Increased Concentration of Chlorine in Swimming Pool Water Causes Exercise Induced Bronchoconstriction (EIB)

Abstract

2046 PURPOSE: The purpose of this study was to assess whether chlorine exposure during swimming at the same exercise intensity in swimming pools with different chlorine levels provokes Exercise Induced Bronchoconstriction (EIB) in well-trained swimmers with and without a past history of EIB. METHODS: 21 trained swimmers with a history of EIB [H] and 20 trained swimmers with no history of EIB [NH]) completed a medical history and training questionnaire. Subjects were randomly exposed to 4 different exercise tests of the same intensity (minimum of 6–8 min at 60–80% of the target heart rate) and duration: swimming in an indoor pool with no chlorine in the water (NCL = 29), swimming in a chlorinated swimming pool with low levels of chlorine (0.5 ppm) (CL0.5 = 17), swimming in a chlorinated swimming pool with high levels of chlorine (1.0 ppm) (CL1.0 = 30), and running or cycling exercise challenge next to any one of the swimming pools (EX = 37). Spirometry was performed with a calibrated hand held spirometry before (baseline) each exercise challenge, immediately after and then at 5, 10, 15 and 30 min after the challenge test. Forced Expiratory Volume after one second (FEV1) was measured and a % fall in FEV1 >10 % during recovery compared with baseline was considered positive for EIB. RESULTS: The % subjects with a positive test for EIB was significantly higher in the CL1.0 condition (NH = 60, H = 67), compared with the CL0.5 (NH = 10, H = 0), NCL (NH = 18, H = 17), and the EX (NH = 3, H = 12) conditions. There was no difference in the frequency of EIB between the NH and NH groups. CONCLUSION: Swimmers exposed to chlorine concentrations in pool water (> 1ppm) have a higher risk of developing EIB irrespective of a past history of EIB. This finding has important implications for the testing of swimmers with suspected EIB, and exercise prescription in athletes with established EIB.