Full-scale multisampling and empirical modeling of DBPs in water and air of indoor pools.

Disinfection by-products (DBPs) are formed in the water in swimming pools due to reactions between disinfectants (chlorine, bromine, ozone, etc.) and the organic matter introduced by bathers and supply water. High concentrations of DPBs are also reported in the air of indoor swimming pools. Based on robust multisampling programmes, the levels and variation of DBPs in the air (trichloramine [TCAM] and trihalomethanes [THMs]) and water (THM) were assessed, as well as their precursors (total organic carbon, water temperature, pH, free and total chlorine) and proxies (CO 2 and relative humidity) in four indoor chlorinated swimming pools. High-frequency sampling was conducted during one high-attendance day for each pool. The number of bathers had an important impact on the levels of THMs and TCAM, with a two-to-three-fold increase in air chloroform (up to 110 µg/m 3 ) and a two-to-four-fold increase in TCAM (up to 0.52 mg/m 3 ) shortly after pools opened. This study also focused on parameters that are easy to measure in order to develop models for predicting levels of THMs and TCAM in the air. It was shown that CO 2 and relative humidity can serve as proxies for monitoring variations in airborne THMs and TCAM. Our results highlight the good predictive capacity of the developed models and their potential for use in day-to-day monitoring. This could help optimize and control DBP formation in the air at indoor pools and reduce contaminant exposure for both pool employees and users.