Objective: To describe levels of pollutants found in indoor swimming pools in Guipúzcoa (Basque Country, Spain), both in the bathing water and in the air, and to study the association between these pollutants and other variables related to ventilation systems and the use of installations.
Methods: Of the 35 indoor swimming pools registered in Guipúzcoa, the 20 most frequently used by swimmers were studied. Each installation was sampled on two nonconsecutive days. Free and combined chlorine and trihalomethane levels were measured in the water, while total chlorine and chloroform levels were measured in the air. Carbon dioxide (CO(2)) was measured as an indicator of air renewal.
Results: The average chlorine level in the air was 0.4 mg/m(3) and that of chloroform was 22 microg/m(3). In all the swimming pools, free and combined chlorine levels were within the permitted values. The average chloroform level in bathing water was 13.7 microg/l. Chloroform levels in the air could be reasonably predicted (R(2) = 0.85), the predictive factors being chloroform levels in the water, CO(2) concentrations, and the number of bathers on the day of measurement.
Conclusions: Levels of pollutants in the water and in the air of swimming pools in Guipúzcoa were lower than those reported in other studies. However, 20% of the installations exceeded the concentration of total chlorine in the air proposed as a reference value to protect swimmers carrying out intense activities (0.5 mg/m(3)).