronchia l obstruction (forced expiratory volume in one second) (FEV(1) < 80% p redicted) and 29 showed significant bronchial hyper-responsiveness. Co nclusion-Of the subjects (n = 71) who were at moderate to high risk of developing reactive airways dysfunction syndrome after being exposed to chlorine and were seen 18 to 24 months after exposure ended, 58 (82 %) still had respiratory symptoms, 16 (23%) had evidence of bronchial obstruction, and 29 (41%) had bronchial hyper-responsiveness.