Evaluation of the health risk associated with exposure to chloroform in indoor swimming pools

The exposure of swimmers to chloroform (CHCl3) was investigated in indoor s wimming pools of the Quebec City region along with the associated carcinoge nic risk. Six training sessions involving 52 competition swimmers (11 to 20 yr old) were conducted in 3 different pools, while 12 adult leisure swimme rs attended 5 sessions, each held in a different pool. For each session, wa ter and ambient air CHCl3 concentrations were measured and CHCl3 levels in alveolar air samples (CHCl3, ALV) collected from swimmers prior to entering the swimming pool premises and after 15, 35, and 60 min of swimming. Mean water concentrations varied from 18 mug/L to 80 mug/L, while those in air r anged from 78 mug/m(3) to 329 mug/m(3). Multiple linear regression analyses revealed that CHCl3 ALV values in competition swimmers were strongly corre lated to ambient air and water levels, and to a lesser degree to the intens ity of training. Only ambient air concentration was positively correlated t o CHCl3 ALV in the leisure group. Concentrations of CHCl3 metabolites hound to hepatic and renal macromolecules, estimated using a physiologically bas ed pharmacokinetic (PBPK) model, were 1.6 and 1.9 times higher for the comp etition swimmers than for the leisure swimmers, respectively. The highest h epatic concentration predicted in competition swimmers, 0.22 mug CHCl3 equi valents/kg of tissue, was at least 10,000 times lower than the smallest no observed effect level for liver tumors in animals. Data indicate that the s afety margin is therefore very large, for competitive swimmers as well as f or leisure swimmers.