BRONCHIAL HYPERRESPONSIVENESS CAN IMPROVE WHILE SPIROMETRY PLATEAUS 2TO 3 YEARS AFTER REPEATED EXPOSURE TO CHLORINE CAUSING RESPIRATORY SYMPTOMS

Repeated exposure to chlorine in pulp mills and paper mills can induce persistent asthma-like symptoms such as bronchial hyperresponsiveness and variable changes in airway caliber. The long-term time course of bronchial hyperresponsiveness has not been examined. We studied 20 of 29 subjects (69% participation rate) who demonstrated bronchial hyperr esponsiveness to methacholine when they were first assessed, 18 to 24 mo after repeatedly inhaling ''puffs'' of high concentrations of chlor ine in a paper mill over a 3-mo period. Each subject answered a respir atory questionnaire and underwent spirometry and a methacholine inhala tion test 12 mo after the initial survey, 30 to 36 mo after the chlori ne inhalations. Three subjects required inhaled steroids at the time o f the initial survey and three at the time of the second, including tw o who carried on using these preparations. Only one subject changed sm oking habits. There were no significant overall changes in FEV, on the two occasions, nine subjects having a FEV(1) < 80% on the first occas ion and eight on the second. Six of the 18 subjects (33%) who underwen t a methacholine inhalation test on both occasions had significantly i mproved PC20 results, including five for whom the PC20 value was withi n the normal range. All six subjects had normal FEV(1) values on both assessments. Although changes in spirometry induced by repeated exposu re to chlorine seem to persist, bronchial hyperresponsiveness can impr ove significantly in those with normal airway caliber. This suggests t hat less pronounced bronchial alterations induced by repeated exposure s to chlorine may be reversible.