Summary Chlorination disinfection byproducts (DBPs) are the inevitable result of chemical reactions between the chlorine added to swimming pool water and the organic and/or nitrogeneous matter that is naturally present or introduced by bathers. DBPs can be broken down into numerous categories and even more components (>600), which have led to concerns from legislators and scientists worldwide about the impact of these substances on workers’ health. The problems of irritation associated with exposure to chloramines (CAM) that pollute the ambient air are very often cited. However, potential health impacts related to chronic exposure to trihalomethanes (THMs) or haloacetic acids (HAAs) should not be neglected. The list of emerging disinfection byproducts keeps getting longer and we still know little about these substances, which, even in low quantities, have potentially serious toxic properties. Few studies on this subject have been carried out to date in Québec, and information about exposure of swimming pool staff to various DBPs remains very limited. In that context, two major campaigns were set up to document levels of environmental contamination (water and air) in swimming pools and biological contamination (urine and expired air) in workers, and to provide an overview of the situation. During the first campaign (A) (fall 2012), we visited 41 indoor pools in Montréal and Québec City. At these pools, concentrations of a wide range of DBPs were measured during periods of average attendance. These included (i) among classic DBPs: THMs and chloramines in both water and air, and HAAs (non-volatile) in water; (ii) among the emerging DBPs: haloacetonitriles (HAN), halonitromethanes (HNM) and haloketones (HK). These analyses were systematically accompanied by measurements of common physiochemical parameters used to characterize water quality (pH, temperature, etc.). The second campaign (B) (Spring 2013), focused on a subset of eight swimming pools chosen from among the 41 pools visited during campaign A. The levels of environmental contamination in these eight establishments were again investigated, in order to compare the findings with those observed during the first campaign, among others. At this point, N-nitrosodimethylamine (NDMA) was added to the list of DBPs assessed, while some additional measures enabled contamination levels in the air in rooms around the pool to be recorded. Workers were recruited at each of these eight swimming pools (a total of 35 subjects) to voluntarily provide urine and/or alveolar air samples. The samples were collected at time zero (when the sampling staff or the worker arrived at the site), and then again after periods of activity (and thus exposure) of variable durations. The THM concentrations in the samples were then measured. These data, particularly those concerning chloroform (TCM), were modelled to reconstruct and simulate the exposures encountered; the predictions were then validated against the field data. This made it possible for the model to be used to predict various exposure scenarios and to assess their impact on the dose absorbed. The main results of this study included the following: highly variable environmental DBP contamination levels from one pool to another (both quantitatively and in terms of speciation), which were generally relatively high compared to standards and reference values from other countries, attesting to a relatively atypical presence of bromide components; DBP contamination in the biological matrices examined, which clearly reflects previous environmental exposure, but which requires an improvement in the current sampling and analysis methods; relatively reliable predictions from the modelling tools available to reconstruct and simulate the exposure of subjects. A massive database was constituted, which could be very useful in other analytical perspectives to further explore the issue of exposure to DBPs in swimming pools. This project enables us to provide a preliminary diagnosis. Until the real risks of DBPs can be better identified, we recommend putting into practice actions that will minimize exposure, mainly through reducing their formation and encouraging their elimination. Bathers must do their part by adopting responsible hygienic behaviour (showering before swimming, wearing bathing caps, etc.). The implementation of more effective and deep-seated technical solutions (increased water and air exchange) and management of more appropriate disinfection methods (e.g., chlorine dosage strategies) should mobilize the various stakeholders and thus stimulate joint action around approaches based on an analysis of the cost-benefit ratio of interventions. With respect to research, one suggestion is that the health problems experienced by swimming pool staff in Québec be documented. Another suggestion is that an assessment of the impact of different water treatment processes on environmental contamination be carried out. Finally, with respect to management, we recommend the implementation of initiatives to adopt and apply regulatory standards for certain DBPs (e.g., THM in water, NDMA in water, CAM in air).