Indoor air quality in health clubs: Impact of occupancy and type of performed activities on exposure levels

•Indoor air quality of four health clubs (HC) was assessed.•In all HC TVOCs exceeded legislative limits even when empty, thus indicative of risks.•PM1 and PM4 levels were twice higher in HC with natural ventilations.•CO2 and relative humidity were well correlated with indoor occupancy.•Cardio activities caused ∼2 higher inhalation doses, being 20% higher for females. Associations between indoor air quality (IAQ) and health in sport practise environments are not well understood due to limited knowledge of magnitude of inhaled pollutants. Thus, this study assessed IAQ in four health clubs (HC1–HC4) and estimated inhaled doses during different types of activities. Gaseous (TVOCs, CO, O3, CO2) and particulate pollutants (PM1, PM4) were continuously collected during 40 days. IAQ was influenced both by human occupancy and the intensity of the performed exercises. Levels of all pollutants were higher when clubs were occupied (p