Covariation amongst pool management, trichloramine exposure and asthma for swimmers in Norway

The association between asthma and exposure to the air in swimming facilities has been acknowledged. However, the variation in, long-term exposure to and management of the respiratory irritant trichloramine (NCl3) is not well understood. In this study, 313 swimmers above 18 years of age licensed by the Norwegian Swimming Association answered a questionnaire about health and swimming. The prevalence of asthma amongst the most-exposed swimmers was 36%. Two facilities, those with the highest and lowest reported prevalence of asthma, were chosen for further investigation. For each facility, a one-week-long monitoring campaign was performed, during which pool management, air and water quality were investigated. The results of this study showed that time of day, occupancy and pool management affect the concentration of NCl3, which ranged from 58 μg/m3 to 461 μg/m3. Furthermore, in one of the facilities, the concentration of CO2 was measured to evaluate whether this contaminant could be used to predict the number of pool occupants as well as the concentration of NCl3 in the air. The concentration of CO2 was significantly correlated with occupancy level (ρ = 0.82, p = 0.01) and NCl3 concentration (r = 0.80, p = 0.01). Furthermore, according to the random intercept model the concentration of CO2 explained 52% of the variation observed in the air concentration of NCl3. CO2 sensors to control the air supply can help reduce the air concentrations of NCl3 and balance the air supply based on occupancy level. [Display omitted] •Air exposure to trichloramine in swimming facilities is associated with asthma.•No sensor for monitoring air concentrations of NCl3 exist.•The prevalence of asthma amongst the most-exposed swimmers in Norway was 36%.•CO2 concentration explained 52% of the variation observed in NCl3.•CO2 sensors can improve air quality and balance the air supply to occupancy level.